May be involved in control of the cell cycle. Optimum temperature is 20 degrees Celsius for complex formation activity of the N-terminus and 33.5 degrees Celsius for nuclear localization of the protein in vitro. Core component of several methyltransferase-containing complexes. Component of the SET1 complex, composed at least of the catalytic subunit Set1, wds/WDR5, Wdr82, Rbbp5, ash2, Cfp1/CXXC1, hcf and Dpy-30L1. Component of the MLL3/4 complex composed at least of the catalytic subunit trr, ash2, Rbbp5, Dpy-30L1, wds, hcf, ptip, Pa1, Utx, Lpt and Ncoa6. Component of the Ada2a-containing (ATAC) complex composed of at least Ada2a, Atac1, Hcf, Ada3, Gcn5, Mocs2B, Charac-14, Atac3, Atac2, NC2beta and wds (PubMed:18327268). Expressed throughout development and in adults. Proteolytic cleavage occurs between amino acids 900 and 1100 within the non-conserved central region, giving rise to two independent but tightly associated N- and C-terminal subunits. Due to lack of HCF repeats, the cleavage process occurs via a different mechanism to that in the mammalian HCFC1. Exons 9 and 10 deleted. Exon 12 deleted. Truncated N-terminus.