Pes1 And The Interaction Of The Estrogen Receptor In Breast Cancer

Breast cancer,a kind of typical hormone-dependent tumor,is one of the common manlignant tumors jeopardizing womens' health.Estrogen(E₂)plays an important role in the development of breast cancer via estrogen receptor(ER)signaling pathway. This pathway is modulated by proteins called coregulators.It is greatly significant to discover and characterize the coregulators,which interact with ERs,in elucidating the development of breast cancer and finding new targets of the therapy or prognosis of breast cancer.There are two kinds of ER(ERαand ERβ,which are different each other in the tissue distribution,ligand affinity and transcriptional activity in spite of their high homology in the structure.ERs have four functional regions:transactivation regions AF1 and AF2,DNA binding domain(DBD)and hinge area.AF1 is a ligand-indepen dent transactivation region,however,AF2 has ligand-dependent transactivation function.ERs can regulate the E₂-responsive target gene expression via the synergistic effect of AF1 and AF2.The DBDs of ERαand ERβshare 96%of homology in the sequence and thus they can bind the same ERE sequence.However, the homology of AF1 and AF2 between ERαand ERβis only 30%and 50%, respectively.Pescadillo was originally identified in the research of embryonic development defect evoked by retrovirus in the zebrafish.Pescadillo is well conserved between species of human(PES1),yeast(YPH1,Nop7p),and mouse(Pes1).Analyses of the predicted amino acid sequence of PES1 identified the presence of a BRCA1 C-terminal(BRCT)-domain in amino acids 315-412.The BRCT domain has been found in several proteins involved in DNA repair and/or recombination,and cell cycle control.It has been shown by researchers that PES1 participates in cell cycle and is necessary for ribosome biogenesis and nucleologenesis and mutation or deficiency of PES1 results in cell cycle arrest.We found that PES1 could interact with ERαand ERβ.in vivo by coimmunprecipitation assay.E₂ could enhance the interaction of PES1 with ERαbut had no effect on the interaction of PES1 with ERα.The 1-160aa region of PES1 interacted with ERαand ERβ.Nevertheless,the AF2 of ERα.and AF1 of ERβinteracted with PES1.In breast cancer cell MCF-7,overexpression of PES1 could increase the transcriptional activity of ERαand decrease that of ERβby increasing the ERα protein expression level and decreasing the ERβ.protein expression level.In the stably PES1 siRNA-transfected MCF-7 cells,the transcriptional activity of ERα.decreased and the transcriptional activity of ERβ.increased accompanied by decreased ERαprotein expression and increased ERβ.protein expression.But the mRNA levels of ERαand ERβ.did not change significantly compared with the control,and E₂ has no effect on the mRNA levels.With the knockdown of PES1,p21 expression increased dominantly,pS2 and C3 protein decreased to an undetectable level.E₂ could increased the expression of pS2 and C3 in the control cells,but had no effect on the expression of p21 in the control cells and the stably PES1 siRNA-transfected MCF-7 cells.These results suggest that PES1 may regulate the expression of ERαand ERβat the post-translation level and knockdown of PES1 expression may selectively change the expression of ER downstream target genes.The growth velocity of the stably PES1 siRNA-transfected MCF-7 cells was significantly slower than that of the control cells, and cells were arrested in the G2 phage.The soft agar colony forming ability of stably PES1 siRNA-transfected MCF-7 cells decreased dominantly.In vivo,PES1 decreased the expression of ERβ.protein via increasing the ubiquitination of ERβand decreasing its sumoylation.Moreover,PES1 increased the ERαprotein level with increasing its sumoyaltion and decreasing its ubiquitination. E₂ could degrade the PES1 protein and attenuated the effects of PES1 on sumoylation and ubiquitination of ERα.and ERβ.In conclusion,PES1 interacts with ERαand ERβ.PES1 stabilizes the expression of ERα.and enhances its transcriptional activity.PES1 decreases the expression of ERβand attenuates its transcriptional activity.PES1 is the first coregulators identified which can inversely regulate the function of ERαand ERβ.PES1 may play a crucial role in the development of breast cancer and may be a new target of anti-tumor drug development.