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J. Biol. Chem., Vol. 277, Issue 7, 5168-5174, February 15, 2002

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Transcriptional Regulation of the Transforming Growth Factor  Type II Receptor Gene by Histone Acetyltransferase and Deacetylase Is Mediated by NF-Y in Human Breast Cancer Cells^*

Seok Hee Park^§, Sae Ra Lee, Byung Chul Kim, Eun Ah Cho, Sejal P. Patel, Hee-Bum Kang^§, Edward A. Sausville^¶, Osamu Nakanishi, Jane B. Trepel^**, Byoung Ick Lee, and Seong-Jin Kim^§§

From the  Laboratory of Cell Regulation and Carcinogenesis, the ^¶ Developmental Therapeutics Program, and the ^** Medicine Branch, NCI, National Institutes of Health, Bethesda, Maryland 20892, the ^§ Division of Basic Science, National Cancer Center, Madu-dong, Goyang-Si, Gyeongi-do, 411-764, Korea, and  Mitsui Pharmaceuticals, Chiba 297-0017, Japan

Received for publication, July 10, 2001, and in revised form, November 14, 2001

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

Transcriptional repression of the transforming growth factor- (TGF-) type II receptor (TRII) gene is one of several mechanisms leading to TGF- resistance. Previously, we have shown that MS-275, a synthetic inhibitor of histone deacetylase (HDAC), specifically induces the expression of the TRII gene and restores the TGF- signaling in human breast cancer cell lines. However, little is known about the mechanism by which inhibition of HDAC activates TRII expression. MS-275 treatment of cells expressing a wild-type TRII promoter/luciferase construct resulted in a 10-fold induction of the promoter activity. DNA transfection and an electrophoretic mobility shift assay showed that the induction of the TRII promoter by MS-275 requires the inverted CCAAT box and its cognate binding protein, NF-Y. In addition, a DNA affinity pull-down assay indicated that the PCAF protein, a transcriptional coactivator with intrinsic histone acetyltransferase (HAT) activity, is specifically recruited to the NF-Y complex in the presence of either MS-275 or trichostatin A. Based on these results, we suggest that treatment with the HDAC inhibitor induces TRII promoter activity by the recruitment of the PCAF protein to the NF-Y complex, interacting with the inverted CCAAT box in the TRII promoter.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

The histone-modifying enzymes histone acetyltransferase (HAT)¹ and histone deacetylase (HDAC) have been proposed to play an important role in transcriptional regulation by altering chromatin structure (1, 2). HATs specifically catalyze the acetylation of the -amino group of lysine residues at the N-terminal domain of histone H2A, H2B, H3, and H4, leading to a destabilization of the nucleosome structure whereas HDACs remove the acetyl group, resulting in a compact chromatin configuration. Hyperacetylation of chromatin is generally associated with transcriptional activation, whereas hypoacetylation of chromatin is associated with transcriptional repression (3, 4). HATs and HDACs thus constitute important links between chromatin structure and transcriptional output.

Transforming growth factor  (TGF-) has been implicated in a wide variety of cellular processes, including regulation of the cell cycle, cell differentiation, and extracellular matrix synthesis (5, 6). TGF- primarily exerts its biological effects through interactions with the TGF- type II receptor (TRII) (7, 8). Much work (9-12) has shown that inactivation of TRII contributes to malignant transformation at an early step of tumorigenesis and that it can occur through mutation or transcriptional repression of the TRII gene. Interestingly, many human cancer cell lines express normal TRII and downstream signaling intermediates, but express significantly low or undetectable levels of TRII mRNA, suggesting that transcriptional repression of the TRII gene might be a more common mechanism leading to TGF- resistance (9, 13, 14).

