The High Mobility Group Domain Protein Cmb1 ofSchizosaccharomyces pombeBinds to Cytosines in Base Mismatches and Opposite Chemically Altered Guanines

Oliver Fleck, Christophe Kunz, Claudia Rudolph, Jürg Kohli
1998 Journal of Biological Chemistry  
The mismatch-binding activity Cmb1 of Schizosaccharomyces pombe was enriched from wild type cells, and N-terminal sequencing enabled cloning of the respective gene. The deduced amino acid sequence of cmb1 ؉ contains a high mobility group domain, a motif that is common to a heterogeneous family of DNA-binding proteins. In crude protein extracts of a cmb1 gene-disruption strain, specific binding to C/T, C/A, and C/⌬ was abolished. Weak binding to C/C revealed the presence of a second
more » ... ing activity, Cmb2. Cmb1, enriched from S. pombe and purified from Escherichia coli, bound specifically to C/C, C/T, C/A, T/T, and C/⌬ but showed little or no affinity to other mismatches and small loops. Cmb1 recognizes 1,2 GpG intrastrand crosslinks, produced by the chemotherapeutic drug cisplatin, when two cytosines are opposite the cross-linked guanines but not when other bases are present. Consistently, O 6 -methylguanine:C but not O 6 -methylguanine/T lesions were bound. Thus, cytosines in mismatches and opposite chemically modified guanines are the preferred target of Cmb1 recognition. cmb1 mutant cells are more sensitive to cisplatin than wild type cells, indicating a role of Cmb1 in repair of cisplatin-induced DNA damage.
doi:10.1074/jbc.273.46.30398 pmid:9804804 fatcat:3s33mvnozbcchpcr6qfkbbrldy