Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)
Jeudi 4 novembre 2010
CUL4-DDB1 is required to maintain epigenetic gene repression via its interaction with the Arabidopsis PRC2 complex
Protein ubiquitylation regulates a broad variety of biological processes in alleukaryotes. Recent work identified a novel class of cullin-RING ligase (CRL)composed of CUL4, DDB1, and one substrate receptor also called DCAF (DDB1 andCUL4-associated factors). DCAFs are WD40 proteins containing WDxR motifs thatare required for efficient binding to DDB1. In both human and Arabidopsis, about 90different DCAFs have been predicted, but for most of them their function orsubstrates remain still unknown.Among putative Arabidopsis DCAFs we identified MSI1, which belongs to anevolutionary conserved protein family. MSI1-like proteins contribute to differentprotein complexes, including the epigenetic regulatory Polycomb RepressiveComplex2 (PRC2). Here we will present evidence that Arabidopsis MSI1 physicallyinteracts with DDB1 and is part of a multimeric CRL4-type E3 complex. Interestinglythe CUL4-DDB1MSI1 complex is required to maintain parental imprinting of MEA, atarget gene of the Arabidopsis PRC2 complex. Moreover, we extended these studiesto another MSI1-like protein, called MSI4/FVE, which is involved in the regulation offlowering time. Overall, we will discuss the mechanism by which CRL4s are requiredto maintain Polycomb-mediated gene repression.
Contact : Frédéric Gaymard