Connecting the dots Delineating the regulation of H3K79 methylation by Dot1

This thesis describes several studies performed to increase our understanding of the regulation of an important histone modification, the methylation of histone H3 on lysine 79. This modification is concerved from yeast to humans, as is the enzyme that places it: Dot1 in yeast, DOT1L in mammals. DOT1L is important in development, reprogramming and cancer, yet on a molecular level H3K79 methylation is not well understood.
In the first chapters of this thesis, current literature will be reviewed on the regulation and function of H3K79 methylation, the crosstalk between aging and the epigenome, and the modeling studies that uncovered the distributive nature of H3K79 methylation by Dot1. In Chapter 4, we show that the crosstalk from H2B ubiquitination to methylation of H3K79 and H3K4 is remarkably flexible in vivo. In Chapter 5, we set out to discover new regulators of H3K79 methylation. To this end, we developed a novel and powerful screening technology that uses a barcoded genome-wide yeast knock-out collection. This technology, Epi-ID, was validated by the H3K79me regulator screen. Moreover, we identified several new players that could be validated. In Chapter 6, a specific hit from the Epi-ID screen was validated and its conservation in mice and relevance in a cancer context was investigated.
In conclusion, the work described in this thesis has identified several new Dot1 regulators and shows that Dot1 regulation is part of a highly-interconnected network of chromatin control.