Change search
ReferencesLink to record
Permanent link

Direct link
RAD51 is Involved in Repair of Damage Associated with DNA Replication in Mammalian Cells
Stockholm University, Faculty of Social Sciences, Department of Applied Communications Science - GI and IHR.
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
2The Institute for Cancer Studies, University of Sheffield.
Show others and affiliations
2003 (English)In: Journal of Molecular Biology, ISSN 0022-2836, Vol. 328, no 3, 521-35 p.Article in journal (Refereed) Published
Abstract [en]

The RAD51 protein, a eukaryotic homologue of the Escherichia coli RecA protein, plays an important role in the repair of DNA double-strand breaks (DSBs) by homologous recombination (HR) in mammalian cells. Recent findings suggest that HR may be important in repair following replication arrest in mammalian cells. Here, we have investigated the role of RAD51 in the repair of different types of damage induced during DNA replication with etoposide, hydroxyurea or thymidine. We show that etoposide induces DSBs at newly replicated DNA more frequently than γ-rays, and that these DSBs are different from those induced by hydroxyurea. No DSB was found following treatment with thymidine. Although these compounds appear to induce different DNA lesions during DNA replication, we show that a cell line overexpressing RAD51 is resistant to all of them, indicating that RAD51 is involved in repair of a wide range of DNA lesions during DNA replication. We observe fewer etoposide-induced DSBs in RAD51-overexpressing cells and that HR repair of etoposide-induced DSBs is faster. Finally, we show that induced long-tract HR in the hprt gene is suppressed in RAD51-overexpressing cells, although global HR appears not to be suppressed. This suggests that overexpression of RAD51 prevents long-tract HR occurring during DNA replication. We discuss our results in light of recent models suggested for HR at stalled replication forks.

Place, publisher, year, edition, pages
Elsevier , 2003. Vol. 328, no 3, 521-35 p.
Keyword [en]
RAD51; mammalian cells; homologous recombination; stalled DNA replication forks; DNA double-strand breaks
National Category
Biological Sciences
Research subject
URN: urn:nbn:se:su:diva-23258DOI: 10.1016/S0022-2836(03)00313-9OAI: diva2:190947
Part of urn:nbn:se:su:diva-207Available from: 2004-08-20 Created: 2004-08-20 Last updated: 2010-01-07Bibliographically approved
In thesis
1. Homologous recombination at replication forks in mammalian cells
Open this publication in new window or tab >>Homologous recombination at replication forks in mammalian cells
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Accumulating evidence indicates that homologous recombination plays an important role in mammalian cells, primarily in the reactivation of stalled replication forks. During a normal round of replication, stalling of the replication fork occurs frequently when a nick or a lesion, which cannot be by-passed, is encountered. Progression of the replication fork can also be hindered by a protein bound to or secondary structures in the DNA. It is vital for the cell to restart stalled replication forks efficiently since nucleases might otherwise damage the unprotected DNA and since failure to reinitiate replication leads ultimately to cell death. The mechanism by which homologous recombination reactivates stalled replication forks and the substrates that trigger this response in mammalian cells have not yet been elucidated.

The present thesis focuses on the function of homologous recombination as well as on the mechanism for induction of this process in mammalian cells. Our major interest in this context was the repair of lesions encountered during replication and that interfere with replication fork progression. The role of the RAD51 protein in this process was also examined. The main experimental system we employed consisted of Chinese hamster cell lines deficient in different DNA repair pathways, as well as the V79 Chinese hamster SPD8 cell line, which contains an endogenous locus at which homologous recombination events can be monitored.

Our findings demonstrate that homologous recombination can be employed by mammalian cells to repair several different types of lesions encountered during replication. The mechanism underlying such homologous recombinational repair appears to depend on the type of lesion involved. A replication fork encountering a single-strand break was shown to collapse into a double-strand break and subsequently be repaired by homologous recombination involving a mechanism referred to as break-induced replication. A stalled replication fork was shown to induce a substrate for homologous recombination both with and without the induction of a double-strand break. This suggests that homologous recombination could repair lesions other than double-strand breaks during replication. Non-homologous end-joining was shown to play only a minor role in the repair of DNA damage associated with replication, being employed only in situations when the replication fork is processed into a double-strand break.

Experiments concerning the role of RAD51 in repair of lesions encountered during replication, employing a cell line that overexpresses this protein, indicated that RAD51 is rate limiting for the repair of DNA damage associated with the replication fork. The level of RAD51 was also measured in lung cancer cells and found to determine both the survival and the level of double-strand breaks formed in response to etoposide treatment, suggesting RAD51 to be involved in the resistance of tumours to chemotherapeutic drugs.

In summary, our findings demonstrate that RAD51-dependent homologous recombination is an important repair pathway during replication in mammalian cells.

Place, publisher, year, edition, pages
Stockholm: Institutionen för genetik, mikrobiologi och toxikologi, 2004. 64 p.
National Category
urn:nbn:se:su:diva-207 (URN)91-7265-922-X (ISBN)
Public defence
2004-09-10, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 13:00
Available from: 2004-08-20 Created: 2004-08-20Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Schultz, NiklasHelleday, Thomas
By organisation
Department of Applied Communications Science - GI and IHRDepartment of Genetics, Microbiology and Toxicology
Biological Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 50 hits
ReferencesLink to record
Permanent link

Direct link