Mohd-Sarip, A., Lagarou, A., Doyen, C.M., van der Knaap, J.A., Aslan, A., Bezstarosti, K., Yassin, Y., Brock, H.W., Demmers, J.A., Verrijzer, C.P. (2012). Transcription-independent function of Polycomb group protein PSC in cell cycle control.  Science 336(6082): 744--747.

FBrf0218404

Research paper

Polycomb group (PcG) proteins control development and cell proliferation through chromatin-mediated transcriptional repression. We describe a transcription-independent function for PcG protein Posterior sex combs (PSC) in regulating the destruction of cyclin B (CYC-B). A substantial portion of PSC was found outside canonical PcG complexes, instead associated with CYC-B and the anaphase-promoting complex (APC). Cell-based experiments and reconstituted reactions established that PSC and Lemming (LMG, also called APC11) associate and ubiquitylate CYC-B cooperatively, marking it for proteosomal degradation. Thus, PSC appears to mediate both developmental gene silencing and posttranslational control of mitosis. Direct regulation of cell cycle progression might be a crucial part of the PcG system's function in development and cancer.