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The Mre11/Rad50/Xrs2 complex and non-homologous end-joining of incompatible ends in S. cerevisiae.
DNA Repair (Amst). 2005 Nov 21; 4(11):1281-94.DR

Abstract

In Saccharomyces cerevisiae, the Mre11/Rad50/Xrs2 (MRX) complex plays important roles in both homologous and non-homologous pathways of DNA repair. In this study, we investigated the role of the MRX complex and its enzymatic functions in non-homologous repair of DNA ends containing incompatible end structures. Using a plasmid transformation assay, we found that mre11 and rad50 null strains are extremely deficient in joining of incompatible DNA ends. Expression of the nuclease-deficient Mre11 mutant H125N fully complemented the mre11 strain for joining of mismatched ends in the absence of homology, while a mutant of Rad50 deficient in ATP-dependent activities exhibited levels of end-joining similar to a rad50 deletion strain. Although the majority of non-homologous end-joining (NHEJ) products isolated did not contain microhomologies, introduction of an 8bp microhomology at mismatched ends resulted in microhomology-mediated joining in all of the products recovered, demonstrating that a microhomology exerts a dominant effect on processing events that occur during NHEJ. Nuclease-deficient Mre11p was less efficient in promoting microhomology-mediated end-joining in comparison to its ability to stimulate non-microhomology-mediated events, suggesting that Mre11p influences, but is not essential for, microhomology-mediated repair. When the linearized DNA was transformed in the presence of an intact homologous plasmid to facilitate gap repair, there was no decrease in NHEJ products obtained, suggesting that NHEJ and homologous repair do not compete for DNA ends in vivo. These results suggest that the MRX complex is essential for joining of incompatible ends by NHEJ, and the ATP-dependent activities of Rad50 are critical for this process.

Authors+Show Affiliations

Department of Molecular Genetics and Microbiology, University of Texas at Austin, 1 University Station, A4800, Austin, TX 78712-0159, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

16043424

Citation

Zhang, Xiaoming, and Tanya T. Paull. "The Mre11/Rad50/Xrs2 Complex and Non-homologous End-joining of Incompatible Ends in S. Cerevisiae." DNA Repair, vol. 4, no. 11, 2005, pp. 1281-94.
Zhang X, Paull TT. The Mre11/Rad50/Xrs2 complex and non-homologous end-joining of incompatible ends in S. cerevisiae. DNA Repair (Amst). 2005;4(11):1281-94.
Zhang, X., & Paull, T. T. (2005). The Mre11/Rad50/Xrs2 complex and non-homologous end-joining of incompatible ends in S. cerevisiae. DNA Repair, 4(11), 1281-94.
Zhang X, Paull TT. The Mre11/Rad50/Xrs2 Complex and Non-homologous End-joining of Incompatible Ends in S. Cerevisiae. DNA Repair (Amst). 2005 Nov 21;4(11):1281-94. PubMed PMID: 16043424.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The Mre11/Rad50/Xrs2 complex and non-homologous end-joining of incompatible ends in S. cerevisiae. AU - Zhang,Xiaoming, AU - Paull,Tanya T, Y1 - 2005/07/25/ PY - 2005/05/29/received PY - 2005/06/23/revised PY - 2005/06/23/accepted PY - 2005/7/27/pubmed PY - 2008/7/25/medline PY - 2005/7/27/entrez SP - 1281 EP - 94 JF - DNA repair JO - DNA Repair (Amst) VL - 4 IS - 11 N2 - In Saccharomyces cerevisiae, the Mre11/Rad50/Xrs2 (MRX) complex plays important roles in both homologous and non-homologous pathways of DNA repair. In this study, we investigated the role of the MRX complex and its enzymatic functions in non-homologous repair of DNA ends containing incompatible end structures. Using a plasmid transformation assay, we found that mre11 and rad50 null strains are extremely deficient in joining of incompatible DNA ends. Expression of the nuclease-deficient Mre11 mutant H125N fully complemented the mre11 strain for joining of mismatched ends in the absence of homology, while a mutant of Rad50 deficient in ATP-dependent activities exhibited levels of end-joining similar to a rad50 deletion strain. Although the majority of non-homologous end-joining (NHEJ) products isolated did not contain microhomologies, introduction of an 8bp microhomology at mismatched ends resulted in microhomology-mediated joining in all of the products recovered, demonstrating that a microhomology exerts a dominant effect on processing events that occur during NHEJ. Nuclease-deficient Mre11p was less efficient in promoting microhomology-mediated end-joining in comparison to its ability to stimulate non-microhomology-mediated events, suggesting that Mre11p influences, but is not essential for, microhomology-mediated repair. When the linearized DNA was transformed in the presence of an intact homologous plasmid to facilitate gap repair, there was no decrease in NHEJ products obtained, suggesting that NHEJ and homologous repair do not compete for DNA ends in vivo. These results suggest that the MRX complex is essential for joining of incompatible ends by NHEJ, and the ATP-dependent activities of Rad50 are critical for this process. SN - 1568-7864 UR - https://www.unboundmedicine.com/medline/citation/16043424/The_Mre11/Rad50/Xrs2_complex_and_non_homologous_end_joining_of_incompatible_ends_in_S__cerevisiae_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1568-7864(05)00148-5 DB - PRIME DP - Unbound Medicine ER -