| SMC2 forms the core ATPase subunit of condensin I and II complexes alongside SMC4 within the structural maintenance of chromosomes protein family, enabling chromosome compaction essential for mitotic segregation. The protein features N- and C-terminal nucleotide-binding domains that heterodimerize through a central hinge region, creating a ring-like structure that encircles chromatin while coiled-coil segments facilitate auxiliary subunit binding. SMC2-SMC4 heterodimers generate ATP-dependent positive supercoils in DNA when interacting with type II topoisomerases, driving axial chromosome shortening from prophase through anaphase while auxiliary subunits CAP-H/CAP-D/CAP-G (condensin I) or CAP-H2/CAP-D3/CAP-G2 (condensin II) modulate DNA-binding affinity and loop extrusion. Condensin II accumulates at centromeres during prometaphase, promoting H3S10 phosphorylation and sister chromatid resolution, whereas condensin I localizes along chromosome arms to maintain mitotic fidelity. ATPase activity cycles through ATP binding at the SMC2/SMC4 interface, head-head dimerization, hinge-mediated DNA capture, and powered translocation along chromatin fibers. Depletion expands mitotic chromosome volume, disrupts pericentromeric compaction, and impairs bipolar spindle attachment, leading to anaphase bridges and cytokinesis failure. Maternal SMC2 supports oocyte chromosome condensation and zygotic pronuclear congression, with knockout causing developmental arrest. In hyperproliferative states, β-catenin/TCF4 transcriptionally upregulates SMC2 to sustain rapid mitotic cycling in colorectal tumors. |
Lane 1: Hela, Lane 2: COS, Lane 3: H-4-II-E
