Meiotic shugoshins differ from mitotic ones by arginine-reach C-terminal motif in yeast, plant, animals, and human
Background. Shugoshins (SGOs) are proteins that protect cohesins located at the centromeres of sister chromatids from their early cleavage during mitosis and meiosis in plants, fungi, and animals. Their function is to prevent premature sister-chromatid disjunction and segregation. Meiotic SGOs prevent segregation of sister chromatids in meiosis I, thus permitting homologous chromosomes to segregate and reduce chromosome number to haploid set. The study focused on the structural differences among shugoshins acting during mitosis and meiosis that cause differences in chromosome behavior in these two types of cell division in different organisms. Methods. A bioinformatics analysis of protein domains, conserved amino acid motifs, and physicochemical properties of 32 proteins from 25 species of plants, fungi, and animals was performed. Results. We identified a C-terminal arginine-reach amino acid motif that is highly evolutionarily conserved among the shugoshins protecting centromere cohesion of sister chromatids in meiotic anaphase I, but not among mitotic shugoshins. The motif looks like “arginine comb” capable of interaction by hydrogen bonds with guanine bases in the small groove of DNA helix. Shugoshins in different eukaryotic kingdoms differ also in the sets and location of amino acid motifs and the number of α-helical regions in the protein molecule. Discussion. Meiosis-specific arginine-reach motif may be responsible for formation of SGO-DNA nucleoprotein complex, thus protecting meiotic shugoshins from degradation during meiotic metaphase I and anaphase I, while mitotic SGOs have a motif with less number of arginine residues. This structural difference between meiotic and mitotic shugoshins, probably, could be a key molecular element of the prolonged shugoshin resistance to degradation during meiotic metaphase I and anaphase I and be one of the molecular elements causing the difference in chromosome behavior in meiosis and mitosis. The finding of differences in SGO structure in plant, fungi and animals supports idea of independent evolution of meiosis in different lineages of multicellular organisms.