THE MEIOSIS SPECIFIC AAA+ ATPASE PCH2 INTERACTS WITH THE SYNAPTONEMAL COMPLEX PROTEIN HOP1 THROUGH THE HOP1 HORMA DOMAIN

Abstract

In most sexually reproducing organisms physical linkages are required between homologous chromosome pairs in order to properly segregate them in the first meiotic division. Crossovers (CO) provide this physical linkage and help to position chromosomes at the metaphase plate for association with the meiotic spindle, which segregates the homologs. A multi-protein complex known as the synaptonemal complex (SC) facilitates homology pairing and CO formation. Defects in SC assembly or CO formation result in non-disjunction of homologs leading to aneuploid gametes, and for the budding yeast S. cerevisiae, decreased spore viability. The meiosis specific AAA+ (ATPases Associated with diverse cellular Activities) ATPase Pch2 (Pachytene checkpoint) facilitates proper SC assembly by regulating the localization of the axial SC element Hop1. This helps ensures that each homolog pair produces at least one CO and is subsequently properly distributed to each daughter cell. Little is known about the mechanism by which Pch2 performs this function. The research presented here establishes reliable methods for purification of Hop1 and Pch2 for in vitro analysis. I also show that Pch2 is able to dissociate Hop1 from DNA in vitro when in the presence of ATP. By constructing and purifying a Hop1 mutant allele (Hop1-HORMA∆) I found that the N-Terminal HORMA protein-protein interaction domain of Hop1 is necessary for Pch2 interaction in vitro.