Sister chromatid cohesion and centromere organization in meiosis

Abstract

Meiosis is a unique cell cycle that allows halving of the chromosome number, a step essential for sexual reproduction. In meiosis, a single round of DNA replication is followed by two rounds of chromosome segregation that generate four haploid gametes from one diploid cell. To accomplish this specialized chromosome segregation, sister kinetochores are mono-oriented and attached to microtubules emanating from the same spindle pole (monopolar attachment) to segregate homologous chromosomes (rather than sister chromatids) in the first meiotic division (meiosis I). So far, two classes of proteins have been implicated in promoting mono-orientation: meiosis-specific cohesin containing Rec8 and meiosis I-specific kinetochore proteins. Another key regulation during meiosis-I involves the removal of sister chromatid cohesion along the arm region, while that around the centromere is retained, since the residual centromeric cohesion is responsible for the faithful segregation of sister kinetochores in the second division (meiosis II). A recently identified family of proteins called shugoshin, which associates with protein phosphatase 2A (PP2A), plays a critical role in the centromeric protection of cohesin at meiosis I. © 2007 Springer-Verlag Berlin Heidelberg.