Histone methyltransferase. Dimethylates 'Lys-36' of histone H3, a specific tag for epigenetic transcriptional activation. Plays a central role in early development and is responsible for all H3 'Lys-36' dimethylation until about the 40-cell stage. Indirectly involved in the global inactivation of the X chromosomes in germline cells, possibly by excluding the mes-2-mes-3-mes-6 repressive Polycomb complex from the autosomes (PubMed:12077420, PubMed:16968818). Not related to transcription elongation (PubMed:12077420, PubMed:16968818). Required for small-RNA-induced H3K27 trimethylation (PubMed:26365259). May suppress sensitivity to RNAi (PubMed:16507136). May regulate the expression of genes required for vulval development (PubMed:16507136, PubMed:16710447). L-lysyl(36)-[histone H3] + 2 S-adenosyl-L-methionine = 2 H(+) + N(6),N(6)-dimethyl-L-lysyl(36)-[histone H3] + 2 S-adenosyl-L-homocysteine Specifically associated with the autosomes and with the distal tip of chromosome X. Colocalizes with methylated 'Lys-4' of histone H3. In adults, it is predominantly expressed in the germline, and weakly expressed in intestinal cells. Expressed both maternally and zygotically. Expressed in all cells of early embryos. In late embryos and L1 larva, it is weakly expressed in somatic cells, while it is expressed at intermediate levels in the primordial germ cells Z2 and Z3. Derepression of X-linked genes in the germline. RNAi-mediated knockdown results in sterility (PubMed:16710447). RNAi-mediated knockdown suppresses the multivulval phenotype of the lin-15A/B n765 mutant (PubMed:16507136, PubMed:16710447). RNAi-mediated knockdown at 25 degrees Celsius rescues the larval lethality phenotype of the mep-1 (q660) single mutants (PubMed:16710447). Belongs to the class V-like SAM-binding methyltransferase superfamily. Histone-lysine methyltransferase family. SET2 subfamily.