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

Transcriptional repression of the transforming growth factor-β (TGF-β) type II receptor (TβRII) gene is one of several mechanisms leading to TGF-β resistance. Previously, we have shown that MS-275, a synthetic inhibitor of histone deacetylase (HDAC), specifically induces the expression of theTβRII gene and restores the TGF-β signaling in human breast cancer cell lines. However, little is known about the mechanism by which inhibition of HDAC activates TβRII expression. MS-275 treatment of cells expressing a wild-type TβRIIpromoter/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 TβRIIpromoter 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 TβRII promoter activity by the recruitment of the PCAF protein to the NF-Y complex, interacting with the inverted CCAAT box in the TβRIIpromoter.

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 Nterminal 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 (T␤RII) (7,8). Much work (9 -12) has shown that inactivation of T␤RII contributes to malignant transformation at an early step of tumorigenesis and that it can occur through mutation or transcriptional repression of the T␤RII gene. Interestingly, many human cancer cell lines express normal T␤RII and downstream signaling intermediates, but express significantly low or undetectable levels of T␤RII mRNA, suggesting that transcriptional repression of the T␤RII 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 T␤RII gene and that this induction is associated with an increase of T␤RII 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 T␤RII 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 T␤RII 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 T␤RII gene expression. These findings demonstrate the mechanism by which the T␤RII gene, which is transcriptionally repressed by hypoacetylation, is induced by an HDAC inhibitor.

MATERIALS AND METHODS
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% CO 2 . 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 ϫ 10 5 cells/well. The following day cells were transfected with the indicated * The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
T␤RII promoter construct (1.0 g/well) or cotransfected with 1.0 g of a T␤RII promoter construct and 1.0 g 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, pT␤RII Ϫ102/ϩ2-luc, or pT␤RII Ϫ102/ϩ2M4-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 g/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 T␤RII 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 Ϫ102 to Ϫ50 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 5Ј-TCAAA-GAGGCGAACTGTGTG-3Ј and 5Ј-TTTTCCGTCATCGTCTTTCC-3Ј. As a control, ␤-actin primers were 5Ј-TTCGCGGGCGACGATGCCCCCC-GGGCCGTC-3Ј and 5Ј-AGGATGCCTCTCTTGCTCTG-3Ј. 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 M) or trichostatin A (TSA; 0.3 g/ml) for 24 h and harvested to prepare nuclear extracts. For EMSA, double-stranded oligonucleotides containing the CCAAT box region (Ϫ100 to Ϫ62) (18) were labeled with [␥-32 P]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 g 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 Ϫ100 to Ϫ67 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 g) were conjugated to 10 mg of M280 magnetic beads according to the manufacturer's protocol (Dynal). DNA-conjugated beads (50 l) 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 l 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).  Fig. 1a, T␤RII 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 T␤RII gene expression at a transcriptional level.

