High impact information on SMC3

• Cohesin's Smc1 and Smc3 "heads" are connected by an alpha kleisin subunit called Scc1, forming a tripartite ring with a diameter around 40 nm [1].
• Cleavage of the Smc3 coiled coil is sufficient to trigger cohesin release from chromosomes and loss of sister cohesion, consistent with a topological association with chromatin [2].
• Its Smc1 and Smc3 subunits are rod-shaped molecules with globular ABC-like ATPases at one end and dimerization domains at the other connected by long coiled coils [2].
• Both Rec8p and Smc3p colocalize with chromosome cores independently of synapsis during prophase I and largely disappear from chromosome arms after pachytene but persist in the neighborhood of centromeres until the onset of anaphase II [3].
• Meiotic cohesin REC8 marks the axial elements of rat synaptonemal complexes before cohesins SMC1beta and SMC3 [4].

Biological context of SMC3

• Association of mammalian SMC1 and SMC3 proteins with meiotic chromosomes and synaptonemal complexes [5].
• We report here evidence for an involvement of mammalian SMC1 and SMC3 proteins in meiosis [5].
• In Saccharomyces cerevisiae, a complex consisting of Scc1, Smc1, Smc3, and Scc3 proteins, called "cohesin," mediates the connection between sister chromatids [6].
• Furthermore, SMC1beta, SMC3, SCP2, and SCP3 cannot provide arm cohesion during metaphase I [4].
• RESULTS: Characterization of cohesin's ATPase activity suggests that hydrolysis depends on the binding of ATP to both Smc1 and Smc3 heads [7].

Anatomical context of SMC3

• In spermatocyte nuclei spreads, the SMC1 and SMC3 proteins localize in a beaded structure along the axial elements of synaptonemal complexes of pachytene and diplotene chromosomes [5].

Other interactions of SMC3

• Thus, SCC-1/COH-2 and the homologs of Scc3, Smc1, and Smc3 facilitate mitotic chromosome segregation during the development, presumably by forming a cohesin complex, whereas COH-1 seems to play a role important for development but unrelated to mitosis [8].
• C(2)M associates in vivo with the Smc3 cohesin subunit, as previously shown for yeast Rec8 [9].

References