Apart from our investigation of the role of reversible PR SUMOylation, this microar ray dataset provides an updated well controlled analysis of WT PR B transcriptional action in response to progestin treatment. Rigorous independent experiments were per formed using additional cell lines and novel cell line clones expressing either constitutive http://www.selleckchem.com/products/Perifosine.html or inducible WT or mutant PRs, and gene Inhibitors,Modulators,Libraries expression levels were measured using distinct microarray platforms. Indeed, our analysis confirmed 70% of previously identified PR target genes but also uncovered hundreds of novel PR target genes, many of these are LI examples, we predicted that phospho Ser294 PRs mediate a shift in gene regulation that profoundly affects cancer cell phenotypes.

Thus, our goal in the current study was to identify these genes and understand the mechanism of their differential regula tion using entirely new breast can cer cell models. In cells stably expressing S294A PR, a receptor unable to be phosphorylated on Ser294 and thus heavily SUMOylated, the expression of selected KR upregulated Inhibitors,Modulators,Libraries genes was entirely blocked, transcriptional upregulation was rescued in cells expressing the PR K388R S294A double mutant. These data demon strate that PR SUMO modification dominantly represses transcription at PR target genes that are effectively derepressed in response to phosphorylation events. For example, PR dependent MSX2 and RGS2 mRNA expres sion was greatly augmented upon EGF treatment of cells expressing WT PR. We conclude that PR phosphorylation and deSUMOylation affects global gene expression patterns by dramatically altering PR transcriptional activity and promoter selectivity in breast cancer cells.

Mechanisms impacting PR promoter selectivity Our microarray studies clearly demonstrate that PR SUMO modification alters the expression of a broad range of PR target genes but has no effect on others. Little is known about the mechanisms of promoter selectivity. However, this question has been addressed with regard to other SR family members. SR inter actions with chromatin are highly Inhibitors,Modulators,Libraries dynamic and occur as a rapid and continuous exchange. Thus, concen trated regions of transcription factor binding actually reflect a shift in the equilibrium towards increased transcription factor occupancy at that region.

Multiple factors may influence this equilibrium, such as SR binding to consensus DNA sequences, parti cipation Inhibitors,Modulators,Libraries of coregulatory factors within multi protein Inhibitors,Modulators,Libraries complexes and selleck Brefeldin A or sequestration of SRs to specific cellu lar locations, as well as histone modifications that regu late chromatin accessibility. Additionally, studies of restriction enzymes have revealed mechanisms that facil itate enzyme binding to consensus sequences up to 1,000 times faster than is possible via diffusion alone, suggesting the existence of ancillary factors that facili tate binding.