Loss of SET1/COMPASS methyltransferase activity reduces lifespan and fertility in Caenorhabditis elegans
Post-translational modification of histones, particularly lysine methylation, are thought to play a crucial role in the aging process. Histone 3 lysine 4 (H3K4) methylation, a modification associated with active chromatin, is mediated by a family of SET1 methyltransferases acting within conserved multiprotein complexes known as COMPASS. Previous work in model organisms with partial or complete deletion of COMPASS subunits has yielded conflicting results about the requirement for H3K4 methylation during aging. Here, we reassessed the role of SET1/COMPASS-dependent H3K4 methylation in Caenorhabditis elegans lifespan regulation and fertility by generating set-2(syb2085) mutant animals that express a catalytically inactive form of SET-2, the C. elegans homolog of SET1. We show that animals bearing catalytically inactive SET-2 retain the ability to form COMPASS complexes but have a marked global loss of H3K4 dimethylation and trimethylation. Consistent with previous work, reduced H3K4 methylation was accompanied by loss of fertility; however, in striking contrast to earlier studies, set-2(syb2085) mutants displayed a significantly shortened, not extended, lifespan and had normal intestinal fat stores. Furthermore, other commonly used set-2 mutants were also short-lived, as was a cfp-1 mutant that lacks a non-catalytic SET1/COMPASS component and displays reduced H3K4 methylation. These results challenge previously held views and establish that wild-type H3K4 methylation levels are necessary to achieve a normal lifespan in C. elegans.