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Science 336 (6082): 744-747

Copyright © 2012 by the American Association for the Advancement of Science

Transcription-Independent Function of Polycomb Group Protein PSC in Cell Cycle Control

Adone Mohd-Sarip,1 Anna Lagarou,1,*,{dagger} Cecile M. Doyen,1,{dagger} Jan A. van der Knaap,1,{dagger} Ülkü Aslan,1 Karel Bezstarosti,2 Yasmin Yassin,3 Hugh W. Brock,3 Jeroen A. A. Demmers,2 C. Peter Verrijzer1,{ddagger}

Abstract: 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.

1 Department of Biochemistry and Centre for Biomedical Genetics, Erasmus University Medical Centre, Post Office Box 1738, 3000 DR, Rotterdam, Netherlands.
2 Proteomics Centre, Erasmus University Medical Centre, Post Office Box 1738, 3000 DR, Rotterdam, Netherlands.
3 Department of Zoology, University of British Columbia, Vancouver, BC, Canada.

* Present address: Biomedical Sciences Research Center Alexander Fleming, 16672 Vari, Greece.

{dagger} These authors contributed equally to this work.

{ddagger} To whom correspondence should be addressed. E-mail: c.verrijzer{at}

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