p27kip1 (p27) is a cdk-inhibitory protein with an important role in the proliferation of many cell types. SCFSkp2 is the best studied regulator of p27 levels, but Skp2-mediated p27 degradation is not essential in vivo or in vitro. The molecular pathway that compensates for loss of Skp2-mediated p27 degradation has remained elusive. Here, we combine vascular injury in the mouse with genome-wide profiling to search for regulators of p27 during cell cycling in vivo. This approach, confirmed by RT-qPCR and mechanistic analysis in primary cells, identified miR-221/222 as a compensatory regulator of p27. The expression of miR221/222 is sensitive to proteasome inhibition with MG132 suggesting a link between p27 regulation by miRs and the proteasome. We then examined the roles of miR-221/222 and Skp2 in cell cycle inhibition by prostacyclin (PGI2), a potent cell cycle inhibitor acting through p27. PGI2 inhibited both Skp2 and miR221/222 expression, but epistasis, ectopic expression, and time course experiments showed that miR-221/222, rather than Skp2, was the primary target of PGI2. PGI2 activates Gs to increase cAMP, and increasing intracellular cAMP phenocopies the effect of PGI2 on p27, miR-221/222, and mitogenesis. We conclude that miR-221/222 compensates for loss of Skp2-mediated p27 degradation during cell cycling, contributes to proteasome-dependent G1 phase regulation of p27, and accounts for the anti-mitogenic effect of cAMP during growth inhibition. © 2013 Castagnino et al.
P., C., D., K., E.A., H., S.-L., L., T., X., S., R., … R.K., A. (2013). miR-221/222 Compensates for Skp2-Mediated p27 Degradation and Is a Primary Target of Cell Cycle Regulation by Prostacyclin and cAMP. PLoS ONE, 8(2). https://doi.org/10.1371/journal.pone.0056140 LK - http://rug.on.worldcat.org/atoztitles/link/?sid=EMBASE&issn=19326203&id=doi:10.1371%2Fjournal.pone.0056140&atitle=miR-221%2F222+Compensates+for+Skp2-Mediated+p27+Degradation+and+Is+a+Primary+Target+of+Cell+Cycle+Regulation+by+Prostacyclin+and+cAMP&stitle=PLoS+ONE&title=PLoS+ONE&volume=8&issue=2&spage=&epage=&aulast=Castagnino&aufirst=Paola&auinit=P.&aufull=Castagnino+P.&coden=&isbn=&pages=-&date=2013&auinit1=P&auinitm=