Nucleic Acids Research Advance Access published online on September 18, 2009
Nucleic Acids Research, doi:10.1093/nar/gkp753
Nucleic Acid Enzymes |
A SRS2 homolog from Arabidopsis thaliana disrupts recombinogenic DNA intermediates and facilitates single strand annealing
Botanical Institute II, Karlsruhe Institute of Technology (KIT), Kaiserstr. 12, 76128 Karlsruhe, Germany
*To whom correspondence should be addressed. Tel: +49 721 608 8894; Fax: +49 608 4874; Email: holger.puchta{at}bio.uka.de
Received June 17, 2009. Revised August 27, 2009. Accepted August 27, 2009.
Genetic and biochemical analyses of SRS2 homologs in fungi indicate a function in the processing of homologous recombination (HR) intermediates. To date, no SRS2 homologs have been described and analyzed in higher eukaryotes. Here, we report the first biochemical characterization of an SRS2 homolog from a multicellular eukaryote, the plant Arabidopsis thaliana. We studied the basic properties of AtSRS2 and were able to show that it is a functional 3'- to 5'-helicase. Furthermore, we characterized its biochemical function on recombinogenic intermediates and were able to show the unwinding of nicked Holliday junctions (HJs) and partial HJs (PX junctions). For the first time, we demonstrated strand annealing activity for an SRS2 homolog and characterized its strand pairing activity in detail. Our results indicate that AtSRS2 has properties that enable it to be involved in different steps during the processing of recombination intermediates. On the one hand, it could be involved in the unwinding of an elongating invading strand from a donor strand, while on the other hand, it could be involved in the annealing of the elongated strand at a later step.