The structure and evolution of the MaSMC4 gene of common vole Microtus arvalis (Arvicolidae, Rodentia)

In eukaryotes, the SMC (Structural Maintenance of Chromosomes) gene family is represented by at least six genes. Some of these genes have tissue-specific homologs. Eukaryotic SMC structural proteins are the members of biochemical complexes responsible for cohesion of sister chromatids, recombination, repair, regulation of gene expression, and formation of mitotic chromosomes. In the present study, the structure of the SMC4 subfamily gene was examined in common vole Microtus arvalis. Comparative analysis of rodent (M. arvalis, Mus musculus, and Rattus norvegicus), human, and Xenopus laevis SMC4 orthologous genes was carried out, and the main patterns of their organization and regulation were established. The SMC4 genes contain 24 exons; open reading frame starts at exon 2. The SMC4 5' regions contain the CpG islands, extending in the region of exon-intron 1 and exon 2. The SMC4 genes are characterized by the presence of multiple transcription startpoints. The region of the major transcription startpoint contains the INR CCA sub(+1)TTTT element. The SMC4 5' region is characterized by the presence of putative binding site for basal transcription factor Sp1 and factor E2F, typical of the genes induced in the G1/S phase of the cell cycle. The divergence level of the SMC4 coding region was examined. The mean Ka/Ks ratio for the SMC4 genes examined was 0.123. The region of exon 2 was found to be the most variable (Ka/Ks = 0.715), while the most conservative was the region coding for the C-globular domain, which contained the DA box (Ka/Ks = 0.024).