Taylor, Elaine M. and Moghraby, Jeelan S. and Lees, Jennifer H. and Smit, Bep and Moens, Peter B. and Lehmann, Alan R. (2001) Characterization of a novel human SMC heterodimer homologous to the Schizosaccharomyces pombe Rad18/Spr18 complex. Molecular Biology of the Cell, 12 (6). pp. 1583-1594. ISSN 1059-1524
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Abstract
The structural maintenance of chromosomes (SMC) protein encoded by the fission yeast rad18 gene is involved in several DNA repair processes and has an essential function in DNA replication and mitotic control. It has a heterodimeric partner SMC protein, Spr18, with which it forms the core of a multiprotein complex. We have now isolated the human orthologues of rad18 andspr18 and designated them hSMC6 andhSMC5. Both proteins are about 1100 amino acids in length and are 27–28% identical to their fission yeast orthologues, with much greater identity within their N- and C-terminal globular domains. The hSMC6 and hSMC5 proteins interact to form a tight complex analogous to the yeast Rad18/Spr18 heterodimer. In proliferating human cells the proteins are bound to both chromatin and the nucleoskeleton. In addition, we have detected a phosphorylated form of hSMC6 that localizes to interchromatin granule clusters. Both the total level of hSMC6 and its phosphorylated form remain constant through the cell cycle. Both hSMC5 and hSMC6 proteins are expressed at extremely high levels in the testis and associate with the sex chromosomes in the late stages of meiotic prophase, suggesting a possible role for these proteins in meiosis.