The small CRL4^CSA ubiquitin ligase component DDA1 regulates transcription-coupled repair dynamics

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Cellular Aging

Background:

• Transcription-coupled nucleotide excision repair (TC-NER) removes DNA lesions to maintain cellular homeostasis and counteract aging.
• TC-NER is initiated by RNA polymerase II stalling, recruiting proteins like CSA, CSB, and UVSSA.
• The CSA protein is part of the CRL4^CSA ubiquitin ligase complex, but its regulation remains unclear.

Purpose of the Study:

• To investigate the regulation and molecular interactions of the CRL4^CSA complex in TC-NER.
• To identify novel interacting partners of CSA within the TC-NER pathway.
• To elucidate the role of DDA1 in the CRL4^CSA complex and its function in DNA repair.

Main Methods:

• Single-step protein-complex isolation coupled with mass spectrometry.
• Cryo-electron microscopy (Cryo-EM) for structural analysis.
• Functional assays to assess the role of DDA1 in TC-NER.

Main Results:

• DDA1 was identified as a novel interacting protein of CSA.
• Cryo-EM confirmed DDA1 as an integral component of the CRL4^CSA complex.
• DDA1 was found to coordinate ubiquitination dynamics and is essential for efficient TC-NER progression.

Conclusions:

• DDA1 is a key regulator of the CRL4^CSA complex in TC-NER.
• DDA1's role in ubiquitination dynamics is critical for the efficient turnover and progression of DNA repair.
• Understanding DDA1's function provides insights into maintaining cellular homeostasis and potentially counteracting aging.