Component of the Cdk8 module/Srb8-11 module which is a regulatory module of the Mediator complex that regulates basal RNA polymerase II transcription. The Cdk8 module may sterically hinder the interaction between Mediator and RNA polymerase II leading to transcriptional repression of a subset of genes regulated by Mediator. Component of the Cdk8 module of the Mediator complex. The Cdk8 module is composed of srb8, srb9, srb10 and srb11. Belongs to the cyclin family. Cyclin C subfamily.