H3K36ac is an epigenetic modification to the DNA packaging protein Histone H3. It is a mark that indicates the acetylation at the 36th lysine residue of the histone H3 protein. H3K36ac has not been widely studied but it is very widely conserved across mammals and yeast and marks genes. Specifically, it marks promoters of RNA polymerase II-transcribed genes which is opposite of H3K36me3.