Condensins

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Schematic illustration of Condensin with the names of the individual subunits.

Conde Sine are protein complexes that for chromosome condensation of mitosis are required.

properties

Structurally, condensins are very similar to cohesins , but differ in function. They consist of five subunits: two SMC proteins (SMC2 and SMC4), one Kleisin (Brn1 / CAP-H or CAP-H2) and two HEAT repeat proteins (CAP-D2 / D3 and CAP-G / G2). Both SMC subunits form a ring with the Kleisin subunit. It has been suggested that this ring, similar to Cohesin, can topologically encircle chromatin. The two HEAT-repat subunits associate with the Kleisin subunit.

Almost all organisms have condensin or condensin-like protein complexes. While prokaryotes and lower eukaryotes only have one isoform, two condensin isoforms often occur in multicellular organisms - condensin I and condensin II. Condensin II complexes are found in the nucleus during the entire cell cycle. Condensin I complexes are in the interphase in the cytoplasm and only come into contact with chromatin after the nuclear envelope has dissolved in mitosis .

The SMC subunits can bind ATP as a dimer . In vitro it has been shown that condensins can use the energy from ATP hydrolysis to bind DNA and twist it. The condensation of the DNA probably works the same way. In the process, some subunits of the condesin are phosphorylated by the M-cdk active during the M phase and form DNA loops through intramolecular cross-links.

Individual evidence

  1. ↑ T. Hirano: Condensins: universal organizers of chromosomes with various functions . In: Genes & Dev. . 2012, pp. 1659-1678. doi : 10.1101 / gad.194746.112 .
  2. ↑ S. Cuylen, J. Metz, C. Häring: Condensin structures chromosomal DNA through topological links . In: Nat Struct Mol Biol . 2011. doi : 10.1038 / nsmb.2087 .
  3. ↑ Bruce Alberts et al .: Molecular Biology of the Cell , 4th Edition, 2004, pp. 1196–1197.