We have previously demonstrated (15) that MS-275, a histone deacetylase inhibitor, induces the accumulation of acetylated histones in the chromatin of the TRII gene and that this induction is associated with an increase of TRII mRNA in human breast cancer cell lines, contributing to the restoration of TGF- signaling. In this study, we have expanded upon this early observation and examined the molecular mechanism of the induction of the TRII gene by MS-275 treatment in human breast cancer cell lines. We first show that the inverted CCAAT box and its cognate binding protein, NF-Y, play an important role in the induction of TRII gene expression. Second, we found that PCAF, a protein with an intrinsic HAT activity, is recruited to the NF-Y complex upon treatment with MS-275, leading to the increase of TRII gene expression. These findings demonstrate the mechanism by which the TRII gene, which is transcriptionally repressed by hypoacetylation, is induced by an HDAC inhibitor.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

Cell Culture, Transfections, and Reporter Assay-- The human breast cancer cell lines, MCF-7 and ZR-75, were cultured in RPMI 1640 medium without phenol red with 10% charcoal-treated fetal bovine serum and were incubated at 37 °C with 5% CO₂. MS-275, an inhibitor of histone deacetylase, was provided by Mitsui Pharmaceuticals (16). MCF-7 and ZR-75 cells were transfected using Lipofectin reagent (Invitrogen) according to the manufacturer's protocol. Briefly, for transient transfection, cells were seeded in six-well plates at a density of 3 × 10⁵ cells/well. The following day cells were transfected with the indicated TRII promoter construct (1.0 µg/well) or cotransfected with 1.0 µg of a TRII promoter construct and 1.0 µg of PCAF expression vector. Cells were incubated for 24 h prior to treatment with MS-275 and treated for 24 h before harvesting. For stable transfection, either pGL3-basic, pTRII 102/+2-luc, or pTRII 102/+2M4-luc (Fig. 4) was cotransfected with pCIneo (Promega) plasmids into MCF-7 cells using Fugene 6 reagent (Roche Molecular Biochemicals) according to the manufacturer's protocol. After 2 days, stable transfectants were selected using G418 (800 µg/ml; Calbiochem) for 3 weeks. Resultant colonies were picked for further analysis. Luciferase assay was performed with commercially available reagents and normalized relative to protein concentration as determined by the Bradford assay kit (Bio-Rad). All experiments were repeated at least three times with similar results.

Plasmids and Site-directed Mutagenesis-- Deletion mutants of the TRII promoter in this study were cloned into the promoterless luciferase vector (pGL3-basic) using HindIII and SacI sites. Site-directed mutagenesis of the region from 102 to 50 as shown in Fig. 4 was performed by the QuikChange site-directed mutagenesis kit (Stratagene, La Jolla, CA). The PCAF expression plasmid was kindly provided by Dr. Y. Nakatani.

RNA Extraction and Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR)-- Total RNAs were isolated with the Triazol reagent (Invitrogen) according to the manufacturer's protocol. RT was performed using the SuperScript kit (Invitrogen) according to the manufacturer's instructions. For the PCR reaction, the PCR reagent system kit from Invitrogen was used according to the manufacturer's instructions. The sequences of the luciferase primers were 5'-TCAAAGAGGCGAACTGTGTG-3' and 5'-TTTTCCGTCATCGTCTTTCC-3'. As a control, -actin primers were 5'-TTCGCGGGCGACGATGCCCCCCGGGCCGTC-3' and 5'-AGGATGCCTCTCTTGCTCTG-3'. The luciferase and -actin cDNAs were amplified in separate PCR reactions. Samples that lacked RT were also amplified to control for the presence of any contaminating genomic DNA.

