RBP1 Recruits Both Histone Deacetylase-Dependent and -Independent Repression Activities to Retinoblastoma Family Proteins

Abstract

Retinoblastoma (RB) tumor suppressor family proteins block cell proliferation in part by repressing certain E2F-specific promoters. Both histone deacetylase (HDAC)-dependent and -independent repression activities are associated with the RB "pocket." The mechanism by which these two repression functions occupy the pocket is unknown. A known RB-binding protein, RBP1, was previously found by our group to be an active corepressor which, if overexpressed, represses E2F-mediated transcription via its association with the pocket. We show here that RBP1 contains two repression domains, one of which binds all three known HDACs and represses them in an HDAC-dependent manner while the other domain functions independently of the HDACs. Thus, RB family members repress transcription by recruiting RBP1 to the pocket. RBP1, in turn, serves as a bridging molecule to recruit HDACs and, in addition, provides a second HDAC-independent repression function.The retinoblastoma (RB) tumor suppressor protein pRB plays a critical role in the control of cell proliferation. In addition, loss of the Rb gene is known to contribute to the establishment of a variety of cancers. pRB and the related proteins p130 and p107 control cell cycle progression through interactions with the E2F family of transcription factors (reviewed in reference 11). Such interactions regulate transcription by mechanisms requiring the "pocket" domain of RB family members (1,3,5,18,32,39,40,46). One role of the pocket is to interact with and mask the transcriptional activation domain of E2F; however, this mechanism does not explain the repression of E2F-dependent promoters in which E2F binding sites act as negative elements that, if deleted, result in relief from repression (7,11,20,28). The pocket can interact simultaneously with both E2F and certain cellular and viral proteins that bind by utilizing a conserved Leu-X-Cys-X-Glu FIG. 1. Endogenous interactions of pRB (A) and p107 (B) with HDACs. (A) Immunoprecipitations were done in lysates from either H1299 or 293T cells. Plates (100 mm) of both cell types were lysed in low-stringency buffer. Cell extracts were incubated with 1 g of the indicated antisera and 30 l of a 50% slurry of protein G-Sepharose for at least 12 h. Immunoprecipitated complexes were washed six times with the 150 mM low-stringency buffer and eluted by boiling with 2ϫ sample buffer. Eluted proteins were subjected to SDS-PAGE with a 6% polyacrylamide gel. The presence of pRB was detected with monoclonal antibody (G3-245) against pRB (PharMingen). (B) Binding studies similar to those described for panel A were done, but coimmunoprecipitation of p107 was detected with a rabbit polyclonal antibody (C-18) against p107 (␣-107) (Santa Cruz).

Histone Deacetylases Augment Cytokine Induction of the iNOS Gene

“…Only a few transcription factors have been found to interact with HDAC without intermediate coregulatory molecules. Retinoblastoma protein interacts directly with HDAC1 (41), and SP1 also interacts with HDAC2 (42). YY1-induced transcriptional repression is the result of direct interaction with HDAC2 (43).…”

Ring-Sp1 decoy oligonucleotide effectively suppresses extracellular matrix gene expression and fibrosis of rat kidney induced by unilateral ureteral obstruction

“…14 Sp1 has been recognized as a basal factor required for activating the transcription of TATA-less promoters of cell cycle regulators including DHFR, thymidine kinase, and DNA polymerase. 15,16 Sp1 family members and E2F, another family of transcription factors, cooperatively activates transcription through physical interaction or a cis-acting mechanism, and regulate exit from and the progression of the cell cycle. [17][18][19][20] Specifically, pRb stimulates the transcription of c-myc and c-fos through the binding of Sp1 to their promoter elements.…”

Impact of nucleosome dynamics and histone modifications on cell proliferation during Arabidopsis development

“…In mammalian cells, the Rb protein interacts with HDAC either directly (Brehm et al, 1998;MagnaghiJaulin et al, 1998) or indirectly with the help of RbAp48/ MSI1 (Lai et al, 1999). These mechanisms contribute to recruit HDAC to E2F-bound promoters at early G1 and maintain their repressed state (Ferreira et al, 2001;Rayman et al, 2002).…”