Overexpression of Eaf1, a subunit of the NuA4 lysine acetyl transferase complex, rescues growth defects in the budding yeast H3K36M oncohistone model via histone H4 tail acetylation

Histone proteins are critical for regulating functions that occur at DNA, such as gene expression. Certain mutations in histone genes were characterized to drive oncogenesis, termed oncohistones, and one of the first identified oncohistones is H3K36M. While humans have a high copy number of H3 genes, making genetic engineering in cell lines challenging, budding yeast only have two H3 genes. Additionally, histone H3 shares 90% sequence identity between budding yeast and humans, making it a great model for studying H3K36M. We had previously identified the catalytic subunit of the NuA4 lysine acetyltransferase complex as a suppressor of growth defects in H3K36 mutant yeast cells. Here, we expand upon our initial finding by discovering that the NuA4 scaffold Eaf1 is an even stronger suppressor of mutant H3K36 growth defects. We uncover that this suppression by Eaf1 is dependent on its HSA domain. We also created H4-4K>A and H4-4K>R mutants that eliminated the potential for acetylation at mutant H4, on their own and in combination with H3K36 mutants, and found that these H4 mutants have reduced viability and disrupted global H4 acetylation. Importantly, we discover that Eaf1 is unable to suppress growth defects in these H4 mutants, suggesting its suppression is dependent on acetylation at histone H4 N-terminal tails. Lastly, we discovered that inhibiting NuA4 activity in H3K36M human cells limits their oncogenic potential. Together, this work further characterizes the connection between H3K36 and H4 N-terminal tails in the context of a cancer-causing mutation.