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Condensin II complex subunit CAP-H2 or CNDH2, mid domain CNDH2_M is the middle domain of the H2 subunit of the condensin II complex, found in eukaryotes but not fungi. Eukaryotes carry at least two condensin complexes, I and II, each made up of five subunits. The functions of the two complexes are collaborative but non-overlapping. CI appears to be functional in G2 phase in the cytoplasm beginning the process of chromosomal lateral compaction while the CII are concentrated in the nucleus, possibly to counteract the activity of cohesion at this stage. In prophase, CII contributes to axial shortening of chromatids while CI continues to bring about lateral chromatid compaction, during which time the sister chromatids are joined centrally by cohesins. There appears to be just one condensin complex in fungi. CI and CII each contain SMC2 and SMC4 (structural maintenance of chromosomes) subunits, then CI has non-SMC CAP-D2 (CND1), CAP-G (CND3), and CAP-H (CND2). CII has, in addition to the two SMCs, CAP-D3, CAPG2 and CAP-H2. All four of the CAP-D and CAP-G subunits have degenerate HEAT repeats, whereas the CAP-H are kleisins or SMC-interacting proteins (ie they bind directly to the SMC subunits in the complex). The SMC molecules are each long with a small hinge-like knob at the free end of a longish strand, articulating with each other at the hinge. Each strand ends in a knob-like head that binds to one or other end of the CAP-H subunit. The HEAT-repeat containing D and G subunits bind side-by-side between the ends of the H subunit. Activity of the various parts of the complex seem to be triggered by extensive phosphorylations, eg, entry of the complex, in Sch.pombe, into the nucleus during mitosis is promoted by Cdk1 phosphorylation of SMC4/Cut3; and it has been shown that Cdk1 phosphorylates CAP-D3 at Thr1415 in He-La cells thus promoting early stage chromosomal condensation by CII. This region represents the disordered section of CNDH2 between the N- and the C-termini. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",