dimerization/docking (D/D) domain found in the DPY30/SDC1 family
This family includes DPY30 from animals and its homologs, including SDC1 from yeast. DPY30, also called dumpy-30, was initially discovered in Caenorhabditis elegans as a key player in X chromosome dosage compensation. Human DPY30 plays a dual function in moderately allosterically regulating the methyltransferase activity of SET1/COMPASS (COMplex of Proteins ASsociated with Set1) enzymes and contributing to the recruitment of the complex to chromatin. DPY30 is the core component of several methyltransferase-containing complexes including MLL1/MLL, MLL2/3 (also named ASCOM complex) and MLL4/WBP7. As part of the MLL1/MLL complex, DPY30 is involved in the methylation of histone H3 at 'Lys-4', particularly trimethylation. Histone H3 'Lys-4' methylation represents a specific tag for epigenetic transcriptional activation. In a teratocarcinoma cell, DPY30 plays a crucial role in retinoic acid-induced differentiation along the neural lineage, regulating gene induction and H3 'Lys-4' methylation at key developmental loci. It may also play an indirect or direct role in endosomal transport. Yeast SDC1, also called complex proteins associated with SET1 (COMPASS) protein SDC1, Set1C component SDC1, or suppressor of CDC25 protein 1, is the smallest subunit of COMPASS and interacts exclusively with Bre2 at the distal end of the catalytic module. It positively regulates the COMPASS catalytic module by stabilizing the non-canonical Bre2 SPRY domain. The COMPASS (Set1C) complex specifically mono-, di- and trimethylates histone H3 to form H3K4me1/2/3, which subsequently activates gene expression by regulating transcription elongation and plays a role in telomere length maintenance. This model corresponds to the C-terminal helical bundle domain of DPY30/SDC1, which is called dimerization/docking (D/D) domain. It forms a homodimer, which directly interacts with the Ash2L (Bre2 in yeast) subunit of COMPASS through its DPY30-binding motif (DBM).
Jiyao W et al.(2023). "The conserved domain database in 2023.",