A 110-kDa retinoblastoma gene product (pRb) is a nuclear phosphoprotein that operates as a cell cycle regulator and as a major target of the oncoproteins of several DNA tumor viruses such as adenovirus E1A and papilloma virus E7(1, 2, 3, 4, 5, 6) . Only the nonphosphorylated or the hypophosphorylated form of pRb, which predominates during the G phase in the cell cycle, can bind to transcriptional factor E2F (7) and inhibits the exit from G(8, 9) . pRb is phosphorylated by cyclin-dependent kinases in the late G phase (10, 11) , resulting in the dissociation of the E2F-pRb complex and the activation of E2F-dependent promoters. The viral oncoprotein E1A can bind to the E2F binding region of pRb, thus abrogating the suppressive function of pRb. The E1A or SV40 large T binding region of pRb has been mapped to the two nonconsecutive segments, referred to as the A pocket (residues 373-579) and B pocket (residues 640-771)(3, 12, 13) .

The C-terminal region of pRb, downstream from the A/B pockets, is also known to be a site for mediating protein-protein interactions(14) . One of the proteins that can bind to this region (residues 768-928) in pRb is a nuclear c-Abl tyrosine kinase(15) . Although the c-Abl-pRb interaction is not affected by viral oncoproteins, it is disrupted by the phosphorylation of pRb during cell cycle progression. Recently it was suggested that the N-terminal region of pRb may also interact with some proteins, although no such protein has been definitively identified yet.

We reported previously that pRb could be associated in vivo with 73-kDa heat shock cognate protein (hsc73) ()in TYK-nu human ovarian carcinoma cells and in HeLa cervical carcinoma cells and that this complex could be dissociated in the presence of ATP(16) . We further analyzed the molecular interaction and mapped the hsc73 binding region of pRb. In this report we show that hsc73 can bind directly to an N-terminal region outside the pockets (residues 301-372 adjacent to the N-terminal boundary of the A pocket) and that phosphorylation of pRb inhibits this association in vitro and perhaps in vivo.

MATERIALS AND METHODS

Expression and Purification of Intact pRb Using the Baculovirus System

Purification of pRb was done by column chromatography using phosphocellulose (stepwise elution with 0.1, 0.25, 0.5, 0.75, and 1.0 M NaCl), heparin-Sepharose (stepwise elution with 0.1, 0.25, 0.5, and 1.0 M NaCl), and Q-Sepharose (stepwise elution with 0.05, 0.1, 0.3, 0.5, and 1.0 M NaCl). Fractions containing pRb were determined by staining with Coomassie Brilliant Blue or Western blotting as described in a previous paper. ()

Purified Proteins and Antibodies

In Vitro Binding Assay, Immunoprecipitation, and Immunoblotting

ATP-dependent Dissociation of pRb and hsc73

Construction of GST-pRb Deletion Mutants Expression Vector

Expression and Purification of GST Fusion Proteins

For recovery of fusion proteins using glutathione-Sepharose beads (Pharmacia), bacterial cultures were pelleted by centrifugation at 8,000 g for 20 min at 4 °C and were resuspended in 40 ml of sonication buffer (100 ml Tris-HCl (pH 7.6), 10 ml of EDTA, 0.5 ml of phenylmethylsulfonyl fluoride, 1 mg/ml lysozyme). The pellets were then lysed on ice by a mild sonication followed by centrifugation at 10,000 g for 15 min at 4 °C. Aliquots (1 ml) of supernatants were incubated for 3 h at 4 °C with 25 µl of glutathione-Sepharose beads that had been washed three times with phosphate-buffered saline. After the incubation the beads were washed three times with phosphate-buffered saline to remove nonspecific binding proteins.

