Mutations in the dim-1 gene of Neurospora crassa reduce the level of DNA methylation (original) (raw)

Abstract

Mutants that show reduced DNA methylation were identified in a mutant screen based on the assumptions that (i) the nucleoside analog 5-azacytidine (5-azaC) promotes the formation of potentially lethal DNA-methyltransferase adducts; (ii) reduction in DNA methyltransferase will decrease the sensitivity of cells to 5-azaC; and (iii) this potential selective advantage will be enhanced in mutants that are deficient in the repair of 5-azaC-induced DNA damage. Of fifteen potential repair mutants screened for sensitivity to 5-azaC, five (mus-9, mus-10, mus-11, mus-18, and uvs-3) showed moderately increased sensitivity and two (mus-20, mei-3) showed highly increased sensitivity. A mus-20 mutation was used to isolate three non-complementing methylation mutants. The mutations, named dim-1 (_d_efective _i_n _m_ethylation), reduced female fertility, reduced methylation by 40–50%, and altered patterns of methylation. In wild-type strains hypomethylation perse fails to alter methylation specificity. We demonstrate a growth-phase-dependent change in methylation patterns, detectable only in hypomethylated DNA from dim + cultures. This may represent a growth-phase-dependent change in the relative amounts of distinct species of methyltransferase, one of which may be encoded by the dim-1 gene.

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Authors and Affiliations

  1. Institute of Molecular Biology, University of Oregon, Eugene, OR 97403–1229, USA Fax: +1-541-346-5891; e-mail: selker@molbio.uoregon.edu, , , , , , US
    H. M. Foss, C. J. Roberts & E. U. Selker

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  1. H. M. Foss
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  2. C. J. Roberts
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  3. E. U. Selker
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Received: 3 January 1998 / Accepted: 26 March 1998

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Foss, H., Roberts, C. & Selker, E. Mutations in the dim-1 gene of Neurospora crassa reduce the level of DNA methylation.Mol Gen Genet 259, 60–71 (1998). https://doi.org/10.1007/s004380050789

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