Impact of dynamics of H2A variants on transcription

Gene expression in multicellular eukaryotes is regulated by histones, proteins that directly associate with DNA. Among the five families of histones, the H2A family contains variants that specifically occupy either expressed genes, repressed genes, or transposons. The regulatory mechanisms that control their specific patterns of deposition of H2A variants remains largely unknown. We have identified that the chromatin remodeler DDM1 is responsible for the deposition of the variant H2A.W on transposons in flowering plants. This chromatin remodeler and its ortholog in mammals were identified twenty years ago for their impact on transposon silencing and DNA methylation but their mechanism of action had remained unclear. This proposal will use a new genomic approach to determine whether the deposition of H2A.W by DDM1 is directly responsible for transposon silencing. We will use a combination of genetic and biochemical approaches to identify regulatory partners of DDM1. As histones and their associated chromatin remodelers in animals evolved in parallel with those in plants, this research will impact our understanding of chromatin dynamics in all eukaryotes.

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