Nuclear Extracts, Electrophoretic Mobility Shift Assay (EMSA), and Antibody Supershift Assay-- Preparation of nuclear extracts, EMSA, and antibody supershift assay were performed as described previously (18). MCF-7 cells were cultured with and without either MS-275 (0.5 µM) or trichostatin A (TSA; 0.3 µg/ml) for 24 h and harvested to prepare nuclear extracts. For EMSA, double-stranded oligonucleotides containing the CCAAT box region (100 to 62) (18) were labeled with [-³²P]ATP and polynucleotide kinase and purified using a 10% nondenaturing polyacrylamide gel. To perform a competition assay, unlabeled oligonucleotides were used as competitors. For the antibody supershift assay, the reactions were performed by preincubating nuclear extracts with 0.5 µg of antibody at 4 °C. The anti-NF-YA and anti-NF-YB antibodies were purchased from Santa Cruz Biotechnology, Inc (Santa Cruz, CA).

DNA Affinity Pull-down Assay-- A DNA affinity pull-down assay using M280 magnetic beads (Dynal) was performed as previously described by Sasaki et al. (19) with minor modification. Four copies of the region from 100 to 67 containing the CCAAT box were cloned into pUC18 and biotinylated by PCR, using a biotin-labeled M13 reverse primer and a non-biotin-labeled M13 forward primer. The purified PCR fragments (40 µg) were conjugated to 10 mg of M280 magnetic beads according to the manufacturer's protocol (Dynal). DNA-conjugated beads (50 µl) were mixed with 1.0 mg of MCF-7 nuclear extracts in binding buffer (10 mM Tris, pH 7.5, 100 mM NaCl, 1 mM dithiothreitol, 1 mM EDTA, 5% glycerol) for 4 h at 4 °C with constant rotation. The suspension was precipitated with a magnetic plate (Dynal MPC-S), washed in binding buffer three times, and reprecipitated with centrifugation. The bound proteins were eluted with 20 µl of BC500 buffer as described by Sasaki et al. (19). The eluted proteins were analyzed by Western blotting with anti-NF-YB and anti-PCAF antibodies (Santa Cruz Biotechnology).

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

TGF- Type II Receptor Promoter Is Activated by the HDAC Inhibitors, Including MS-275-- Because MS-275 increased the accumulation of acetylated histones H3 and H4 in the TRII promoter and induced expression of TRII mRNA in human breast cancer cell lines (15), we investigated whether the histone deacetylase inhibitors MS-275, TSA, and sodium butyrate (NaBu) activate TRII promoter activity in the MCF-7 human breast cancer cell. TRII/luciferase reporter construct (pTRII219/+35-luc), showing the strongest response to MS-275, and control vector pGL3-basic were transiently transfected and treated with MS-275 (0.5 µM), TSA (0.3 µg/ml), and NaBu (2 mM) for 24 h. As shown in Fig. 1a, TRII promoter activity was dramatically increased about 60- to 70-fold after treatment with MS-275 or TSA and about 30-fold after treatment with NaBu. No significant induction in promoter activity of the control vector (pGL3-basic) was found after treatment with the inhibitors. These results were consistent with the previous report that the HDAC inhibitor, MS-275, induces TRII gene expression at a transcriptional level.

View larger version (16K): [in this window] [in a new window]   Fig. 1.   Activation of the TRII promoter by MS-275, TSA, and sodium butyrate in MCF-7 cells. MCF-7 cells were transiently transfected with 1.0 µg of the indicated constructs and treated or not treated with 0.5 µM MS-275, 0.3 µM TSA, or 2 mM NaBu for 24 h. Luciferase activity was determined, and activities were normalized on the basis of -galactosidase expression in all luciferase reporter experiments. The data represent three independent experiments performed in triplicate.