In Vitro Kinase Assay

In Vivo Assessment of hsc73 Association with Nonphosphorylated Form of pRb

RESULTS

Association of hsc73 and pRb in Vitro and Dissociation by ATP

Figure 1: Panel A, pRb production and purification. Intact pRb was produced using the baculovirus system and purified by several steps of column chromatography as described under ``Materials and Methods.'' Purified pRb (approximately 1 µg) was run on SDS-PAGE and stained with Coomassie Brilliant Blue (lane 1). Lane 2 shows the molecular size makers. Panel B, direct binding of pRb to hsc73. The mixture of purified pRb (3 µg) and hsc73 (2 µg) was subjected to the immunoprecipitation with anti-pRb Mh-Rb-02P (lanes 1 and 4), anti-hsc73 3a3 (lanes 2 and 5), and isotype (IgG1)-matched control anti-109 (lanes 3 and 6) mAbs. Approximately 10 µl of these immunoprecipitates per lane was resolved by 8% SDS-PAGE and analyzed by immunoblotting with anti-pRb Mh-Rb-02P mAb (lanes 1-3) and anti-hsc73 3a3 mAb (lanes 4-6). Then the membranes were washed with 0.1% Tween 20 and phosphate-buffered saline and were reacted with peroxidase-conjugated goat anti-mouse IgG + IgM diluted at 1:1,000. The band detection was performed by developing for 30 s at room temperature with ECL detection reagents. The bands corresponding to pRb (110 kDa) and hsc73 (73 kDa) are indicated. An 80-kDa band in lane 6 might be residual intact immunoglobulins of 109 mAb whose disulfide bonds were not cleaved as yet.

Then the mixture of this purified pRb and hsc73 was subjected to immunoprecipitation. pRb was immunoprecipitated with anti-pRb mAb (Mh-Rb-02P), resolved by 8% SDS-PAGE, and analyzed by immunoblotting with anti-pRb mAb or anti-hsc73 mAb. As shown in Fig. 1B, anti-pRb mAb precipitated pRb having a molecular mass of 110 kDa (lane 1). Anti-hsc73 mAb (3a3) detected a 73-kDa protein in the pRb immunoprecipitates (lane 4). Thus, purified hsc73 appeared to be coprecipitated with purified pRb.

To confirm further the direct association of these proteins, hsc73 was precipitated with anti-hsc73 mAb and analyzed by immunoblotting with anti-pRb mAb (lane 2) or anti-hsc73 mAb (lane 5). Coimmunoprecipitation of pRb with hsc73 was also observed (lane 2). As a negative control, we used an isotype-matched 109 mAb (IgG1) that reacts to 86-kDa antigen. 109 mAb could not form immune complexes with hsc73 or pRb (lanes 3 and 6).

Since the in vivo hsc73-pRb complex recovered from cell lysates had been proven previously to be dissociated in the presence of ATP(16, 26) , we tested the ATP-dependent dissociation of the complex formed in vitro with purified proteins. An equal molar ratio of pRb and hsc73 was mixed, followed by the addition of ATP, ADP, or ATPS. Then the immunoprecipitates made with anti-pRb mAb were analyzed by immunoblotting with anti-hsc73 mAb. As shown in Fig. 2, the addition of ATP resulted in the dissociation of hsc73 from the complex (lane 3). Furthermore, it is noted that the addition of the nonhydrolyzable ATP analog ATPs resulted in considerable dissociation of the complex (lane 5). In contrast, ADP could not dissociate hsc73 from the complex (lane 4). There was no difference in the concentration of ATP required for the dissociation between the complex formed in vivo(25) and that formed in vitro with purified proteins.

Figure 2: ATP-dependent dissociation of pRb and hsc73. After 10 mM ATP (lane 3), ADP (lane 4), and ATPS (lane 5), or no nucleotide (lane 2) was added into the purified pRb (3 µg) and hsc73 (2 µg) protein mixture, they were immunoprecipitated by anti-pRb Mh-Rb-02P mAb. The immunoprecipitates were resolved by 8% SDS-PAGE and analyzed by immunoblotting with anti-hsc73 3a3 mAb. Lane 1 shows hsc73 alone containing approximately 1 µg of protein for a positive control. The bands were detected by developing for 15 s with ECL detection reagents. An 80-kDa band in lane 6 is described in the legend to Fig. 1A.

