Shugoshin 1

Shugoshin 1 or Shugoshin-like 1, is a protein that in humans is encoded by the SGO1 gene.

Mechanisms
A physical mechanism that guarantees the accurate segregation of sister chromatids during mitosis arises from the ring shaped cohesin complex consisting of 4 subunits (SMC1A/B, SMC3, SCC1, and SA1/2 in humans). This complex encircles the two sister chromatids and resists the pulling force of microtubules. The characteristic X-shape chromosomes are formed due to the centromeric cohesin protected by Shugoshin-PP2A complex.

Kinetochore localization of Sgo1-PP2A is dependent upon phosphorylation on histone H2A of nucleosome, which is the important substrate of spindle checkpoint kinase BUB1. Centromeric cohesin and H2A-pT120 specify two distinct pools of Sgo1-PP2A at inner centromeres and kinetochores respectively, while the CDK1/cyclin B phosphorylation on Sgo1 is essential for Sgo1-PP2A to protect centromeric cohesin, not only for bringing PP2A to cohesin, but also physically shield out the negative regulator WAPAL from cohesin.