The base excision repair (BER) glycosylase MUTYH (Homo sapiens) serves a vital role in removing A opposite 8-oxo-7,8-dihydroguanine (OG). The inheritance of MUTYH gene defects results in an accumulation of G:C to T:A transversion mutations, as identified in the adenomas and carcinomas of MUTYH Associated Polyposis (MAP) patients. Many of the currently identified MAP variants are amino acids changes localized adjacent to the enzyme’s essential metal cofactor binding sites. One of these cofactors is a [4Fe-4S]2+ cluster coordinated to four Cys residues located in the N-terminal catalytic domain of nearly all MutY/MUTYH homologs. In addition, in mammalian MUTYH homologs there is a second cofactor, a Zn2+ linchpin motif localized within an extended region of the interdomain connector (IDC). In vitro and in vivo functional assays have demonstrated that correct Zn2+ coordination within MUTYH is crucial for repair and Fe-S cluster retention. In this study, massive sequence alignments, computational modeling, and circular dichroism was employed to determine the coordination sphere of the Zn2+ linchpin using the Mutyh (Mus musculus) homolog. In addition, fluorescent polarization binding studies and ROS response assays demonstrate that Zn2+ coordination regulates MUTYH repair activity and may have implications in downstream BER processes. These findings provide insight into the detrimental consequences of MAP variants adjacent to the critical cofactors of MUTYH.

Complete Zn2+ linchpin coordination sphere of the DNA repair glycosylase MUTYH

253rd National Meeting (2017)

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