Several reports have shown that only promoters that are integrated into the chromosome could be regulated by HATs and HDACs, whereas several other reports have shown that the activity of transiently transfected promoters could be efficiently modulated by HATs and HDACs (20-25). Therefore, we constructed stable cell lines expressing the TRII promoter/reporter gene to examine whether the TRII promoter/reporter gene stably integrated into chromosomal DNA is also regulated by HATs and HDACs. The MCF-7 cell line was transfected with either the TRII/luciferase reporter constructs (pTRII102/+2-luc or pTRII102/+2M4-luc) or its control vector as described under "Materials and Methods," and stable transfectants were selected. The cell lines in which either the pTRII102/+2-luc or pTRII102/+2M4-luc gene were stably integrated were treated with 0.5 µM MS-275 for 24 h. As a control, the stable cell line, which contained pGL3-basic, a promoterless luciferase vector, was also treated with MS-275 under the same conditions. Expression of the luciferase gene was studied by RT-PCR. As shown in Fig. 2a, a DNA band of about 328 bp corresponding to a luciferase fragment of expected size was detected in MCF-7 cell lines. However, the level of luciferase expression in cell lines expressing control vector and pTRII102/+2M4-luc was very low, and MS-275 treatment did not increase the expression level. In the stable cell lines expressing pTRII102/+2-luc gene, the activity of the TRII promoter was increased ~5-fold following treatment with MS-275 (Fig. 2a). The pTRII102/+2-luc stable cell lines showed higher basal luciferase activity, and MS-275 treatment further induced its luciferase activity (Fig. 2b). These results indicate that MS-275 has the same effect in stable cell lines expressing the TRII promoter/luciferase gene as in cells expressing the transiently transfected TRII promoter.

View larger version (50K): [in this window] [in a new window]   Fig. 2.   Activation of stably integrated TRII promoter by MS-275. MCF-7 cells were stably transfected with either TRII promoter-luciferase reporter construct (pTRII102/+2), pTRII 102/+2M4 mutant, or with vector alone (pGL3-basic). The cells were treated or not treated with MS-275 (0.5 µM) for 24 h. Luciferase induction was examined by RT-PCR (a) and luciferase activity (b). The expected luciferase fragment of ~328 bp was amplified from total RNAs from stable cell lines. As a control, the -actin band of ~134 bp was also amplified from all samples. No DNA fragment could be amplified from cDNA samples that lacked reverse transcriptase (no RT), indicating that the amplified bands were derived from mRNA. Luciferase activity of lysed cells was measured and normalized against protein concentration. The data represent three independent experiments performed in triplicate.

An Inverted CCAAT Box Plays an Important Role in Activation of the TRII Promoter by MS-275-- To characterize the promoter region responsible for the induction of the TRII promoter by MS-275, serial deletion mutants of the TRII promoter, as shown in Fig. 3, were transiently transfected into MCF-7 and ZR-75 breast cancer cell lines, and the cells were then treated with MS-275. When the promoter was deleted to 172, induction of the TRII promoter by MS-275 was decreased to 50% in both cell lines, suggesting the presence of an element responsible for the induction within the region from 219 to 172. Interestingly, deletion of the region from 100 to 47 dramatically decreased the induction of the TRII promoter to only about 2-fold upon treatment of MS-275, whereas expression of pTRII100/+35-luc was still induced ~20-fold (Fig. 3). These results suggest that the region from 100 to 47 contains a major element(s) required for the induction by MS-275. Therefore, the region from 100 to 47 was focused on in order to study the mechanism of MS-275-mediated induction of the TRII promoter.

View larger version (20K): [in this window] [in a new window]   Fig. 3.   Activation of TRII promoter deletion constructs by MS-275 in MCF-7 and ZR-75 cells. The schematic diagrams of TRII promoter deletion constructs are shown in the left panel. TRII deletion promoters were inserted into the pGL3-basic vector directly upstream of the luciferase gene. ZR-75 (a) cells and MCF-7 (b) cells were transiently transfected with 1.0 µg of indicated constructs and treated or not treated with MS-275 (0.5 µM) for 24 h. Luciferase activity was determined, and activities were normalized on the basis of -galactosidase expression in all luciferase reporter experiments. The data represent three independent experiments performed in triplicate.