Specificity of the Interaction of hsc73 and pRb

Figure 3: Specificity of pRb-hsc73 protein interactions. Purified hsc73 (lanes 1 and 5), m65hsp (lanes 2 and 6), or hsp90 (lane 3 and 7) was incubated with approximately 3 µg of purified pRb at an equal molar ratio. The mixture was immunoprecipitated by anti-pRb Mh-Rb-02P mAb (lanes 1-7). The immunoprecipitates were resolved by 8% SDS-PAGE and analyzed by immunoblotting with anti-pRb Mh-Rb-02P mAb (lanes 1-3), anti-hsc73 3a3 mAb (lane 5), anti-m65hsp B97 mAb (lane 6), and anti-hsp90 AC88 mAb (lane 7), respectively. Lane 4 shows hsc73 alone without pRb. Lanes 8-10 contain approximately 1 µg of purified hsc73, m65hsp, and hsp90 protein alone for positive controls of protein and mAbs, respectively. The bands were detected by developing for 30 s with ECL detection reagents.

Mapping of the hsc73 Binding Site in pRb

Figure 4: Hsc73 binds to a region N-terminal to the A-pocket in pRb. Panel A, recombinant proteins of five deletion mutants of pRb run on 8% SDS-PAGE and detected with anti-pRb mAbs reacting to the epitopes in amino acids 1-240 (mAb G99-2005) (lane 2), 300-380 (mAb Mh-Rb-02P) (lanes 1, 3, 4, and 5), and 514-610 (mAb G99-549) (lanes 6 and 7), respectively. The bands were detected by developing for 30 s with ECL detection reagents. Panel B, the excess amount (approximately 1-2 µg) of hsc73 was incubated with about 1 µg of either GST (lane 2), GST-del Rb301-514 (lane 3), GST-del Rb1-300 (lane 4), GST-del Rb1-514 (lane 5), GST-del Rb1-602 (lane 6), or GST-del Rb373-928 (lane 7) and precipitated by glutathione-Sepharose beads. Proteins were resolved by 8% SDS-PAGE and analyzed by immunoblotting with anti-hsc73 3a3 mAb. Lane 1 shows hsc73 alone containing 1 µg of protein for a positive control of mAb. The bands were detected by developing for 15 s with ECL detection reagents. Panel C, summary of GST-pRb deletion constructs and the ability of each pRb deletion mutant protein to bind to hsc73. A and B indicate the so-called A (residues 373-579) and B pockets (residues 640-771) of pRb, respectively.

These GST-del Rb mutant proteins were incubated with an excess amount of hsc73, followed by precipitation using glutathione-Sepharose beads. The precipitates were run on 8% SDS-PAGE and analyzed by immunoblotting with anti-hsc73 mAb. As shown in Fig. 4B, hsc73 was not detected in the precipitates of GST-del Rb1-300 and GST-del Rb373-928 (lanes 4 and 7, respectively), whereas it could be detected in the precipitates of GST-del Rb301-514, GST-del Rb1-514, and GST-del Rb1-602 (lanes 3, 5, and 6, respectively). These data suggest that hsc73 may interact with a region containing the N-terminal nonpocket region of 72 amino acids (residues 301-372) adjacent to the N-terminal boundary of the A pocket in pRb as summarized in Fig. 4C.

The possibility of hsc73 binding to the pocket regions was excluded by way of a competition experiment. Viral oncoprotein E1A is known to bind to so-called A/B pockets of pRb (Fig. 4C)(3, 4) . We tested whether purified E1A protein could compete with hsc73 for binding to pRb in vitro. pRb was immunoprecipitated from the mixture of equal molar amounts of purified hsc73 and purified pRb in the presence or absence of the same molar amounts of purified E1A protein, then subjected to SDS-PAGE and analyzed by immunoblotting with anti-hsc73 mAb. As shown in Fig. 5, pRb could form a complex with hsc73 independent of the presence of E1A protein. The amount of hsc73 coprecipitated with pRb did not differ between the absence (Fig. 5, lane 1) and presence (lane 2) of E1A. Furthermore, the amount of E1A protein coprecipitated with pRb did not differ between the presence (lane 4) and absence (lane 5) of hsc73. These data indicate that hsc73 can associate with pRb in a region distinct from the E1A binding region, suggesting the interaction of hsc73 with the nonpocket region of pRb.

