Prohibitin requires Brg-1 and Brm for the repression of E2F and cell growth

Abstract

E2F transcription factors play a major role in controlling mammalian cell cycle progression. We recently reported that a potential tumor suppressor, prohibitin, which interacts with retinoblastoma protein (Rb), regulates E2F function and this activity correlates with its growth-suppressive activity. We show here that prohibitin recruits Brg-1/Brm to E2F-responsive promoters, and that this recruitment is required for the repression of E2F-mediated transcription by prohibitin. Expression of a dominantnegative Brg-1 or Brm releases prohibitin-mediated repression of E2F and relieves prohibitin-mediated growth suppression. Although prohibitin associates with, and recruits, Brg-1 and Brm independently of Rb, prohibitin/Brg-1/Brm-mediated transcriptional repression requires Rb. A viral oncoprotein, SV40 large T antigen, can reverse prohibitin-mediated suppression of E2F-mediated gene transcription, and targets prohibitin through interruption of the association between prohibitin and Brg-1/Brm without affecting the prohibitin±E2F interaction. Keywords: Brg-1/Brm/E2F/prohibitin/SV40 T antigen IntroductionProhibitin is a potential tumor suppressor gene that has been linked to human cancers. The prohibitin gene encodes a protein of 275 amino acids that is highly evolutionarily conserved. The prohibitin gene is located at 17q21, close to the BRCA1 locus, and four mutations have been reported in a screen of 23 sporadic breast cancers, suggesting a role for prohibitin in breast cancer (Sato et al., 1992(Sato et al., , 1993. The prohibitin gene was originally cloned based on its anti-proliferative activity, causing cell cycle arrest at G 1 /S (McClung et al., 1992(McClung et al., , 1995Asamoto and Cohen, 1994;Ikonen et al., 1995;Dell'Orco et al., 1996;Coates et al., 1997). We recently reported that prohibitin physically interacts with E2F and regulates E2F function, and that this interaction is necessary for the growth-suppressive activity of prohibitin (Wang et al., 1999a,b).The E2F family of transcription factors plays a major role in regulating mammalian cell cycle progression and is involved in differentiation, transformation and apoptosis (Chellappan et al., 1991;Nevins, 1992Nevins, , 1998 Kaelin, 1995, 1996;Harbour and Dean, 2000;Muller and Helin, 2000). Many cellular genes required for progression through the S phase contain E2F-binding sites in their promoters, and E2F activity is essential for their expression (Adams and Kaelin, 1995). It has been established that the retinoblastoma protein (Rb) family of tumor suppressors interacts with E2F and regulates their function (Chellappan et al., 1991). Recent studies have shown that Rb represses E2F-mediated transcriptional activation through recruitment of chromatin-remodeling complexes, such as histone deacetylase (HDAC) and Brg-1/Brm (Dunaief et al., 1994;Brehm et al., 1998;.We have found that prohibitin interacts with all members of the Rb family (Wang et al., 1999a) and demonstrated important functional and mechanistic differences between Rb-and prohibitin-mediated ...

Prohibitin interacts with RNF2 and regulates E2F1 function via dual pathways

“…Using anti-prohibitin antibodies, we initially immunoprecipitated chromatin from HEK293 cells and performed ChIP PCR with E2F1, TK and p107 primers, which were previously reported to be prohibitin-recruiting promoters (Wang et al, 2002). As expected, prohibitin was recruited to the promoters Interaction between prohibitin and RNF2 D Choi et al tested (Figure 7d, left panel).…”

“…Prohibitin represses the transcriptional activity of E2Fs1-5 by recruiting co-repressors, including histone deacetylase 1, N-CoR and BrG1/ Brm (Wang et al, 2002), whereas Rb represses the transcriptional activity of E2Fs1-3 by recruiting histone deacetylase 1, DNA methyltransferase and BrG1/Brm (Luo et al, 1998;Magnaghi-Jaulin et al, 1998;Zhu, 2005). Prohibitin and Rb interact with distinct regions of E2F1 and respond to different upstream signals (Wang et al, 1999b).…”

Androgens target prohibitin to regulate proliferation of prostate cancer cells

“…Injection of the mRNA results in cell-cycle arrest in some cell types (McClung et al, 1989;Nuell et al, 1991), and this may in part be due to the 3 0 untranslated region (3 0 UTR) of the mRNA (Jupe et al, 1996). Even the localization of the protein is not clear, with some groups maintaining that the protein is purely mitochondrial (Coates et al, 2001), and others demonstrating a secondary localization in the nucleus (Thompson et al, 2001;Wang et al, 2002b). However, recent observations that prohibitin can interact with members of the E2F transcription factor family (Wang et al, 1999a) support the concept of a nuclear role in cell-cycle regulation.…”

320 Prohibitin 1 Modulates Mitochondrial Stress-Related Autophagy in Human Colonic Epithelial Cells

“…One potential mechanism whereby PHB regulates beclin-1, the first mammalian gene shown to induce autophagy, is through the transcription factor E2F1. The beclin-1 promoter contains a putative E2F1 binding site [57] and PHB has been shown to regulate E2F1 activity [35]. Future studies will investigate this possibility.…”

“…Prohibitin 1 (PHB) is an evolutionarily conserved, multifunctional 32 kDa protein implicated in cellular processes including the regulation of proliferation, apoptosis, and transcription [33,34,35,36]. PHB is predominantly localized to the mitochondria in intestinal epithelial cells [37] and multiple studies have shown that PHB plays a role in maintaining normal mitochondrial function and morphology (reviewed in [38]).…”