To further investigate the MS-275 responsive sequence between 100 and 47, we constructed site-directed mutants within this region, as shown in Fig. 4. Following transfection, the MCF-7 cells were exposed to MS-275 for 24 h and analyzed for luciferase activity. As shown in Fig. 4b, M3 and M4 mutants were only slightly affected by treatment with MS-275, whereas the wild type and other mutants of the TRII promoter were dramatically induced. M3 and M4 contain mutations of the inverted CCAAT box (82 to 78), which had previously been reported to be involved in v-SRC-mediated induction of the TRII promoter (18). Thus, two different mutations in the CCAAT box abolished promoter activity induced by MS-275, indicating that this CCAAT box plays a critical role in the induction of the TRII promoter by the HDAC inhibitor, MS-275.

View larger version (18K): [in this window] [in a new window]   Fig. 4.   Identification of the CCAAT box element required for MS-275 induction of the TRII promoter. a, sequences for the sense strand for a series of base substitution mutants. b, the indicated base substitution mutants were generated by the QuikChange site-directed mutagenesis kit (Stratagene) using pTRII-100/+35 as a template. These constructs were transfected into MCF-7 cells and treated or not treated with MS-275 (0.5 µM). Mutation of the inverted CCAAT box decreases TRII promoter activation by MS-275. WT, wild type.

NF-Y Protein Binds to the Inverted CCAAT Box and Its Binding Activity Is Not Changed by MS-275-- To identify specific binding of proteins to the sequences from 100 to 62, EMSA was performed as described above using a double-stranded ³²P-labeled oligonucleotide containing the sequences between 100 and 62. The reaction mixture was then electrophoresed on a polyacrylamide gel and viewed by autoradiography (Fig. 5). In the absence of unlabeled competitor oligonucleotide (Fig. 5b, lane 1), three strong bands (complexes a, b, and c) were apparent. It is clear that these bands represent specific binding of protein(s) to the target oligonucleotide sequence because binding to the labeled probe diminishes with a wild-type unlabeled competitor (Fig. 5b, lane 2). Mutant oligonucleotides derived from the sequences between 100 and 62 were used to identify the target sequences for complexes a, b, and c (Fig. 5a). M1 and M2 mutants failed to compete for binding to these complexes, whereas the M3 mutant decreased competition for binding to all three complexes (Fig. 5b, lanes 3-5). This region contains the inverted CCAAT consensus sequences. The binding of complexes a, b, and c to the M3 mutant was also markedly reduced (Fig. 5c).

View larger version (41K): [in this window] [in a new window]   Fig. 5.   Identification of the nuclear proteins (complexes a, b, and c) that bind to the MS-275 responsive element (sequence from 100 to 62) of the human TRII promoter. a, sequences for the sense strand of the mutant oligonucleotides. b, competition assay was performed with labeled oligonucleotides from 100 to 62 and MCF-7 nuclear extracts. Competitions were performed with a 50-fold excess of the indicated unlabeled oligonucleotides. Lanes 2-5 show competition with unlabeled wild type (WT), M1 mutant sequence, M2 mutant sequence, and M3 mutant sequence, respectively. The resulting DNA-protein complexes were resolved by native polyacrylamide gel electrophoresis and autoradiographed. Three major bands are visualized (a, b, and c). c, EMSA was also performed with labeled WT, M1, M2, and M3 oligonucleotides and nuclear extracts of MCF-7 (lanes 2-5).

To characterize which transcription factors interact with the CCAAT box in response to MS-275, an EMSA was performed with MCF-7 nuclear extracts prepared from MS-275 treated or untreated cells. Three protein-DNA complexes (complexes a, b, and c) from MCF-7 cells interacted with a 34-mer oligonucleotide probe of the region around the wild-type CCAAT box (Fig. 6a). Treatment with MS-275 prior to preparation of nuclear extract had no apparent effect on the complex formation (Fig. 6a). EMSA with the nuclear extract of ZR-75 human breast cancer cells showed the same protein-DNA complexes, which again were not affected by MS-275 treatment (data not shown). In addition, competition assay showed that all three protein-DNA complexes were specific to the inverted CCAAT box (Fig. 6a). The addition of unlabeled oligonucleotides containing wild-type CCAAT box sequences completely abolished the formation of all three complexes, whereas both unlabeled M4 oligonucleotides containing the mutation of the CCAAT box and nonspecific oligonucleotides did not affect complex formation (Fig. 6a).

