| Summary: | The formation of chromatin defines when and where genes will be expressed, from the histone proteins forming the nucleosome and their many post-translational modifications, to the immense number of proteins that bind these modifications. This thesis is comprised of two projects: the first is an analysis of the essential plant homeodomain-containing protein called zinc finger protein 1 (ZFP-1); the second is a study into how RNA interference (RNAi) factors are involved in histone production in C. elegans. I investigate the physical and biological properties of the PHD fingers of ZFP-1 and find that 1) they are essential for viability and 2) they specifically bind to methylated lysine 4 on histone H3. This study has expanded our understanding of the molecular nature of ZFP-1, the C. elegans ortholog of AF10, which has a role in chromosomal translocations promoting leukemia. I also determine that the RNAi factors CSR-1, EGO-1 and DRH-3 are required for proper histone production in C. elegans. Severe histone depletion results from the knockdown of these RNAi pathway components, which explains both the phenotypes of sterility and chromosome segregation defects in early embryos that are associated with mutants of these factors. This discovery explains the well-known, but poorly understood, phenotypes of the RNAi mutants and provides the first evidence for RNAi positively affecting gene expression.
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