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Transcription-associated recombination is independent of XRCC2 and mechanistically separate from homology-directed DNA double-strand break repair
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
2009 (English)In: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 37, no 2, 405-412 p.Article in journal (Refereed) Published
Abstract [en]

It has previously been shown that transcription greatly enhances recombination in mammalian cells. However, the proteins involved in catalysing this process and the recombination pathways involved in transcription-associated recombination (TAR) are still unknown. It is well established that both the BRCA2 protein and the RAD51 paralog protein XRCC2 are required for homologous recombination. Here, we show that the BRCA2 protein is also required for TAR, while the XRCC2 protein is not involved. Expression of the XRCC2 gene in XRCC2 mutated irs1 cells restores the defect in homologous recombination repair of an I-SceI-induced DNA double-strand break, while TAR is unaffected. Interestingly, the XRCC2-deficient irs1 cells are also proficient in recombination induced at slowed replication forks, suggesting that TAR is mechanistically linked with this recombination pathway. In conclusion, we show that TAR depends on BRCA2 but is independent of XRCC2, and that this recombination pathway is separate from that used to repair a two-ended DNA double-strand break.

Place, publisher, year, edition, pages
2009. Vol. 37, no 2, 405-412 p.
National Category
Microbiology in the medical area
URN: urn:nbn:se:su:diva-32012DOI: 10.1093/nar/gkn971ISI: 000262963400017PubMedID: 19043071OAI: diva2:279206
Available from: 2009-12-02 Created: 2009-12-02 Last updated: 2010-05-07Bibliographically approved
In thesis
1. Transcription Associated Recombination in Mammalian Cells
Open this publication in new window or tab >>Transcription Associated Recombination in Mammalian Cells
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is increasing evidence that the movement of the transcription machinery through DNA has profound effects on the genomic stability. One such example is a phenomenon known as Transcription Associated Recombination (TAR). Transcription enhances recombination levels to a high degree in all organisms studied, from bacteria to mammals. The underlying causes of the high recombination levels observed are unknown, as are the rationale for the rather riskyhazardous recombination event in this context. Recombination is not a risk-free event; there is e.g. the chancerisk for of loss of heterozygozity, which may eventually lead to tumour formation. So, why is TAR so ubiquitous? This thesis deals with the factors inducing TAR, trying to elucidate the mechanisms catalyzing this event. The proteins involved in executing TAR are unknown in mammals, and one of the aims of this thesis havehas been to investigate the role of well-known DNA repair proteins in TAR. In order to do so, cell lines deficient in crucial DNA repair proteins were stably transfected with a novel recombination construct. Transcription can be controlled over this recombination construct, enabling the detection of transcription associated recombination. We found that TAR is dependent on replication and that inhibition of transcription elongation had no further effect on TAR levels in our system. Further, we found that TAR employs a recombination pathway mechanistically separate from the recombination pathway induced by DNA double strand breaks. This pathway is dependent on BRCA2, a protein required for homologous recombination, but independent of the RAD51 paralog XRCC2. In subsequent studies, we found that the XPD subunit of the combined transcription and repair factor TFIIH is required for TAR, but is dispensable for DNA DSB repair by HR. We went on to investigate the connection between HR repair of UV damages and transcription and found that repair of UV damages requires transcription, but not via the transcription-coupled repair pathway. In conclusion, we found that TAR operates by a recombination pathway separate from DNA double strand break induced recombination. We found a connection with stalled replication, and revealed several of the proteins required for TAR in mammals.

Place, publisher, year, edition, pages
Stockholm: Department of Genetics, Microbiology and Toxicology, Stockholm University, 2010. 62 p.
National Category
Biological Sciences
Research subject
Molecular Genetics
urn:nbn:se:su:diva-38931 (URN)978-91-7447-079-6 (ISBN)
Public defence
2010-06-03, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.Available from: 2010-05-11 Created: 2010-05-04 Last updated: 2011-02-15Bibliographically approved

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