p30II is a multifunctional regulator that sequesters EP300/CREBBP and down-regulates CREB-responsive element (CRE) and Tax-responsive element (TRE) mediated transcription. Specifically binds and represses tax/rex mRNA nuclear export. Since Tax and Rex are positive regulators of viral gene expression, their inhibition by p30II reduces virion production, and allows the virus to escape the host immune surveillance and persist latently in an immune-competent host. p13II increases mitochondrial permeability to monovalent cations, producing a rapid, membrane potential-dependent influx of potassium. This could involve a channel-forming activity. Interferes with cell proliferation and transformation and promotes apoptosis induced by ceramide and Fas ligand, probably using the Ras signaling. p30II binds to the KIX domains of CREBBP and EP300. HTLV-1 lineages are divided in four clades, A (Cosmopolitan), B (Central African group), C (Melanesian group) and D (New Central African group). Belongs to the HTLV-1 accessory protein p30II family.