TGF-␤ Type II Receptor Promoter Is Activated by the HDAC
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 T␤RII promoter/ reporter gene to examine whether the T␤RII 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 T␤RII/luciferase reporter constructs (pT␤RIIϪ102/ ϩ2-luc or pT␤RIIϪ102/ϩ2M4-luc) or its control vector as described under "Materials and Methods," and stable transfectants were selected. The cell lines in which either the pT␤RIIϪ102/ϩ2-luc or pT␤RIIϪ102/ϩ2M4-luc gene were stably integrated were treated with 0.5 M 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 pT␤RIIϪ102/ϩ2M4-luc was very low, and MS-275 treatment did not increase the expression level. In the stable cell lines expressing pT␤RIIϪ102/ϩ2-luc gene, the activity of the T␤RII promoter was increased ϳ5-fold following treatment with MS-275 (Fig. 2a). The pT␤RIIϪ102/ϩ2-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 T␤RII promoter/luciferase gene as in cells expressing the transiently transfected T␤RII promoter.
An Inverted CCAAT Box Plays an Important Role in Activation of the T␤RII Promoter by MS-275-To characterize the promoter region responsible for the induction of the T␤RII promoter by MS-275, serial deletion mutants of the T␤RII 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 Ϫ172, induction of the T␤RII 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 Ϫ219 to Ϫ172. Interestingly, deletion of the region from Ϫ100 to Ϫ47 dramatically decreased the induction of the T␤RII promoter to only about 2-fold upon treatment of MS-275, whereas expression of pT␤RIIϪ100/ϩ35luc was still induced ϳ20-fold (Fig. 3). These results suggest that the region from Ϫ100 to Ϫ47 contains a major element(s) required for the induction by MS-275. Therefore, the region from Ϫ100 to Ϫ47 was focused on in order to study the mechanism of MS-275-mediated induction of the T␤RII promoter.
To further investigate the MS-275 responsive sequence between Ϫ100 and Ϫ47, 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 T␤RII promoter were dramatically induced. M3 and M4 contain mutations of the inverted CCAAT box (Ϫ82 to Ϫ78), which had previously been reported to be involved in v-SRC-mediated induction of the T␤RII 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 T␤RII promoter by the HDAC inhibitor, MS-275.
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 Ϫ100 to Ϫ62, EMSA was performed as described above using a doublestranded 32 P-labeled oligonucleotide containing the sequences between Ϫ100 and Ϫ62. The reaction mixture was then elec-trophoresed 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 Ϫ100 and Ϫ62 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][4][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).
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 wildtype 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).
To identify transcription factors interacting with this inverted CCAAT box in the T␤RII 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 The expected luciferase fragment of ϳ328 bp was amplified from total RNAs from stable cell lines. As a control, the ␤-actin band of ϳ134 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.
T␤RII 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 T␤RII 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 T␤RII 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 T␤RII 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 mag- netic 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 T␤RII 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 T␤RII promoter.
To further support the possibility that PCAF is involved in the activation of the T␤RII promoter in human breast cancer cell lines, a plasmid expressing PCAF was cotransfected with  (complexes a, b, and c) that bind to the MS-275 responsive element (sequence from ؊100 to ؊62) of the human T␤RII promoter. a, sequences for the sense strand of the mutant oligonucleotides. b, competition assay was performed with labeled oligonucleotides from Ϫ100 to Ϫ62 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). 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 DNAconjugated 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 T␤RII promoter activation. 1.0 g of wild type (Ϫ102/ϩ2 WT-luc), CCAAT mutant (Ϫ102/ϩ2 M4-luc), or M5 mutant was transfected into MCF-7 cells with or without 1 g 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. a wild-type (pT␤RIIϪ102/ϩ2-luc) or CCAAT-mutated (pT-␤RIIϪ102/ϩ2M4-luc) T␤RII promoter/luciferase construct into MCF-7 cells. Although transfection of PCAF increased the activity of the wild-type T␤RII 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 wildtype T␤RII promoter in MCF-7 breast cancer cells (data not shown). Consequently, our results strongly suggest that activation of the T␤RII promoter by an inhibitor of HDAC is due to the increase of HAT activity by recruiting PCAF to NF-Y tethered to the T␤RII promoter in human breast cancer cell lines. DISCUSSION 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 T␤RII gene and downstream signaling proteins but express significantly reduced or undetectable levels of T␤RII mRNA (9,13). Transcriptional regulation of T␤RII 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 T␤RII expression and TGF-␤ resistance (32)(33)(34). Recently, we reported (12) that the Ewing sarcoma EWS-Fli1 fusion gene suppresses transcription of the T␤RII gene. These results imply that the T␤RII 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 T␤RII gene expression in association with an accumulation of acetylated histones H3 and H4 with the T␤RII promoter and restores TGF-␤ signaling in human breast cancer cell lines, suggesting the possibility that histone deacetylation of the T␤RII 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 T␤RII gene by an inhibitor of HDAC in human breast cancer cell lines. First, the induction of the T␤RII 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 T␤RII promoter.
Our findings that the CCAAT box and NF-Y are required for activation of the T␤RII 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 T␤RII promoter was only shown in the presence of MS-275 treatment (Fig. 7a). Under normal conditions, NF-YA tethered to the T␤RII 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 T␤RII promoter by an inhibitor of the HDAC. One possibility is that transcription of the T␤RII pro-moter 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 T␤RII 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 T␤RII 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 T␤RII 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 T␤RII promoter and plays an important role in the activation of the T␤RII promoter by treatment with an inhibitor of HDAC.