XAB2 dynamics during DNA damage-dependent transcription inhibition

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Gene Expression Regulation

Background:

• Xeroderma Pigmentosum group A-binding protein 2 (XAB2) is a known multifunctional protein involved in transcription, splicing, DNA repair, and mRNA export.
• The precise role of XAB2 in DNA repair, particularly in Transcription-Coupled Nucleotide Excision Repair (TC-NER), remains incompletely understood.

Purpose of the Study:

• To elucidate the specific function of XAB2 in TC-NER pathways.
• To investigate the dynamic behavior of XAB2 in response to UV-induced DNA damage.
• To identify XAB2's interacting partners and cellular complexes during DNA repair.

Main Methods:

• Utilized UV-C irradiation to induce DNA damage in cellular models.
• Employed live-cell imaging techniques to track XAB2 mobility dynamics post-damage.
• Investigated protein-DNA and protein-protein interactions using co-immunoprecipitation and biochemical assays.

Main Results:

• XAB2 exclusively participates in TC-NER for RNA polymerase 2 (RNAP2)-transcribed genes.
• Unlike other NER proteins, XAB2 exhibits increased mobility after UV damage, with mobility restored upon repair completion.
• XAB2 is released from DNA:RNA hybrids (R-loops) and interacts with CSA and XPG proteins, facilitating RNAP2 release from UV lesions.

Conclusions:

• XAB2's dynamic release from R-loops and repair factors is essential for efficient DNA damage recognition in TC-NER.
• XAB2 plays a dual role, facilitating DNA repair and also retaining RNAP2 on its substrate in undamaged conditions.
• These findings reveal a novel mechanism for XAB2 in regulating RNAP2 dynamics during DNA repair and transcription.