DNA methyltransferase that specifically methylates the promoters of evolutionarily young retrotransposons in the male germline (PubMed:27856912, PubMed:28854222). De novo methylation and subsequent repression of transposable elements prevents their mobilization, which is essential for germline integrity (PubMed:27856912, PubMed:28854222). a 2'-deoxycytidine in DNA + S-adenosyl-L-methionine = a 5-methyl-2'-deoxycytidine in DNA + H(+) + S-adenosyl-L-homocysteine Interacts with SPOCD1. Specifically expressed in testis. Expression peaks around 16.5 dpc, when de novo methylation takes place in male germline. Mice are viable and healthy but show male sterility due to defects in spermatogenesis (PubMed:27856912). Male mice show hypogonadism and azoospermia with interruption of spermatogenesis at the pachytene stage of meiosis I (PubMed:27856912). Retrotransposons are derepressed due to DNA demethylation (PubMed:27856912). Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family. Evolved via a duplication of Dnmt3B and was initially annotated as a pseudogene. Best left unsaid - Issue 207 of September 2018