Figure 5: Competition experiment of hsc73 with E1A for binding to pRb. Purified hsc73 (2 µg) and pRb (3 µg) were incubated with purified E1A (2 µg) (lane 2) or without E1A (lane 1). E1A and pRb were also incubated with hsc73 (lane 4) or without hsc73 (lane 5) at an equal molar ratio. All samples were precipitated by anti-pRb Mh-Rb-02P mAb, run on 8% SDS-PAGE, and analyzed by immunoblotting with anti-hsc73 3a3 mAb (lanes 1-3) or anti-E1A M73 mAb (lanes 4-6). Lanes 3 and 6 are the controls for hsc73 plus E1A without pRb. The bands were detected by developing for 30 s with ECL detection reagents.

Hsc73 Can Interact with Nonphosphorylated pRb but Not with Phosphorylated pRb in Vitro and in Vivo

Figure 6: Selective binding of hsc73 to non- or hypophosphorylated pRb. Panel A, purified pRb (1 µg) or hsc73 (1 µg) was incubated with (lanes 2 and 4) or without (lanes 1 and 3) 30 ng of cyclin-p34cdc2 complex at 25 °C for 30 min containing 0.1 mM cold ATP and 10-30 µCi of [P]ATP. Phosphorylated pRb was visualized by autoradiography of P. Panel B, hyperphosphorylated pRb (3 µg) (lanes 1, 4, and 7) and non- or hypophosphorylated pRb (3 µg) (lanes 2, 3, 5, 6, 8, and 9) were incubated with purified hsc73 (2 µg) and E1A (2 µg) and immunoprecipitated by anti-pRb Mh-Rb-02P mAb. The immunoprecipitates were resolved by 8% SDS-PAGE and analyzed by immunoblotting with anti-pRb Mh-Rb-02P mAb (lanes 1-3), anti-hsc73 3a3 mAb (lanes 4-6), and anti-E1A M73 mAb (lanes 7-9). The bands were detected by developing for 30 s with ECL detection reagents.

We further confirmed that hsc73 could associate preferentially in vivo with the nonphosphorylated and hypophosphorylated form of pRb. Since it was shown previously that okadaic acid treatment could phosphorylate pRb in vivo(25) , we treated HOS cells with this agent and obtained the phosphorylated from of pRb (Fig. 7, lane 1). In contrast, HOS cells without okadaic acid treatment showed a rather broad band corresponding to phosphorylated and nonphosphorylated pRb (lane 2). Then we made the immunoprecipitates with 3a3 mAb and HOS cell lysates, and the immunoprecipitates were Western blotted and analyzed by Mh-Rb-02P mAb. As shown in Fig. 7, lane 3, it appeared that hsc73 could associate preferentially only with nonphosphorylated or hypophosphorylated pRb.

Figure 7: In vivo physical association of nonphosphorylated pRb with hsc73. The lysates of HOS cells were immunoprecipitated with (lane 3) or without (lane 4) anti-hsc73 3a3 mAb, and these immunoprecipitates were immunoblotted. The lysate alone of HOS cells with 100 nM okadaic acid treatment for 2 h (lane 1) or without treatment (lane 2) was also employed. The mixture of 50 µl of cell lysate alone and 50 µl of SDS sample buffer was run on 8% SDS-PAGE and immunoblotted. These blots were subsequently detected by anti-Rb Mh-Rb-02P mAb as described above. The bands were detected by developing for 30 s with ECL detection reagents. ppRb and pRb indicate a mobility in SDS-PAGE of the phosphorylated and nonphosphorylated forms of pRb, respectively.

