Novel role of the RET finger protein in estrogen receptor-mediated transcription in MCF-7 cells.
The Scaffold attachment factor B1 (SAFB1) is an estrogen receptor (ESR1) repressor that has been proposed to inhibit breast tumorigenesis. To obtain insight into the functions of SAFB1 we utilized a yeast two-hybrid screen and identified the Ret finger protein (RFP) as interacting with the SAFB1 C-terminus. RFP is a member of the trimotif (TRIM) family of proteins, which we found widely expressed in a series of breast cancer cell lines. We confirmed the interaction between SAFB1 and RFP through in vitro (GST-pull-down) and in vivo (coimmunoprecipitations) assays. We hypothesized that SAFB1 functions as a scaffolding protein to recruit proteins such as RFP into proximity with ESR1. Consequently, we asked whether RFP would modulate ESR1 activity and we discovered that RFP was important for the ESR1-dependent expression of cyclin D1 (CCND1) and the progesterone receptor (PR), but not IRS1 or MYC. Although RFP did not interact with ESR1 directly, it does coimmunoprecipitate with ESR1, demonstrating that RFP is found within the same protein complex. Chromatin immunoprecipitation assays (ChIP) located RFP to the TFF1 promoter, a known ESR1-regulated gene. Taken together, our study provides further evidence that coactivation and corepression are integrally linked processes and that RFP is a component of an ESR1 regulatory complex.
Townson
Steven M
SM
Department of Human Genetics, Virginia Commonwealth University and Massey Cancer Center, Sanger Hall, Richmond, VA 23219, USA. smtownson@mail1.vcu.edu
Kang
Kaiyan
K
Lee
Adrian V
AV
Oesterreich
Steffi
S
D000818:Animals; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D019938:Cyclin D1 / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism; D014158:Transcription, Genetic; D000070584:Tripartite Motif Proteins
D019938:Cyclin D1; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C064419:TRIM27 protein, human; D000070584:Tripartite Motif Proteins