Monopolin is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

complex that in budding yeast is composed of the four proteins

CSM1 CSM1 (RNA name: Csm1p) is a protein that in Saccharomyces cerevisiae strain S288c is encoded by the CSM1 gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." ...

, HRR25, LRS4, and MAM1. Monopolin is required for the segregation of homologous

centromere The centromere links a pair of sister chromatids together during cell division. This constricted region of chromosome connects the sister chromatids, creating a short arm (p) and a long arm (q) on the chromatids. During mitosis, spindle fibers ...

s to opposite poles of a dividing cell during anaphase I of meiosis. This occurs by bridging

DSN1 DSN1, MIND kinetochore complex component, homolog (S. cerevisiae), also known as DSN1 or MIS13, is a protein which in humans encoded by the ''DSN1'' gene. Function DSN1 along with MIS12, DC8, PMF1, CBX5, ZWINT is a component of the kinetocho ...

kinetochore proteins to sister kinetochores within the centromere to physically fuse them and allow for the microtubules to pull each homolog toward opposite mitotic spindles.

Molecular structure

Monopolin is composed of a 4 CSM1:2 LRS4 complex which forms a V-shaped structure with two globular heads at the ends, which are responsible for directly crosslinking sister kinetochores. Bound to each CSM1 head is a MAM1 protein which recruits one copy of the HRR25 kinase. The hydrophobic cavity on the CSM1 subunit allows the hydrophobic regions of Monopolin receptor and kinetochore protein,

, to bind to and fuse the sister kinetochores.

Microtubules Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 a ...

can then attach to the kinetochores on the homologous centromeres and pull them toward opposite mitotic spindles to complete anaphase of meiosis I.

References

Proteins Molecular biology Protein complexes {{Protein-stub