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The Saccharomyces cerevisiae Mre11-Rad50-Xrs2 complex promotes trinucleotide repeat expansions independently of homologous recombination.
DNA Repair (Amst). 2016 07; 43:1-8.DR

Abstract

Trinucleotide repeats (TNRs) are tandem arrays of three nucleotides that can expand in length to cause at least 17 inherited human diseases. Somatic expansions in patients can occur in differentiated tissues where DNA replication is limited and cannot be a primary source of somatic mutation. Instead, mouse models of TNR diseases have shown that both inherited and somatic expansions can be suppressed by the loss of certain DNA repair factors. It is generally believed that these repair factors cause misprocessing of TNRs, leading to expansions. Here we extend this idea to show that the Mre11-Rad50-Xrs2 (MRX) complex of Saccharomyces cerevisiae is a causative factor in expansions of short TNRs. Mutations that eliminate MRX subunits led to significant suppression of expansions whereas mutations that inactivate Rad51 had only a minor effect. Coupled with previous evidence, this suggests that MRX drives expansions of short TNRs through a process distinct from homologous recombination. The nuclease function of Mre11 was dispensable for expansions, suggesting that expansions do not occur by Mre11-dependent nucleolytic processing of the TNR. Epistasis between MRX and post-replication repair (PRR) was tested. PRR protects against expansions, so a rad5 mutant gave a high expansion rate. In contrast, the mre11 rad5 double mutant gave a suppressed expansion rate, indistinguishable from the mre11 single mutant. This suggests that MRX creates a TNR substrate for PRR. Protein acetylation was also tested as a mechanism regulating MRX activity in expansions. Six acetylation sites were identified in Rad50. Mutation of all six lysine residues to arginine gave partial bypass of a sin3 HDAC mutant, suggesting that Rad50 acetylation is functionally important for Sin3-mediated expansions. Overall we conclude that yeast MRX helps drive expansions of short TNRs by a mechanism distinct from its role in homologous recombination and independent of the nuclease function of Mre11.

Authors+Show Affiliations

Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, University Road, Galway, Ireland; College of Crop Science, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, University Road, Galway, Ireland; NCBES Galway Neuroscience Centre, School of Natural Sciences, National University of Ireland, Galway University Road, Galway, Ireland.Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, University Road, Galway, Ireland; NCBES Galway Neuroscience Centre, School of Natural Sciences, National University of Ireland, Galway University Road, Galway, Ireland. Electronic address: bob.lahue@nuigalway.ie.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

27173583

Citation

Ye, Yanfang, et al. "The Saccharomyces Cerevisiae Mre11-Rad50-Xrs2 Complex Promotes Trinucleotide Repeat Expansions Independently of Homologous Recombination." DNA Repair, vol. 43, 2016, pp. 1-8.
Ye Y, Kirkham-McCarthy L, Lahue RS. The Saccharomyces cerevisiae Mre11-Rad50-Xrs2 complex promotes trinucleotide repeat expansions independently of homologous recombination. DNA Repair (Amst). 2016;43:1-8.
Ye, Y., Kirkham-McCarthy, L., & Lahue, R. S. (2016). The Saccharomyces cerevisiae Mre11-Rad50-Xrs2 complex promotes trinucleotide repeat expansions independently of homologous recombination. DNA Repair, 43, 1-8. https://doi.org/10.1016/j.dnarep.2016.04.012
Ye Y, Kirkham-McCarthy L, Lahue RS. The Saccharomyces Cerevisiae Mre11-Rad50-Xrs2 Complex Promotes Trinucleotide Repeat Expansions Independently of Homologous Recombination. DNA Repair (Amst). 2016;43:1-8. PubMed PMID: 27173583.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The Saccharomyces cerevisiae Mre11-Rad50-Xrs2 complex promotes trinucleotide repeat expansions independently of homologous recombination. AU - Ye,Yanfang, AU - Kirkham-McCarthy,Lucy, AU - Lahue,Robert S, Y1 - 2016/05/02/ PY - 2015/10/29/received PY - 2016/04/29/revised PY - 2016/04/29/accepted PY - 2016/5/14/entrez PY - 2016/5/14/pubmed PY - 2017/5/16/medline KW - Expansion KW - Homologous recombination KW - Mre11-Rad50-Xrs2 complex KW - Neurological disease KW - Trinucleotide repeat SP - 1 EP - 8 JF - DNA repair JO - DNA Repair (Amst) VL - 43 N2 - Trinucleotide repeats (TNRs) are tandem arrays of three nucleotides that can expand in length to cause at least 17 inherited human diseases. Somatic expansions in patients can occur in differentiated tissues where DNA replication is limited and cannot be a primary source of somatic mutation. Instead, mouse models of TNR diseases have shown that both inherited and somatic expansions can be suppressed by the loss of certain DNA repair factors. It is generally believed that these repair factors cause misprocessing of TNRs, leading to expansions. Here we extend this idea to show that the Mre11-Rad50-Xrs2 (MRX) complex of Saccharomyces cerevisiae is a causative factor in expansions of short TNRs. Mutations that eliminate MRX subunits led to significant suppression of expansions whereas mutations that inactivate Rad51 had only a minor effect. Coupled with previous evidence, this suggests that MRX drives expansions of short TNRs through a process distinct from homologous recombination. The nuclease function of Mre11 was dispensable for expansions, suggesting that expansions do not occur by Mre11-dependent nucleolytic processing of the TNR. Epistasis between MRX and post-replication repair (PRR) was tested. PRR protects against expansions, so a rad5 mutant gave a high expansion rate. In contrast, the mre11 rad5 double mutant gave a suppressed expansion rate, indistinguishable from the mre11 single mutant. This suggests that MRX creates a TNR substrate for PRR. Protein acetylation was also tested as a mechanism regulating MRX activity in expansions. Six acetylation sites were identified in Rad50. Mutation of all six lysine residues to arginine gave partial bypass of a sin3 HDAC mutant, suggesting that Rad50 acetylation is functionally important for Sin3-mediated expansions. Overall we conclude that yeast MRX helps drive expansions of short TNRs by a mechanism distinct from its role in homologous recombination and independent of the nuclease function of Mre11. SN - 1568-7856 UR - https://www.unboundmedicine.com/medline/citation/27173583/The_Saccharomyces_cerevisiae_Mre11_Rad50_Xrs2_complex_promotes_trinucleotide_repeat_expansions_independently_of_homologous_recombination_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1568-7864(15)30098-7 DB - PRIME DP - Unbound Medicine ER -