Transcription-dependent polyubiquitination of RNA polymerase II requires lysine 63 of ubiquitin.

Lysine-63-linked polyubiquitin chains are not thought to signal protein degradation but instead signal for a variety of cellular processes including some types of DNA repair. RNA polymerase (Pol) II is polyubiquitinated following DNA damage or upon treatment of nuclear extracts with the transcription inhibitor alpha-amanitin. Here, we report, using a reaction in vitro, that transcription-dependent polyubiquitination of RNA Pol II consists of lysine-63-linked chains. This modification is specific for RNA Pol II engaged in active transcription and arrested by alpha-amanitin.