View larger version (56K): [in this window] [in a new window]   Fig. 6.   Binding of NF-Y to the CCAAT box mediates MS-275 induction. a, 32P-labeled wild-type oligonucleotide was incubated with nuclear extracts prepared from untreated MCF-7 (lanes 2-5) and treated MCF-7 (lanes 6-9) with the indicated competitors (50-fold). ESE is an ERT promoter-specific element (31). b, for antibody supershift assay, the oligonucleotides containing the inverted CCAAT box were incubated either with 10 µg of nuclear extracts of MCF-7 treated with MS-275 alone (lane 2), with normal goat IgG (lane 3), with 0.5 µg of anti-NF-YA (lane 4), with 0.5 µg of anti-NF-YB (lane 5), or with 0.5 µg of anti-C/ERP (lane 6), respectively. Arrows indicate the supershifted bands.

To identify transcription factors interacting with this inverted CCAAT box in the TRII promoter, antibody supershift assays were performed. Because it had been reported previously (18) that the NF-Y protein binds to the CCAAT box of the TRII promoter, we determined whether the NF-Y protein interacts with the CCAAT box in MCF-7 breast cancer cell lines. NF-Y is a complex composed of three subunits, NF-YA (CBF-B), NF-YB (CBF-A), and NF-YC (CBF-C), which are highly conserved throughout evolution, and all are required for DNA binding (26-28). As shown in Fig. 6b, the NF-YA and NF-YB antibodies were found to selectively supershift the complex a in both MS-275-untreated and -treated nuclear extracts, whereas the antibody against the other CCAAT box-binding protein, C/EBP, did not show any shifted band. Interestingly, complexes b and c were not changed by the supershift assay, suggesting that these complexes are formed by other nuclear proteins. Consequently, these results indicate that complex a represents the NF-Y protein bound to the CCAAT boxes of the TRII promoter in human breast cancer cell lines and that the binding activity of NF-Y protein is not affected by MS-275 treatment. However, we do not yet understand the reason why the supershifted band by NF-YA has lower mobility than by NF-YB.

PCAF Is Only Recruited to NF-Y upon Treatment with an Inhibitor of HDAC-- These results, however, did not clearly reveal the mechanism of induction of the TRII promoter by MS-275 because binding of the NF-Y protein was not changed in MCF-7 nuclear extracts, whether untreated or treated by MS-275. Recent reports show that the NF-Y protein is connected with histone acetyltransferase activity (24, 29, 30). It was reported that the NF-Y complex possesses histone acetyltransferase activity through physical association with the related histone acetyltransferases, human GCN5 and PCAF, in vivo (29). In two other reports, TSA, a potent inhibitor of HDAC, increased the activity of NF-Y-dependent promoters such as human MDR1 and Xenopus HSP70 in vivo (24, 30). In the case of the MDR1 gene, overexpression of PCAF with intrinsic histone acetyltransferase activity induced the wild-type MDR1 promoter but not a promoter containing a mutation in the CCAAT box. Moreover, it was shown that NF-YA interacts with PCAF in vitro. In the HSP70 promoter it was reported that NF-YB is a substrate of p300 acetylation and recruits p300 to modulate transcriptional activity (30).

