Acetyltransferase that acetylates in vitro histones H2A and H3. Does not act as a transcriptional activator but might be involved in the sink-source transition. In case of begomoviruses infection, acetylates the capsid protein (CP), but not the nuclear shuttle protein (NSP). Required for begomovirus infection and systemic spread. Inhibited by the viral nuclear shuttle protein (NSP) that binds to the region required for oligomerization. Vmax:15.1 fmol/min/pmol enzyme. Oligomer. Interacts with begomoviruses NSP but not with CP. This interaction may allow NSP to recruit NSI monomers to acetylate viral genome-bound CP and thus regulate nuclear export of viral genome by NSP. Highly expressed in cauline leaves, at lower levels in stems, siliques, inflorescences and rosettes leaves and at very low levels in roots. Expressed in the xylem parenchyma and phloem of the leaves and root, and in guard cells of young leaves. Expressed in the apical meristem, root vasculature and all veins in the cotyledons of young developing seedlings. Loss of expression in the older maturing tissues. Autoacetylated. Lacks the bromodomain involved in binding of other acetyltransferases to histones. Belongs to the acetyltransferase family.