These in vitro and in vivo data indicate that hsc73 can interact with the nonphosphorylated or hypophosphorylated form but not with hyperphosphorylated form of pRb, suggesting that there might be a regulatory mechanism of the molecular interaction similar to that of other pRb-binding proteins such as viral oncoproteins and transcription factors. It is speculated that hsc73 may dissociate from the pRb complex following pRb phosphorylation by cyclin/cyclin-dependent kinases during cell cycle progression.

DISCUSSION

pRb plays an important role in regulating the cell cycle by interacting with some nuclear proteins. The regions of pRb mediating protein interactions have been identified. The region in pRb which mediates the interaction with transcriptional factor E2F is located in the C-terminal region containing regions referred to as A/B pockets (residues 373-771) (7) and is necessary in the growth-suppressive function of pRb(8, 9) . Several viral oncoproteins can bind to the pocket region and block the binding of pRb to E2F, resulting in an uncontrolled transcriptional activation and cellular transformation. Nuclear c-Abl tyrosine kinase was also shown to interact with pRb(15) . Unlike viral oncoproteins, the c-Abl binding region of pRb has been mapped to the C-terminal region downstream from the pockets. In this complex, pRb appeared to regulate the kinase activity of c-Abl during the cell cycle.

We have reported previously that one of the 70-kDa heat shock protein families, hsc73, could interact with pRb in vivo(16) . Our present data showed that hsc73 could interact directly with pRb in vitro and that the interaction was specific since neither hsp90 nor m65hsp could associate with pRb. The mapping of the hsc73 binding site of pRb revealed a novel region within the N-terminal region upstream from the pockets. The binding of hsc73 to pRb was unaffected by the viral oncoprotein E1A, suggesting that there might be a different biological role for this interaction.

Protein interactions depend on the unique amino acid motif to interact with each other specifically. BiP, the sole member of the hsp70 families localized in the endoplasmic reticulum of eukaryotic cell, is known to recognize polypeptides that contain a heptameric motif best described as HyXHyXHyXHy, where Hy is a large hydrophobic amino acid and X is any amino acid(27) . The N-terminal 301-372 amino acid residues outside the A/B pocket of pRb contain this heptameric motif (residues 331-337). Since the substrate binding domains of BiP and hsc73 are suggested to have the identical structure, it can be speculated that hsc73 binds to pRb by recognizing this motif.

We need to consider one other possible explanation for deletion mutant binding studies. Members of the hsp70 family appear capable of recognizing ``nonnative'' form of proteins(28) . Consequently one could argue that the differential binding observed in this study simply represents mutants that have folded either into a native or nonnative-like configuration. Indeed this is a problem that will always have to be considered regarding proteins that bind stably to members of the molecular chaperone family. However, in this present study we showed that all deletion mutants that contain pRb301-372 could bind to hsc73, whereas no deletion mutants lacking this region could bind to hsc73. It is highly unlikely that all mutant proteins that contain pRb301-372 become nonnative or malfolded proteins and consequently bind to hsc73 and vice versa. Therefore, our present studies strongly indicate that the primary pRb 301-372 sequence is important for binding to hsc73.

Meanwhile, we also have to mention the stoichiometry or affinity of the pRb and hsc73 interaction. One of the key observations is presented in Fig. 4B on the interaction between hsc73 and a specific region of pRb. In these experiments, 1 µg of the various GST-del Rb constructs is incubated with 1-2 µg of hsc73 and the complexes detected by immunoprecipitation and Western blot analysis. Lane 1 of Fig. 4B corresponds to the input amount of hsc73, therefore comparison with the other lanes gives some indication of the stoichiometry or affinity of pRb and hsc73 interaction. It is indicated that some of the bands are very weak (lane 6). This could be interpreted that the interaction is either of low affinity, that the GST-del Rb proteins are heterogeneous resulting in reduced stoichiometry, or that it is a malfolded subpopulation of the GST-del Rb proteins which interacts with hsc73. Further experiments are required to clarify each of these possibilities.