To investigate whether the NF-Y complex is truly involved in recruiting histone acetyltransferase activity to the TRII promoter in response to either MS-275 or TSA, a DNA affinity pull-down assay was performed. Four copies of the region containing the wild-type CCAAT box were conjugated with magnetic beads and incubated with nuclear extracts of MCF-7 cells, which were treated or untreated with either MS-275 or TSA. As a negative control, four copies of the region in which the CCAAT box was mutated were simultaneously conjugated. Bound materials were eluted, and immunoblot analysis was performed with PCAF, NF-Y, and p300 antibodies. Interestingly, only PCAF, not p300, was detected in the nuclear extracts treated with MS-275 and NF-Y protein bound to the wild-type CCAAT box, not the mutant CCAAT box (Fig. 7a). However, we could not observe the presence of PCAF in untreated cells. This result suggests a novel mechanism for the activation of the TRII promoter by an inhibitor of HDAC in human breast cancer cell lines. In the absence of either MS-275 or TSA treatment, NF-Y does not interact with PCAF in breast cancer cell lines, whereas PCAF is recruited to the NF-Y complex upon treatment with either MS-275 or TSA, increasing the activity of the TRII promoter.

View larger version (39K): [in this window] [in a new window]   Fig. 7.   PCAF is recruited to the CCAAT box by treatment with either MS-275 or TSA. a, either MS-275 or TSA treatment enhances the NF-YA and PCAF interaction. A DNA affinity pull-down assay was performed using nuclear extracts prepared from MCF-7 treated or not treated with either MS-275 or TSA. Extracts were subjected to DNA-conjugated beads followed by immunoblotting with an anti-PCAF or anti-NF-YA antibody. Expression of PCAF and NF-YA was confirmed in the nuclear extracts (lanes 1-2). b, P/CAF, not p300, is involved in TRII promoter activation. 1.0 µg of wild type (102/+2 WT-luc), CCAAT mutant (102/+2 M4-luc), or M5 mutant was transfected into MCF-7 cells with or without 1 µg of PCAF or p300 expression vector. Luciferase activity was determined, and activities were normalized on the basis of -galactosidase expression in all luciferase reporter experiments. The data represent three independent experiments performed in triplicate.

To further support the possibility that PCAF is involved in the activation of the TRII promoter in human breast cancer cell lines, a plasmid expressing PCAF was cotransfected with a wild-type (pTRII102/+2-luc) or CCAAT-mutated (pTRII102/+2M4-luc) TRII promoter/luciferase construct into MCF-7 cells. Although transfection of PCAF increased the activity of the wild-type TRII promoter about 5-fold, it had no effect on the CCAAT box mutant (Fig. 7b). However, expression of p300 did not increase the activity of the wild-type TRII promoter in MCF-7 breast cancer cells (data not shown). Consequently, our results strongly suggest that activation of the TRII promoter by an inhibitor of HDAC is due to the increase of HAT activity by recruiting PCAF to NF-Y tethered to the TRII promoter in human breast cancer cell lines.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

Several studies demonstrate that transcriptional repression of the TGF- type II receptor gene is one of several mechanisms leading to TGF- resistance. Many human cancer cell lines harbor a normal TRII gene and downstream signaling proteins but express significantly reduced or undetectable levels of TRII mRNA (9, 13). Transcriptional regulation of TRII gene expression plays an important role in modulating TGF- responsiveness. Transformation of cells by the product of the adenovirus E1A gene or overexpression of cyclin D1 in epithelial cells has been associated with down-regulation of TRII expression and TGF- resistance (32-34). Recently, we reported (12) that the Ewing sarcoma EWS-Fli1 fusion gene suppresses transcription of the TRII gene. These results imply that the TRII gene acts as a tumor suppressor gene and may be a candidate target for cancer therapy of therapeutic targets for cancer.

We have previously reported that MS-275, a HDAC inhibitor, enhances TRII gene expression in association with an accumulation of acetylated histones H3 and H4 with the TRII promoter and restores TGF- signaling in human breast cancer cell lines, suggesting the possibility that histone deacetylation of the TRII gene is a new epigenetic mechanism to contribute to the resistance of human breast cancer cell lines to TGF- (15). In this report, we have investigated the mechanism of the induction of the TRII gene by an inhibitor of HDAC in human breast cancer cell lines. First, the induction of the TRII gene by MS-275 requires an intact CCAAT box and its cognate binding factor, the NF-Y complex. Second, when cells are treated with an inhibitor of HDAC, PCAF with histone acetyltransferase activity is recruited into the NF-Y complex, increasing the activity of the TRII promoter.

