title: The LSH/DDM1 Homolog MUS-30 Is Required for Genome Stability, but Not for DNA Methylation in Neurospora crassa.
abstract: LSH/DDM1 enzymes are required for DNA methylation in higher eukaryotes and have poorly defined roles in genome maintenance in yeast, plants, and animals. The filamentous fungus Neurospora crassa is a tractable system that encodes a single LSH/DDM1 homolog (NCU06306). We report that the Neurospora LSH/DDM1 enzyme is encoded by mutagen sensitive-30 (mus-30), a locus identified in a genetic screen over 25 years ago. We show that MUS-30-deficient cells have normal DNA methylation, but are hypersensitive to DNA damaging agents. MUS-30 is a nuclear protein, consistent with its predicted role as a chromatin remodeling enzyme, and levels of MUS-30 are increased following DNA damage. MUS-30 co-purifies with Neurospora WDR76, a homolog of yeast Changed Mutation Rate-1 and mammalian WD40 repeat domain 76. Deletion of wdr76 rescued DNA damage-hypersensitivity of Δmus-30 strains, demonstrating that the MUS-30-WDR76 interaction is functionally important. DNA damage-sensitivity of Δmus-30 is partially suppressed by deletion of methyl adenine glycosylase-1, a component of the base excision repair machinery (BER); however, the rate of BER is not affected in Δmus-30 strains. We found that MUS-30-deficient cells are not defective for DSB repair, and we observed a negative genetic interaction between Δmus-30 and Δmei-3, the Neurospora RAD51 homolog required for homologous recombination. Together, our findings suggest that MUS-30, an LSH/DDM1 homolog, is required to prevent DNA damage arising from toxic base excision repair intermediates. Overall, our study provides important new information about the functions of the LSH/DDM1 family of enzymes.
authors.affiliation: Department of Microbiology, University of Georgia, Athens, Georgia, United States of America.
authors.forename: Evelina Y
authors.initials: EY
authors.lastname: Basenko
authors.affiliation: Department of Microbiology, University of Georgia, Athens, Georgia, United States of America.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kamei
authors.affiliation: Institute of Bioinformatics, University of Georgia, Athens, Georgia, United States of America.
authors.forename: Lexiang
authors.initials: L
authors.lastname: Ji
authors.affiliation: Department of Genetics, University of Georgia, Athens, Georgia, United States of America.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Schmitz
authors.affiliation: Department of Microbiology, University of Georgia, Athens, Georgia, United States of America.
authors.forename: Zachary A
authors.initials: ZA
authors.lastname: Lewis
mesh_terms: D042002:Chromatin Assembly and Disassembly / Q000235:genetics; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics; D004249:DNA Damage / Q000235:genetics*; D019175:DNA Methylation / Q000235:genetics; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics*; D042822:Genomic Instability; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics*
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D005656:Fungal Proteins