It is known that hsp families act as molecular chaperones(29, 30) . Hsp70 families can associate physically with various intracellular proteins and work for the regulation of conformational changes, translocation, and stabilization of these proteins. Although the functional significance of hsp70 families for cell growth or malignant transformation has not been clarified yet, it has been reported that overexpression of hsc73 could suppress oncogene-mediated transformation (31) . Therefore it is speculated that hsc73 can function as a tumor suppressor in the process of transformation and that this function may be mediated by the pRb through their physical association. Hsc73 may change the conformation of pRb so that pRb becomes resistant to phosphorylation since phosphorylation of pRb results in the dissociation of the pRb-E2F complex and the loss of the growth-suppressive effect. We tested the susceptibility of pRb to phosphorylation in vitro by p34cdc2 kinase in the presence of hsc73. However, there was no change in the pRb phosphorylation (data not shown). It is noteworthy that another tumor suppressor, p53, is also associated with hsc73 (32, 33, 34, 35) and that the interaction is mediated by the N-terminal region of p53(36) . Therefore, it is speculated alternatively that hsc73 may stabilize the nonphosphorylated or the hypophosphorylated pRb and extend its half-life in a manner analogous to that of mutant p53.

None of the pRb-binding proteins has been shown to bind to hyperphosphorylated pRb so far. Unexceptionally, hsc73 could not interact with the hyperphosphorylated form of pRb, suggesting a regulatory mechanism of the hsc73-pRb interaction similar to that of other pRb-binding proteins. It has been shown that pRb can be phosphorylated at several serine or threonine residues in various regions. The hsc73 binding region also includes at least two threonine residues, which could become a substrate for cyclin-dependent kinase(37, 38, 39, 40) , indicating that the dissociation might depend on the direct phosphorylation of the binding region rather than on the conformational change following phosphorylation of other regions. Interestingly, the hsc73-pRb complex could be disrupted by the addition of a high concentration of ATP. ADP could not induce the disruption efficiently, suggesting that the dissociation might be mediated by ATP hydrolysis by hsc73. However, as shown in Fig. 2, lane 5, we noted that the addition of the nonhydrolyzable ATP analog ATPs did in fact result in considerable dissociation of the complex. This may be consistent with work by Palleros et al.(41) , suggesting that it is ATP exchange rather than ATP hydrolysis.

Finally, two important questions remain to be answered. What is the biological significance of the formation of the hsc73-pRb complex? What is the functional significance of the ATP-dependent disruption of the complex in the cell cycle? Gene transfer experiments using mutant hsc73 or mutant pRb may help to resolve some of these questions.

FOOTNOTES

*

This work was supported by a grant-in-aid for scientific research from the Ministry of Education, Culture, and Science of Japan. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked ``advertisement'' in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

§

To whom correspondence should be addressed: Dept. of Pathology, Sapporo Medical University School of Medicine, South 1, West 17, Chuo-ku, 060 Sapporo, Japan.

()

The abbreviations used are: hsc73, 73-kDa heat shock cognate protein; m65hsp, mycobacterial 65-kDa heat shock protein; hsp90, human 90-kDa heat shock protein; mAb(s), monoclonal antibody(ies); DTT, dithiothreitol; GST, glutathione S-transferase; CHAPS, 3-[(cholamidopropyl)dimethylammonio]-1-propanesulfonic acid; PAGE, polyacrylamide gel electrophoresis; ATPS, adenosine 5`-3-O-(thio)triphosphate.

()

Saijo, M., Sakai, Y., Kishino, T., Niikawa, N., Matsuura, Y., Morino, K., Tamai, K., and Taya, Y.(1995) Genomics27, 511-519.

