This group contains condensin-2 complex subunit D3. It is a regulatory subunit of the condensin-2 complex (contains the SMC2 and SMC4 heterodimer, and 3 non SMC subunits that probably regulate the complex: NCAPH2, NCAPD3 and NCAPG2), a complex which establishes mitotic chromosome architecture and is involved in physical rigidity of the chromatid axis [, ].
This entry includes condensin subunit 1 (CND1) and condensin-2 complex subunit D3 (NCAPD3).CND1 is a regulatory subunit of the condensin complex (contains the SMC2 and SMC4 heterodimer, and three non SMC subunits that probably regulate the complex: NCAPH/BRRN1, NCAPD2/CAPD2 and NCAPG), a complex required for conversion of interphase chromatin into mitotic-like condense chromosomes []. The condensin complex probably introduces positive supercoils into relaxed DNA in the presence of type I topoisomerases and converts nicked DNA into positive knotted forms in the presence of type II topoisomerases [, , , ]. NCAPD3 is a regulatory subunit of the condensin-2 complex (contains the SMC2 and SMC4 heterodimer, and 3 non SMC subunits that probably regulate the complex: NCAPH2, NCAPD3 and NCAPG2), a complex which establishes mitotic chromosome architecture and is involved in physical rigidity of the chromatid axis [].
The structural maintenance of chromosomes (SMC) proteins are large (approximately 110 to 170kDa), and each is arranged into five recognizable domains. Amino-acid sequence homology of SMC proteins between species is largely confined to the amino- and carboxy-terminal globular domains. The amino-terminal domain contains a 'Walker A' nucleotide-binding domain (GxxGxGKS/T), which by mutational studies has been shown to be essential in several proteins. The carboxy-terminal domain contains a sequence (the DA-box) that resembles a 'Walker B' motif, and a motif with homology to the signature sequence of the ATP-binding cassette (ABC) family of ATPases. The sequence homology within the carboxy-terminal domain is relatively high within the SMC1-SMC4 group, whereas SMC5 and SMC6 show some divergence in both of these sequences. In eukaryotic cells, the proteins are found as heterodimers of SMC1 paired with SMC3, SMC2 with SMC4, and SMC5 with SMC6 [].This entry represents the ATP-binding cassette domain of eukaryotic SMC4 proteins.
This entry includes condensin subunit 1 (CND1). CND1 is a regulatory subunit of the condensin complex (contains the SMC2 and SMC4 heterodimer, and three non SMC subunits that probably regulate the complex: NCAPH/BRRN1, NCAPD2/CAPD2 and NCAPG), a complex required for conversion of interphase chromatin into mitotic-like condense chromosomes []. The condensin complex probably introduces positive supercoils into relaxed DNA in the presence of type I topoisomerases and converts nicked DNA into positive knotted forms in the presence of type II topoisomerases [, , , ]. Condensin is a multi-subunit protein complex that acts as an essential regulator of chromosome condensation [, ]. It contains both SMC (structural maintenance of chromosomes) and non-SMC subunits. Condensin plays an important role during mitosis in the compaction and resolution of chromosomes to remove and prevent catenations that would otherwise inhibit segregation. This is thought to be achieved by the introduction of positive supercoils into relaxed DNA in the presence of type I topoisomerases and converts nicked DNA into positive knotted forms in the presence of type II topoisomerases. During interphase condensin promotes clustering of dispersed loci into subnuclear domains and inhibits associations between homologues. In meiosis, condensin has been shown to influence the number of crossover events by regulating programmed double-strand breaks. Roles in gene regulation and lymphocyte development have also been defined.
This is the middle domain of the H2 subunit of the condensin II complex, found in eukaryotes but not fungi. This region represents the disordered section of CNDH2 between the N- and the C-terminal domains.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 entry represents the N-terminal domain of the H2 subunit of the condensing II complex, found in eukaryotes but not in 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 is 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 [, ].
