The matrix domain targets Gag, Gag-Pro and Gag-Pro-Pol polyproteins to the plasma membrane via a multipartite membrane binding signal, that includes its myristoylated N-terminus. Matrix protein. Forms the spherical core of the virus that encapsulates the genomic RNA-nucleocapsid complex. Binds strongly to viral nucleic acids and promote their aggregation. Also destabilizes the nucleic acids duplexes via highly structured zinc-binding motifs. The aspartyl protease mediates proteolytic cleavages of Gag and Gag-Pol polyproteins during or shortly after the release of the virion from the plasma membrane. Cleavages take place as an ordered, step-wise cascade to yield mature proteins. This process is called maturation. Displays maximal activity during the budding process just prior to particle release from the cell. Cleaves the translation initiation factor eIF4G leading to the inhibition of host cap-dependent translation. Homodimer; the homodimers are part of the immature particles. Interacts with human TSG101 and NEDD4; these interactions are essential for budding and release of viral particles. Homodimer; further assembles as homohexamers. This strategy of translation probably allows the virus to modulate the quantity of each viral protein. The capsid protein N-terminus seems to be involved in Gag-Gag interactions. Late-budding domains (L domains) are short sequence motifs essential for viral particle release. They can occur individually or in close proximity within structural proteins. They interacts with sorting cellular proteins of the multivesicular body (MVB) pathway. Most of these proteins are class E vacuolar protein sorting factors belonging to ESCRT-I, ESCRT-II or ESCRT-III complexes. Matrix protein p19 contains two L domains: a PTAP/PSAP motif which interacts with the UEV domain of TSG101, and a PPXY motif which binds to the WW domains of the ubiquitin ligase NEDD4. Specific enzymatic cleavages by the viral protease yield mature proteins. The polyprotein is cleaved during and after budding, this process is termed maturation. The protease is autoproteolytically processed at its N- and C-termini. Phosphorylation of the matrix protein p19 by MAPK1 seems to play a role in budding. Myristoylated (PubMed:11333909). Myristoylation of the matrix (MA) domain mediates the transport and binding of Gag polyproteins to the host plasma membrane and is required for the assembly of viral particles (By similarity). HTLV-1 lineages are divided in four clades, A (Cosmopolitan), B (Central African group), C (Melanesian group) and D (New Central African group). Produced by -1 ribosomal frameshifting at the gag-pro genes boundary.