Chromatin regulator required for brain development: acts as a regulator of RNA elongation rate, thereby regulating neural stem cell (NSC) proliferation and synaptic transmission. May act by mediating trimethylation of 'Lys-36' of histone H3 (H3K36me3), which is essential to allow on-time RNA elongation dynamics. Also monomethylates 'Lys-9' of histone H3 (H3K9me1) in vitro. The relevance of histone methyltransferase activity is however subject to discussion. . This is the function of ENSG00000168137 (SETD5, SET domain containing 5).