ACKNOWLEDGEMENTS

REFERENCES

1. Weinberg, R. A. (1992) Cancer Surv. 12,43-57 [Medline] [Order article via Infotrieve]
2. Helin, K., and Harlow, E. (1993) Trends Cell Biol. 3,43-46
3. Hu, Q., Dyson, N., and Harlow, E. (1990) EMBO J. 9,1147-1155 [Medline] [Order article via Infotrieve]
4. Kaelin, W. G., Jr., Ewen, M. E., and Livingston, D. M. (1990) Mol. Cell. Biol. 10,3761-3769 [Abstract/Free Full Text]
5. Kaelin, W. G., Jr., Pallas, D. C., DeCaprio, J. A., Kaye, F. J., and Livingston, D. M. (1991) Cell 64,521-532 [CrossRef][Medline] [Order article via Infotrieve]
6. Bandara, L. R., and La Thangue, N. B. (1991) Nature 351,494-497 [CrossRef][Medline] [Order article via Infotrieve]
7. Chellappan, S. P., Hiebert, S., Mudryj, M., Horowitz, J. M., and Nevins, J. R. (1991) Cell 65,1053-1061 [CrossRef][Medline] [Order article via Infotrieve]
8. Nevins, J. R. (1992) Science 258,424-429 [Abstract/Free Full Text]
9. Hiebert, S. W. (1993) Mol. Cell. Biol. 13,3384-3391 [Abstract/Free Full Text]
10. Reed, S. I. (1992) Annu. Rev. Cell Biol. 8,529-561 [CrossRef]
11. Sherr, C. J. (1993) Cell 73,1059-1065 [Medline] [Order article via Infotrieve]
12. Huang, S., Wang, N.-P., Tseng, B. Y., Lee, W.-H., and Lee, E. H.-H. P. (1990) EMBO J. 9,1815-1822 [Medline] [Order article via Infotrieve]
13. Ewen, M. E., Sluss, H. K., Sherr, C. J., Matsushime, H., Kato, J., and Livingston, D. M. (1993) Cell 73,487-497 [CrossRef][Medline] [Order article via Infotrieve]
14. Shew, J.-Y., Lin, B. T.-Y., Chen, P.-L., Tseng, B. Y., Yang-Feng, T. L., and Lee W.-H. (1990) Proc. Natl. Acad. Sci. U. S. A. 87,6-10 [Abstract/Free Full Text]
15. Welch, J. W., and Wang, J. Y. (1993) Cell 75,779-790 [CrossRef][Medline] [Order article via Infotrieve]
16. Nihei, T., Takahashi, S., Sagae, S., Sato, N., and Kikuchi, K. (1993) Cancer Res. 53,1702-1705 [Abstract/Free Full Text]
17. Matsuura, Y., Possee, R. D., Overton, H. A., and Bishop, D. H. L. (1987) J. Gen. Virol. 68,1233-1250 [Abstract/Free Full Text]
18. Guan, K.-L., and Dixon, I. E. (1991) Anal. Biochem. 192,262-267 [CrossRef][Medline] [Order article via Infotrieve]
19. Hara, I., Sato, N., Matsuura, A., Cho, J.-M., Weimin, Q., Torigoe, T., Shinnick, T. M., Kamidono, S., and Kikuchi, K. (1991) Microbiol. Immunol. 35,995-1007 [Medline] [Order article via Infotrieve]
20. Cance, W., Brennan, M. F., Ducas, M. E., Huang, C. M., and Cordon-Cardo, C. (1990) N. Engl. J. Med. 323,1457-1462 [Abstract]
21. Weinberg, R. A. (1991) Science 254,1138-1146 [Abstract/Free Full Text]
22. Cho, J. M., Sato, N., Yagihashi, A., Konno, A., Hara, I., Konn, S., Torigol, T., Qir, W., Takashima, T., Takahashi, N., and Kikuchi, K. (1991) Cancer Res. 51,4250-4256 [Abstract/Free Full Text]
23. Smith, D. B., Davern, K. M., Board, P. G., Tiu, W. U., Garcia, E. G., and Mitchell, G. F. (1986) Proc. Natl. Acad. Sci. U. S. A. 83,8703-8707 [Abstract/Free Full Text]
