May modulate chromatin structure by regulation of nucleosome assembly/disassembly (By similarity). Could function together with B-type cyclins in the regulation of microtubule dynamics. Can form homomeric and heteromeric protein complexes with NAP1;3. Binds histones H2A and H2B in vivo. Also able to bind histones H1 and H4 in vitro. Interacts with CYCB1;1 and with alpha tubulin. Highly expressed at the G1/S transition. The acidic domain is probably involved in the interaction with histones. Belongs to the nucleosome assembly protein (NAP) family.