The function and regulation of the C. elegans Haspin histone kinase homolog, HASP-1

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Project Summary/Abstract The process of passing on chromosomes when cells divide must be carefully monitored because errors cause birth defects and infertility and are a hallmark of cancer. Cells use a variety of mechanisms to monitor the process of chromosome segregation and these mechanisms are often the target of drugs being developed in the hopes of finding chemotherapeutics that will kill cancer cells while having low toxicity to normal cells. The Chromosomal Passenger Complex (CPC) is a protein complex that monitors chromosome segregation. To provide its essential functions, the CPC must be recruited onto chromosomes at the right place and time. The mechanisms that target the CPC to chromosomes are not fully understood, but two key pathways have been discovered that rely on the activity of the protein kinases Haspin and Bub1. While the kinase Bub1 has been well studied since its discovery as part of the mitotic checkpoint signal, Haspin is a newly discovered kinase and fundamental questions abouts its function and regulation have not yet been answered. Better understanding Haspin’s function is critical because chemotherapy drugs targeting Haspin have shown promise. Haspin has features that make its inhibitors less likely to produce side effects, and multiple inhibitors have recently shown efficacy against a variety of cancer models and low toxicity to normal cells. Investigations into Haspin’s function have so far been limited to a small number of cell types undergoing mitosis in cell culture, which offers only a partial understanding of this molecule’s function. This proposal develops a new system to study Haspin function in a variety of cell types in vivo using the model organism C. elegans, which features powerful genetic and cell biological tools. Conditional knockdown of the C. elegans Haspin protein, HASP-1, combined with specific mutations in HASP-1 and associated proteins using CRISPR gene editing, will enable us to accomplish the following Specific Aims: 1) Determine the relative contribution of the Haspin and Bub1 pathways to CPC recruitment in different cell types in C. elegans, 2) Identify the mechanism by which HASP-1 is recruited to chromosomes, and 3) Determine the mechanisms by which HASP-1 becomes activated during mitosis and meiosis. Our experimental system allows us to address these Specific Aims in multiple cell types and in meiosis, a specialized cell division where these types of mechanistic studies are typically not possible in other animal systems. The proposed work will provide new insights into the molecular mechanisms underlying the function of this important cell cycle regulator, which will positively impact human health, especially as Haspin inhibitors show up more in clinical use. Proposed experiments will be performed in close collaboration with undergraduate researchers and a post-baccalaureate researcher, enhancing the research capacity of our institution and training the next generation of biomedical scientists.