Seems to function as a Vpr-like protein, since it mediates host cell cycle arrest in G2 phase. Cell cycle arrest creates a favorable environment for maximizing viral expression and production (By similarity). Was first thought to be the equivalent of lentiviral Tat protein, but it does not induce any transactivation of viral LTR promoter, or if any, at very low rate. The LTR promoter of this virus has a high basal activity and does apparently not need transactivation by a Tat-like protein.