HETERO-EVO · Reconstructing the origin and functional diversification of eukaryotic heterochromatin

Chromatin functionally organizes all eukaryotic genomes. Genomic regions within heterochromatin are transcriptionally repressed and aberrant expression can be lethal. Heterochromatin is characterized by specific histone modifications, but reader-repressor proteins are directly responsible for preventing DNA-templated processes. Recent studies suggest immense functional diversity of reader-repressor proteins that remains poorly understood. Understanding this diversity will reveal the ancestral composition and capabilities of eukaryotic heterochromatin and uncover unique heterochromatic systems. While exploring heterochromatin in species across the eukaryotic tree of life is key, most lineages have not been investigated due to complications with chromatin isolation, culturing, and genetic manipulation. To address these fundamental biological questions and overcome technical barriers, I will use a recently developed mass spectrometry method to identify proteins associated with known heterochromatic modifications in 19 species cultured in the Sebé-Pedrós laboratory representing all major and several early-branching eukaryotic lineages. To overcome genetic manipulation limitations, I will create a synthetic platform to heterologously assess reader-repressor functions of proteins in budding yeast. I will use this system to functionally characterize new regulators of heterochromatin from diverse eukaryotes. Finally, I will integrate these and other genomic data in a comparative framework to reconstruct the ancestral composition and evolutionary diversification of eukaryotic heterochromatin. Overall, my project will comprehensively identify the functional conservation and diversity of eukaryotic heterochromatin and create a powerful genetic tool to further explore chromatin function and evolution.