Changes in histone post-translational modifications are associated with aging through poorly defined mechanisms. Histone 3 lysine 4 (H3K4) methylation at promoters is deposited by SET1 family methyltransferases acting within conserved multiprotein complexes known as COMPASS. Using co-immunopurification coupled to mass spectrometry-based proteomics, we characterized complex members and binding partners in various genetic contexts, using WDR-5 or CFP-1 proteins as baits.