SMC4
Description
The SMC4 (structural maintenance of chromosomes 4) is a protein-coding gene located on chromosome 3.
SMC-4, also known as chromosome-associated polypeptide C (CAP-C) or XCAP-C homolog, is a protein encoded by the SMC4 gene in humans. SMC-4 is a crucial subunit of condensin I and II, large protein complexes involved in high-order chromosome organization, including condensation and segregation. SMC-4 is commonly associated with the SMC-2 protein, forming a dimer. SMC-4 dimerizes with SMC-2, creating the flexible and dynamic structure of the condensin holocomplex. Overexpression of SMC-4 has been linked to carcinogenesis.
The basic structure of SMC proteins is characterized by a non-helical hinge group, separated by two anti-parallel α-helical coiled-coil domains, along with two Amino-terminal globular domains containing ATP hydrolytic sites. Dimerization occurs at the non-helical hinge group of SMC-4, which then associates with the non-helical hinge group of SMC-2, creating a V-shaped heterodimeric structure. The condensin holocomplex contains the SMC-4 and SMC-2 heterodimer subunits, along with 3 other non-SMC subunits, CAP-D2, CAP-G, and CAP-H. In the condensin holocomplex, a protein subunit called kleisin joins the C-terminus and N-terminus ATPase end domains of both SMC-4 and SMC-2 proteins.
SMC4 is a central component of the condensin complex, a crucial complex responsible for the transformation of interphase chromatin into condensed mitotic chromosomes. The condensin complex functions in DNA supercoiling, introducing positive supercoils into relaxed DNA in collaboration with type I topoisomerases. Furthermore, it converts nicked DNA into positive knotted forms in the presence of type II topoisomerases.
SMC4 is also known as CAP-C, CAPC, SMC-4, SMC4L1.
