Enables DNA binding activity; histone methyltransferase activity (H3-K9 specific); and promoter-specific chromatin binding activity. Involved in negative regulation of single stranded viral RNA replication via double stranded DNA intermediate and positive regulation of DNA methylation-dependent heterochromatin assembly. Acts upstream of or within several processes, including histone H3-K9 trimethylation; inner cell mass cell proliferation; and negative regulation of transcription by RNA polymerase II. Located in nucleus. Is expressed in several structures, including 1-cell stage embryo; central nervous system; long bone; oocyte; and white fat. Human ortholog(s) of this gene implicated in autistic disorder and lung cancer. Orthologous to human SETDB1 (SET domain bifurcated histone lysine methyltransferase 1). [provided by Alliance of Genome Resources, Apr 2022]