Analysis of meiosis using ´shokat´ mutants

Meiosis is a specialized pathway that enables diploid organisms to reproduce sexually by generating haploid gametes in two successive divisions. Protein phosphorylation is known to play a key role in regulation of meiosis. We have recently constructed conditional alleles of almost all S. pombe protein kinases essential for cell growth. In this project, we want to use these conditional kinase mutants to identify those required for proper segregation of chromosomes during meiosis. Ultimately, we would like to elucidate the molecular mechanisms by which individual kinases regulate chromosome segregation during meiosis. This project will not only help us to understand meiosis, which is a fundamental and fascinating process, it may also have important implications for the fertility and human health. A fuller understanding of the causes and consequences of chromosome missegregation may enable us to understand the origins of human meiotic aneuploidy, the leading cause of miscariages and genetic disorders such as Down syndrome.

The two main aims of this project were 1) to identify and characterize protein kinases required for proper segregation of chromosomes during meiosis focusing on conditional analog-sensitive alleles of protein kinases essential for cell growth and 2) to develop the analog-sensitive allele of the Pat1 kinase as an improved tool to generate meiotic cultures with a high degree of synchrony. We discovered that the Nak1-Sog2 kinase complex interacts with the casein kinase 2 complex (Cka1, Ckb1 and Ckb2). Using live-cell imaging we observed that inhibition of the Ksg1 kinase leads to breakage of the meiosis I spindle. We showed that casein kinases Hhp1 and Hhp2 regulate meiotic recombination by phosphorylating Rec11. We developed a protocol for synchronized fission yeast meiosis using an ATP analog-sensitive Pat1 protein kinase. Importantly, this protocol eliminates detrimental effects of elevated temperature, which is required to inactivate the commonly used temperature-sensitive Pat1 kinase mutant. In addition to the aims mentioned above, we made several other important discoveries such as deciphering the role of Dbl2 protein in DNA damage repair. We presented our results at international conferences and published in important scientific journals such as PLoS Genetics. We believe that we made an important contribution to the field of chromosome biology and that our studies will inspire other scientists from various fields.