Breast Cancer Metastasis Suppressor 1 (BRMS1) Forms Complexes with Retinoblastoma-binding Protein 1 (RBP1) and the mSin3 Histone Deacetylase Complex and Represses Transcription

Abstract

Breast cancer metastasis suppressor 1 (BRMS1) suppresses metastasis of multiple human and murine cancer cells without inhibiting tumorigenicity. By yeast two-hybrid and co-immunoprecipitation, BRMS1 interacts with retinoblastoma binding protein 1 and at least seven members of the mSin3 histone deacetylase (HDAC) complex in human breast and melanoma cell lines. BRMS1 co-immunoprecipitates enzymatically active HDAC proteins and represses transcription when recruited to a Gal4 promoter in vivo. BRMS1 exists in large mSin3 complex(es) of ϳ1.4 -1.9 MDa, but also forms smaller complexes with HDAC1. Deletion analyses show that the carboxyl-terminal 42 amino acids of BRMS1 are not critical for interaction with much of the mSin3 complex and that BRMS1 appears to have more than one binding point to the complex. These results further show that BRMS1 may participate in transcriptional regulation via interaction with the mSin3⅐HDAC complex and suggest a novel mechanism by which BRMS1 might suppress cancer metastasis.The complex process of cancer cell dissemination and the establishment of secondary foci involves the acquisition of multiple abilities by metastatic cells. For example, blood-borne metastasis requires cells to invade from the primary tumor, enter the circulation, survive transport, arrest at a secondary site, recruit a blood supply, and proliferate at that site (1). The ability to accomplish all of these steps likely involves changes in, and coordinated expression of, a large assortment of genes. Consistent with this notion, several genes, proteins, and pathways have been associated with metastatic progression, including oncogenes, motility factors, and matrix metalloproteinases (1, 2). In addition to metastasis-promoting genes, a new class of molecules called metastasis suppressors has been described (reviewed in Refs. 2-5). By definition, metastasis suppressors inhibit metastasis without blocking primary tumor growth, presumably by inhibiting one or more steps necessary for metastasis. To date, 13 metastasis suppressor genes have been identified that reduce the metastatic ability of cancer cell line(s) in vivo without affecting tumorigenicity, namely breast cancer metastasis suppressor 1 (BRMS1), 1 CRSP3, DRG1, KAI1, KISS1, MKK4, NM23, RhoGDI2, RKIP, SSeCKs, VDUP1, E-cadherin, and TIMPs (reviewed in Refs. 4 and 5).We identified BRMS1 using differential display to compare highly metastatic breast carcinoma cells with related but metastasis-suppressed cells (6). Enforced expression of BRMS1 suppressed metastasis in three animal models, namely human breast (6), murine mammary (7), and human melanoma cells (8). Additionally, BRMS1 mapped to loci in murine (7) and human (6) genomes that had previously been implicated in metastasis control (9). The BRMS1 protein localized to nuclei and restored gap junctional intercellular communication in both breast and melanoma tumor cell lines (8,10,11), but its molecular functions remain to be elucidated.One approach to determine a mechanism of action involves identifying which...

The MYST family of histone acetyltransferases and their intimate links to cancer

“…ING3, -4 and -5 are found in complexes with MYST HATs as described above (Doyon et al, 2004(Doyon et al, , 2006, whereas ING1 and -2 stably associate with two very similar mSin3 histone deacetylase (HDAC) complexes (Skowyra et al, 2001;Kuzmichev et al, 2002;Doyon et al, 2006). Notably, the mSin3 complex also contains subunits RBP1 (Rb-binding protein 1) (Lai et al, 2001) and BRMS1 (breast cancer metastasis suppressor) (Meehan et al, 2004). RBP1 facilitates recruitment of this complex by the pocket proteins of the Rb family, which utilize the associated HDAC activity to suppress transcription from E2F-responsive promoters and to shut down DNA replication origins, leading to cell-cycle arrest (Lai et al, 2001).…”

Epigenetic silencing contributes to the loss of BRMS1 expression in breast cancer

“…BRMS1 has also been reported to suppress NFκ-B signaling through blockage of IκBα [11][12][13]. Further, BRMS1 gene regulatory mechanisms have been shown to involve histone deacetylases [14,15]. Proteomic as well as genomic analysis strategies have been used to reveal downstream targets of BRMS1 [16][17][18].…”

mSin3A corepressor regulates diverse transcriptional networks governing normal and neoplastic growth and survival

“…The maintenance of mSin3-associated HDAC activity is dependent on another integral component, mSds3, whose ortholog in Saccharomycese cerevisiae is epistatic to the yeast sin3p and HDAC orthologs (Vannier et al 1996;Alland et al 2002). Additional core mSin3/HDAC proteins include the retinoblastoma-associated proteins, RbAp46 and RbAp48, which are thought to stabilize interactions with the mSin3 complex and the nucleosome, mSin3-associated proteins (SAPs: SAP18, SAP30, SAP130, and SAP180), RBP1, p33ING1b, and BRMS1, which have been isolated through biochemical means and remain the focus of ongoing functional investigations (for review, see Ayer 1999;Kuzmichev et al 2002;Lai et al 2001;Skowyra et al 2001;Fleischer et al 2003;Meehan et al 2004).…”