Our findings that the CCAAT box and NF-Y are required for activation of the TRII promoter are similar to the data described in the induction of the MDR1 gene by TSA (24) and consistent with previous reports (29) that NF-Y is connected with histone acetyltransferase activity through physical association with human GCN5 and PCAF. However, the study of MDR1 did not clearly provide the mechanism of the induction of the MDR1 gene by TSA. They showed that PCAF interacts with NF-YA in vitro, suggesting that the direct interaction of PCAF and NF-YA mediate the transcriptional activation. Interestingly, the interaction of PCAF and the NF-Y complex on the TRII promoter was only shown in the presence of MS-275 treatment (Fig. 7a). Under normal conditions, NF-YA tethered to the TRII promoter did not interact with PCAF in the human breast cancer cell line. Upon treatment with either MS-275 or TSA, the interaction between the two proteins was increased as shown in the DNA affinity pull-down assay (Fig. 7a), whereas the DNA binding activity of the NF-Y complex was not changed in the absence or presence of an inhibitor of HDAC treatment. These findings suggest a novel mechanism for the activation of the TRII promoter by an inhibitor of the HDAC. One possibility is that transcription of the TRII promoter is repressed by a compact chromatin structure, which is maintained by increased HDAC activity in human breast cancer cell lines. However, MS-275 treatment leads to a local disruption of nucleosome structure of the TRII promoter by acetylation of H3 or H4 histones, permitting PCAF with its intrinsic HAT activity to be recruited into the NF-Y complex, resulting in the increase of TRII promoter activity. A second possibility is based on the finding that NF-YB and NF-YC contain a histone-like motif (27, 35) and interact in a nucleosome-like structure. That is, the histone-like motifs of NF-YB and NF-YC could themselves be a target for an inhibitor of HDAC. It is possible that treatment of an inhibitor of HDAC increases the state of acetylation of NF-YB and NF-YC and causes disruption of the nucleosome structure. In this manner, the acetylation of NF-YB and NF-YC may also contribute to the recruitment of PCAF to the NF-Y complex.

This is the first report showing the mechanism of the activation of the TRII promoter by a histone deacetylase inhibitor in human breast cancer cell lines. In conclusion, our present studies suggest that PCAF is recruited to NF-Y, which binds to the inverted CCAAT box in the TRII promoter and plays an important role in the activation of the TRII promoter by treatment with an inhibitor of HDAC.

	ACKNOWLEDGEMENT

We thank Dr. Anita Roberts for helpful discussion and critical review of the manuscript.

	FOOTNOTES

^* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Present address: Inha University School of Medicine, Inchon, Korea.

^§§ To whom correspondence should be addressed: Laboratory of Cell Regulation and Carcinogenesis, NCI, National Institutes of Health, Bethesda, MD 20892-5055. Tel.: 301-496-8350; Fax: 301-496-8395; E-mail: kims@dce41.nci.nih.gov.

Published, JBC Papers in Press, December 13, 2001, DOI 10.1074/jbc.M106451200

	ABBREVIATIONS

The abbreviations used are: HAT, histone acetyltransferase; HDAC, histone deacetylase; TGF-, transforming growth factor-; TRII, TGF- type II receptor gene; MS-275, N-(2-aminophenyl)-4-[N-(pyridine-3-yl-methoxy-carbonyl)aminomethyl]benzamide; TSA, trichostatin A; RT, reverse transcriptase; EMSA, electrophoretic mobility shift assay; NaBu, sodium butyrate.

	REFERENCES

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