Spontaneous and double-strand break repair-associated quasipalindrome and frameshift mutagenesis in budding yeast: role of mismatch repair.

Autor:	Sugawara N; Department of Biology and Rosenstiel Basic Medical Sciences Research Center MS029, Brandeis University, Waltham, MA 02454-9110, USA., Towne MJ; Department of Biology and Rosenstiel Basic Medical Sciences Research Center MS029, Brandeis University, Waltham, MA 02454-9110, USA., Lovett ST; Department of Biology and Rosenstiel Basic Medical Sciences Research Center MS029, Brandeis University, Waltham, MA 02454-9110, USA., Haber JE; Department of Biology and Rosenstiel Basic Medical Sciences Research Center MS029, Brandeis University, Waltham, MA 02454-9110, USA.
Jazyk:	angličtina
Zdroj:	Genetics [Genetics] 2024 Jul 08; Vol. 227 (3).
DOI:	10.1093/genetics/iyae068
Abstrakt:	Although gene conversion (GC) in Saccharomyces cerevisiae is the most error-free way to repair double-strand breaks (DSBs), the mutation rate during homologous recombination is 1,000 times greater than during replication. Many mutations involve dissociating a partially copied strand from its repair template and re-aligning with the same or another template, leading to -1 frameshifts in homonucleotide runs, quasipalindrome (QP)-associated mutations and microhomology-mediated interchromosomal template switches. We studied GC induced by HO endonuclease cleavage at MATα, repaired by an HMR::KI-URA3 donor. We inserted into HMR::KI-URA3 an 18-bp inverted repeat where one arm had a 4-bp insertion. Most GCs yield MAT::KI-ura3::QP + 4 (Ura-) outcomes, but template-switching produces Ura+ colonies, losing the 4-bp insertion. If the QP arm without the insertion is first encountered by repair DNA polymerase and is then (mis)used as a template, the palindrome is perfected. When the QP + 4 arm is encountered first, Ura+ derivatives only occur after second-end capture and second-strand synthesis. QP + 4 mutations are suppressed by mismatch repair (MMR) proteins Msh2, Msh3, and Mlh1, but not Msh6. Deleting Rdh54 significantly reduces QP mutations only when events creating Ura+ occur in the context of a D-loop but not during second-strand synthesis. A similar bias is found with a proofreading-defective DNA polymerase mutation (poI3-01). DSB-induced mutations differed in several genetic requirements from spontaneous events. We also created a + 1 frameshift in the donor, expanding a run of 4 Cs to 5 Cs. Again, Ura+ recombinants markedly increased by disabling MMR, suggesting that MMR acts during GC but favors the unbroken, template strand. Competing Interests: Conflicts of interest The author(s) declare no conflict of interest. (© The Author(s) 2024. Published by Oxford University Press on behalf of The Genetics Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)
Databáze:	MEDLINE
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