title: ASCIZ regulates lesion-specific Rad51 focus formation and apoptosis after methylating DNA damage.
abstract: Nuclear Rad51 focus formation is required for homology-directed repair of DNA double-strand breaks (DSBs), but its regulation in response to non-DSB lesions is poorly understood. Here we report a novel human SQ/TQ cluster domain-containing protein termed ASCIZ that forms Rad51-containing foci in response to base-modifying DNA methylating agents but not in response to DSB-inducing agents. ASCIZ foci seem to form prior to Rad51 recruitment, and an ASCIZ core domain can concentrate Rad51 in focus-like structures independently of DNA damage. ASCIZ depletion dramatically increases apoptosis after methylating DNA damage and impairs Rad51 focus formation in response to methylating agents but not after ionizing radiation. ASCIZ focus formation and increased apoptosis in ASCIZ-depleted cells depend on the mismatch repair protein MLH1. Interestingly, ASCIZ foci form efficiently during G1 phase, when sister chromatids are unavailable as recombination templates. We propose that ASCIZ acts as a lesion-specific focus scaffold in a Rad51-dependent pathway that resolves cytotoxic repair intermediates, most likely single-stranded DNA gaps, resulting from MLH1-dependent processing of base lesions.
authors.affiliation: St Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.
authors.forename: Carolyn J
authors.initials: CJ
authors.lastname: McNees
authors.forename: Lindus A
authors.initials: LA
authors.lastname: Conlan
authors.forename: Nora
authors.initials: N
authors.lastname: Tenis
authors.forename: Jörg
authors.initials: J
authors.lastname: Heierhorst
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis; D020137:Base Pair Mismatch; D002352:Carrier Proteins; D045744:Cell Line, Tumor; D002470:Cell Survival; D004249:DNA Damage; D019175:DNA Methylation; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000502:physiology; D009687:Nuclear Proteins / Q000502:physiology*; D017434:Protein Structure, Tertiary; D051135:Rad51 Recombinase; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D000070957:MutL Protein Homolog 1