A Ubiquitin-Binding Domain in Cockayne Syndrome B Required for Transcription-Coupled Nucleotide Excision Repair

Summary

Transcription-coupled nucleotide excision repair (TC-NER) allows RNA polymerase II (RNAPII)-blocking lesions to be rapidly removed from the transcribed strand of active genes. Defective TCR in humans is associated with Cockayne syndrome (CS), typically caused by defects in either CSA or CSB. Here, we show that CSB contains a ubiquitin-binding domain (UBD). Cells expressing UBD-less CSB (CSB ^del) have phenotypes similar to those of cells lacking CSB, but these can be suppressed by appending a heterologous UBD, so ubiquitin binding is essential for CSB function. Surprisingly, CSB ^del remains capable of assembling nucleotide excision repair factors and repair synthesis proteins around damage-stalled RNAPII, but such repair complexes fail to excise the lesion. Together, our results indicate an essential role for protein ubiquitylation and CSB's UBD in triggering damage incision during TC-NER and allow us to integrate the function of CSA and CSB in a model for the process.

Abstract

Graphical Abstract

Highlights

► Cockayne syndrome B protein harbors a carboxy-terminal ubiquitin-binding domain (UBD) ► UBD deletion (CSB ^del) gives rise to the phenotypes typical of cells lacking CSB activity ► CSB ^del becomes immobilized at DNA lesions and no longer supports transcription reactiviation ► CSB ^del supports assembly of repair complexes, but these are incapable of damage incision