24. Smith, D. B., and Johnson, K. S. (1988) Gene (Amst.) 67,31-40 [CrossRef][Medline] [Order article via Infotrieve]
25. Yatsunami, J., Komori, A., Ohta, T., Suganuma, M., and Fujiki, H. (1993) Cancer Res. 53,239-241 [Abstract/Free Full Text]
26. Brown, C. R., Martin, R. L., Hansen, W. J., Beckmann, R. P., and Welch, W. J. (1993) J. Cell Biol. 120,1101-1112 [Abstract/Free Full Text]
27. Blond-Elguindi, S., Cwirla, S. E., Dower, W. J., Lipshutz, R. J., Sprang, S. R., Sambrook, J. F., and Gething, M.-J. H. (1993) Cell 75,717-728 [CrossRef][Medline] [Order article via Infotrieve]
28. Palleros, D. R., Welch, W. J., and Fink, A. L. (1991) Proc. Natl. Acad. Sci. U. S. A. 88,5719-5723 [Abstract/Free Full Text]
29. White, E., Spector, D., and Welch, W. (1988) J. Virol. 62,4153-4166 [Abstract/Free Full Text]
30. Beckmann, R. P., Mizzen, L. A., and Welch, W. J. (1990) Science 248,850-854 [Abstract/Free Full Text]
31. Yehiely, F., and Oren, M. (1992) Cell Growth & Differ. 3,803-809
32. Pinhasi-Kimhi, O., Michalovitz, D., Bin-Zeev, A., and Oren, M (1986) Nature 320,182-185 [CrossRef][Medline] [Order article via Infotrieve]
33. Hinds, P. W., Finlay, C. A., Frey, A. B., and Levine, A. J. (1987) Mol. Cell. Biol. 7,2863-2869 [Abstract/Free Full Text]
34. Finlay, C. A., Hinds, P. W., Tan, T.-H., Eliyahu, D., Oren, M., and Levine, A. J. (1988) Mol. Cell. Biol. 8,531-539 [Abstract/Free Full Text]
35. Lehman, T. A., Bennett, W. P., Metcalf, R. A., Welsh, J. A., Ecker, J., Modali, R. V., Ullrich, S., Romano, J. W., Appella, E., Testa, J. R., Gerwin, B. I., and Harris, C. C. (1991) Cancer Res. 51,4090-4096 [Abstract/Free Full Text]
36. Lam, K. T., and Calderwood, S. K. (1992) Biochem. Biophys. Res. Commun. 184,167-174 [CrossRef][Medline] [Order article via Infotrieve]
37. Taya, Y., Yasuda, H., Kamijo, M., Nakaya, K., Nakamura, Y., Ohba, Y., and Nishimura, S. (1989) Biochem. Biophys. Res. Commun. 164,580-586 [CrossRef][Medline] [Order article via Infotrieve]
38. Taya, Y., Yasuda, H., Kamijo, M., Nakaya, K., Nakamura, Y., Ohba, Y., and Nishimura, S. (1990) Genetic Basis for Carcinogenesis, Knudson, A. G., Jr., Stanbridge, E. J., Sugumura, T., Terada, M., and Watanabe, S. (eds) Taylor & Francis Ltd., London, pp. 171-176
39. Lees, J. A., Buchkovich, K. J., Marshak, D. R., Anderson, C. W., and Harlow, E. (1991) EMBO J. 10,4279-4290 [Medline] [Order article via Infotrieve]
40. Lin, B. T.-Y. Gruenwald, S., Morla, A. O., Lee, W.-H., and Wang, J. Y. J. (1991) EMBO J. 10,857-864 [Medline] [Order article via Infotrieve]
41. Palleros, D. R., Reid, K. L., Shi, L., Welch, W. L., and Fink, A. L. (1993) Nature 365,664-666 [CrossRef][Medline] [Order article via Infotrieve]

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