Rad51 presynaptic filament stabilization function of the mouse Swi5-Sfr1 heterodimeric complex |
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Authors: | Tsai Shang-Pu Su Guan-Chin Lin Sheng-Wei Chung Chan-I Xue Xiaoyu Dunlop Myun Hwa Akamatsu Yufuko Jasin Maria Sung Patrick Chi Peter |
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Institution: | Institute of Biochemical Sciences, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei, 10617, Taiwan. |
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Abstract: | Homologous recombination (HR) represents a major error-free pathway to eliminate pre-carcinogenic chromosomal lesions. The DNA strand invasion reaction in HR is mediated by a helical filament of the Rad51 recombinase assembled on single-stranded DNA that is derived from the nucleolytic processing of the primary lesion. Recent studies have found that the human and mouse Swi5 and Sfr1 proteins form a complex that influences Rad51-mediated HR in cells. Here, we provide biophysical evidence that the mouse Swi5-Sfr1 complex has a 1:1 stoichiometry. Importantly, the Swi5-Sfr1 complex, but neither Swi5 nor Sfr1 alone, physically interacts with Rad51 and stimulates Rad51-mediated homologous DNA pairing. This stimulatory effect stems from the stabilization of the Rad51-ssDNA presynaptic filament. Moreover, we provide evidence that the RSfp (rodent Sfr1 proline rich) motif in Sfr1 serves as a negative regulatory element. These results thus reveal an evolutionarily conserved function in the Swi5-Sfr1 complex and furnish valuable information as to the regulatory role of the RSfp motif that is specific to the mammalian Sfr1 orthologs. |
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