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Nature. 2018 Dec;564(7735):287-290. doi: 10.1038/s41586-018-0769-8. Epub 2018 Dec 5.

Dna2 nuclease deficiency results in large and complex DNA insertions at chromosomal breaks.

Yu Y1, Pham N1, Xia B2,3,4, Papusha A1, Wang G2,3,4, Yan Z1, Peng G5, Chen K6,7,8, Ira G9.

Author information

1
Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, TX, USA.
2
Center for Bioinformatics and Computational Biology, Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX, USA.
3
Institute for Academic Medicine, Houston Methodist Hospital, Houston, TX, USA.
4
Weill Cornell Medical College, Cornell University, Department of Cardiothoracic Surgery, New York, NY, USA.
5
Department of Clinical Cancer Prevention, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
6
Center for Bioinformatics and Computational Biology, Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX, USA. kchen2@houstonmethodist.org.
7
Institute for Academic Medicine, Houston Methodist Hospital, Houston, TX, USA. kchen2@houstonmethodist.org.
8
Weill Cornell Medical College, Cornell University, Department of Cardiothoracic Surgery, New York, NY, USA. kchen2@houstonmethodist.org.
9
Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, TX, USA. gira@bcm.edu.

Abstract

Insertions of mobile elements1-4, mitochondrial DNA5 and fragments of nuclear chromosomes6 at DNA double-strand breaks (DSBs) threaten genome integrity and are common in cancer7-9. Insertions of chromosome fragments at V(D)J recombination loci can stimulate antibody diversification10. The origin of insertions of chromosomal fragments and the mechanisms that prevent such insertions remain unknown. Here we reveal a yeast mutant, lacking evolutionarily conserved Dna2 nuclease, that shows frequent insertions of sequences between approximately 0.1 and 1.5 kb in length into DSBs, with many insertions involving multiple joined DNA fragments. Sequencing of around 500 DNA inserts reveals that they originate from Ty retrotransposons (8%), ribosomal DNA (rDNA) (15%) and from throughout the genome, with preference for fragile regions such as origins of replication, R-loops, centromeres, telomeres or replication fork barriers. Inserted fragments are not lost from their original loci and therefore represent duplications. These duplications depend on nonhomologous end-joining (NHEJ) and Pol4. We propose a model in which alternative processing of DNA structures arising in Dna2-deficient cells can result in the release of DNA fragments and their capture at DSBs. Similar DNA insertions at DSBs are expected to occur in any cells with linear extrachromosomal DNA fragments.

PMID:
30518856
PMCID:
PMC6346745
[Available on 2019-06-05]
DOI:
10.1038/s41586-018-0769-8

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