Structural maintenance of chromosomes (SMC) proteins are critical regulators of chromosome organization and function (1).
This family of chromosomal ATPases is highly conserved from bacteria and archaeal species to vertebrates. There are at least six eukaryotic SMC proteins. The SMC proteins display a common primary architecture that consists of five structural domains.
The five domains include two nucleotide-binding motifs termed the Walker A and Walker B motifs located at the N- and C-terminus, a central “hinge” domain, and two coiled-coil motifs that flank the central “hinge”. The SMC proteins associate in specific dimer pairs and arrange in an anti-parallel, two-armed structure that folds into a V-shape at the “hinge” domain.
Three SMC complexes have been identified and are defined by the SMC subunits which associate to form a heterodimer and their respective associated proteins.
SMC1 and SMC3 are part of the cohesin holocomplex which also includes at least two non-SMC subunits Scc1/mcd1/rad21 and scc3/SAs. The cohesin complex is required for holding together sister chromatids after replication in S-phase and throughout G2 phase.
SMC2 and SMC4 are part of the condensin complex which also includes three non-SMC subunits: CAP-D2, CAP-G, and CAP-H. Condensin plays a critical role in mitotic chromosome condensation during prophase and metaphase and segregation of sister chromatids during anaphase.
and SMC6 are part of a not-yet-named octameric complex (2). The function of this complex is not fully understood; but it appears to be polyfunctional. The SMC5/SMC6 complex displays activities similar to cohesin and condensin, and it appears to be mainly involved in a variety of DNA repair pathways, replication, and recombination.
The necessity of SMC proteins to the chromosome cycle has been well demonstrated, and more studies of these factors are needed for a better understanding of the complex dynamics of chromosome structure and function.
1. T. Hirano, "The ABCs of SMC Proteins: Two-Armed ATPases for Chromosome Condensation, Cohesion, and Repair," Genes Dev. 16, no. 4 (2002): 399-414.
2. G. De Piccoli, J. Torres-Rosell, and L. Aragon, "The Unnamed Complex: What Do We Know About Smc5-Smc6?," Chromosome.Res. 17, no. 2 (2009): 251-263.
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Phospho SMC1 (S957)
Phospho SMC1 (S966)
Phospho SMC3 (S383)
Phospho SMC3 (S1083)
Antibodies to Condensin Complex Proteins ...