Cockayne’s Syndrome A and B Proteins Regulate Transcription Arrest after Genotoxic Stress by Promoting ATF3 Degradation

Abstract

Cockayne syndrome (CS) is caused by mutations in CSA and CSB. The CSA and CSB proteins have been linked to both promoting transcription-coupled repair and restoring transcription following DNA damage. We show that UV stress arrests transcription of approximately 70% of genes in CSA- or CSB-deficient cells due to the constitutive presence of ATF3 at CRE/ATF sites. We found that CSB, CSA/DDB1/CUL4A, and MDM2 were essential for ATF3 ubiquitination and degradation by the proteasome. ATF3 removal was concomitant with the recruitment of RNA polymerase II and the restart of transcription. Preventing ATF3 ubiquitination by mutating target lysines prevented recovery of transcription and increased cell death following UV treatment. Our data suggest that the coordinate action of CSA and CSB, as part of the ubiquitin/proteasome machinery, regulates the recruitment timing of DNA-binding factors and provide explanations about the mechanism of transcription arrest following genotoxic stress.

Mechanistic insights into the regulation of transcription and transcription-coupled DNA repair by Cockayne syndrome protein B

“…In CSB-deficient cells, however, the ATF3 protein and ATF3 occupancy at its target promoters remain high (64). This work suggested that CSB might be required to remove ATF3 from its target promoters to allow transcription resumption (Figure 2), and this hypothesis was subsequently tested (53). It was found that CSB collaborates with Cockayne syndrome protein A (CSA) to promote the ubiquitination and degradation of ATF3, thereby allowing transcription to resume (Figure 2).…”

“…However, CSB contains a ubiquitin-binding domain (UBD) in its C-terminal region, which is absent in its yeast homologs (Figure 1). This domain is suggested to be critical for CSB function in TC-NER as well as transcription (52,53) and is likely specific to CSB’s role in multicellular organism development.…”

“…Recent studies have suggested that the inability to reactivate transcription in Cockayne syndrome cells after UV irradiation may be due, in part, to an inability to relieve general transcriptional repression induced by UV irradiation (53,64). Kristensen et al .…”

Heterogeneity and overlaps in nucleotide excision repair disorders

“…Transcriptional dysregulation upon UV irradiation is also observed in XP‐B/CS and XP‐G/CS cells, although apparently not related to Sirt1 impairment . Interestingly, it has been recently shown that UV irradiation persistently arrests transcription of about 70% of genes in CS patient cells defective in either CSA or CSB, because of the constitutive presence of the ATF3 repressor …”

“…54 Interestingly, it has been recently shown that UV irradiation persistently arrests transcription of about 70% of genes in CS patient cells defective in either CSA or CSB, because of the constitutive presence of the ATF3 repressor. 55 An additional model suggests that the molecular alterations under- Mitochondria function as the "powerplant" of the cells and supply ATP by oxidative phosphorylation, a process that induces the production of high levels of ROS. As a consequence, mitochondrial DNA (mtDNA) is constantly exposed to oxidative stress leading to damage accumulation.…”