Cdk11-Cyclin L controls the assembly of the RNA polymerase II Mediator [expression]

The L-Mediator is a general co-activator of RNA Polymerase II transcription and is formed by the reversible association of the S-Mediator and the kinase module harbouring Cdk8. We describe the Cdk11-Lcp1 complex and show that its inactivation alter the global expression profiles in a very similar way than mutations of the kinase module. Cdk11 is broadly distributed onto chromatin and phosphorylate the Med27 and Med4 Mediator subunits on conserved residues. The inactivation of either Cdk11 or the mutation of its target residues on the Mediator leads to a strongly decreased association of the kinase module and the S-Mediator. The results show that Cdk11-Lcp1 regulates that assembly of the L-Mediator complex. Total RNA was isolated from two biological replicates for all conditions, and each biological replicate was hybridized in duplicate on Agilent arrays (dye-swap).