Estrogen Receptor Of The Adjustment Factor RSRC1 Biological Function Study

Breast cancer is one of the most common forms of cancer observed in women. Endogenous estrogen is thought to play an important role in breast cancer development.Accumulated evidence indicates that ER is involved in proliferation of breast cancer cells and is implicated in the development and progression of breast cancer.Regulation of gene expression by the ERs requires cofactor interactions.Most of the identified cofactors are co-activators.There have been some cofactors shared between ERα.and ERβ.Since ERβwas discovered more recently,very few cofactors for ERβhave been reported.Moreover,the intracellular signaling pathways modulating ER transcriptional activity are not fully elucidated.To investigate the role of ERβin estrogen signaling pathway and search for new transcriptional co-regulators,we screend a human mammary cDNA library using the ERβAF-2 domain as bait in the two-hybrid system.Several positive clones were identified to interact with ERβ,one of which was RSRC1(arginine/serine-rich coiled-coil 1),the protein we know nothing about previously.We generated RSRC1 antibodies against a peptide from aa 180 to 224 of the RSRC1 protein,which covers the coiled coil structure(SR domain),and can participate in the protein-protein interactions.Western blot analysis showed that there were 4 bands with apparent molecular mass of 25kDa,40kDa,45kDa and 53kDa when we used the antibodies to detect the RSRC1 protein.So we confirm that all of these 4 bands were RSRC1 with different modified formation.RSRC1 expression was observed in most breast cancer cells.To investigate the localiztion of RSRC1 and ER,GFP labeled RSRC1 was co-transfected with RFP labeled ERαor ERβin ZR75-1 cells.RSRC1 was localized to the nuclear speckled domain.In 293T cells and ZR-75-1 cells,the transcriptional activity of ERαand ERβwere increased by RSRC1 over-expression in E2-indepented and dose-depended manner. The effect of over-expressed RSRC1 on growth of ZR75-1 cells was examined.In the presence or absence of estrogen,the cell with transient transfection of Flag-RSRC1 showed a reduced rate of proliferation rate in comparison with the control.The effect of RSRC1 on the expression of endogenous ERαtarget genes was examined. Transient transfected RSRC1 decressed expression of most ER target genes,such as PR,C3,pS2 and C-fos;however,CyclinD1 was enhanced as expected.In addition, Cat-D and C-myc did not change much.Since RSRC1 interact with ERαand ERβand increases the transcriptional activity of them,RSRC1 may be a co-factor of ERs.More insight into RSRC1 would be helpful for the ER pathway understanding and clinic application.