Catalytic component of the histone acetyltransferase NuA3 complex, that acetylates Lys-14 of histone H3. Recruitment of NuA3 to nucleosomes requires methylated histone H3. In conjunction with the FACT complex, NuA3 may be involved in transcriptional regulation. In vitro, SAS3 acetylates free histones H3 and H4. It is involved in silencing the HMR locus. acetyl-CoA + L-lysyl-[protein] = CoA + H(+) + N(6)-acetyl-L-lysyl-[protein] Component of the NuA3 complex, composed of at least NTO1, SAS3, TAF14, YNG1 and EAF6. SAS3 interacts with CDC68/SPT16. Autoacetylation at Lys-367 is required for proper function. Belongs to the MYST (SAS/MOZ) family.