The sequential and cooperative action of CSB, CSA and UVSSA targets the TFIIH complex to DNA damage-stalled RNA polymerase II

Abstract

Summary The response to DNA damage-stalled RNA polymerase II (RNAPIIo) involves the assembly of the transcription-coupled repair (TCR) complex on actively transcribed strands. The function of the TCR proteins CSB, CSA and UVSSA and the manner in which the core DNA repair complex, including transcription factor IIH (TFIIH), is recruited are largely unknown. Here, we define the assembly mechanism of the TCR complex in human isogenic knockout cells. We show that TCR is initiated by RNAPIIo-bound CSB, which recruits CSA through a newly identified CSA-interaction motif (CIM). Once recruited, CSA facilitates the association of UVSSA with stalled RNAPIIo. Importantly, we find that UVSSA is the key factor that recruits the TFIIH complex in a manner that is stimulated by CSB and CSA. Together these findings reveal a sequential and highly cooperative assembly mechanism of TCR proteins and reveal the mechanism for TFIIH recruitment to DNA damage-stalled RNAPIIo to initiate repair.

Repair, Removal, and Shutdown: It All Hinges on RNA Polymerase II Ubiquitylation

“…The subsequent assembly of the TC-NER machinery is dependent on K1268 ubiquitylation (Figure 1B). The association of the UVsensitive syndrome protein UVSSA with RNAPII and the subsequent ubiquitylation of UVSSA are needed for the recruitment of TFIIH to the stalled RNAPII and the removal of DNA damage (Nakazawa et al, 2020;van der Weegen et al, 2019). The following model for TC-NER may therefore be proposed (Figure 1B): Upon RNAPII stalling at a lesion, CSB/CSA and its associated ubiquitin ligase will bind RNAPII and contribute to the ubiquitylation of RPB1 at K1268.…”