6qbw

Structural highlights

Function

POL_HTLV2 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.[UniProtKB:P03345] Matrix protein.[UniProtKB:P03345] Forms the spherical core of the virus that encapsulates the genomic RNA-nucleocapsid complex.[UniProtKB:P03362] Binds strongly to viral nucleic acids and promote their aggregation. Also destabilizes the nucleic acids duplexes via highly structured zinc-binding motifs.[UniProtKB:P03345] 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 (Potential). Cleaves the translation initiation factor eIF4G leading to the inhibition of host cap-dependent translation (By similarity).[UniProtKB:P03362][PROSITE-ProRule:PRU00275] RT is a multifunctional enzyme that converts the viral RNA genome into dsDNA in the cytoplasm, shortly after virus entry into the cell. This enzyme displays a DNA polymerase activity that can copy either DNA or RNA templates, and a ribonuclease H (RNase H) activity that cleaves the RNA strand of RNA-DNA heteroduplexes in a partially processive 3' to 5'-endonucleasic mode. Conversion of viral genomic RNA into dsDNA requires many steps. A tRNA-Pro binds to the primer-binding site (PBS) situated at the 5'-end of the viral RNA. RT uses the 3' end of the tRNA primer to perform a short round of RNA-dependent minus-strand DNA synthesis. The reading proceeds through the U5 region and ends after the repeated (R) region which is present at both ends of viral RNA. The portion of the RNA-DNA heteroduplex is digested by the RNase H, resulting in a ssDNA product attached to the tRNA primer. This ssDNA/tRNA hybridizes with the identical R region situated at the 3' end of viral RNA. This template exchange, known as minus-strand DNA strong stop transfer, can be either intra- or intermolecular. RT uses the 3' end of this newly synthesized short ssDNA to perform the RNA-dependent minus-strand DNA synthesis of the whole template. RNase H digests the RNA template except for a polypurine tract (PPT) situated at the 5' end of the genome. It is not clear if both polymerase and RNase H activities are simultaneous. RNase H probably can proceed both in a polymerase-dependent (RNA cut into small fragments by the same RT performing DNA synthesis) and a polymerase-independent mode (cleavage of remaining RNA fragments by free RTs). Secondly, RT performs DNA-directed plus-strand DNA synthesis using the PPT that has not been removed by RNase H as primer. PPT and tRNA primers are then removed by RNase H. The 3' and 5' ssDNA PBS regions hybridize to form a circular dsDNA intermediate. Strand displacement synthesis by RT to the PBS and PPT ends produces a blunt ended, linear dsDNA copy of the viral genome that includes long terminal repeats (LTRs) at both ends (By similarity). Catalyzes viral DNA integration into the host chromosome, by performing a series of DNA cutting and joining reactions.^[1]

See Also

• Retroviral integrase 3D structures

References

1. ↑ Balakrishnan M, Zastrow D, Jonsson CB. Catalytic activities of the human T-cell leukemia virus type II integrase. Virology. 1996 May 1;219(1):77-86. PMID:8623556 doi:10.1006/viro.1996.0224
2. ↑ Barski MS, Minnell JJ, Hodakova Z, Pye VE, Nans A, Cherepanov P, Maertens GN. Cryo-EM structure of the deltaretroviral intasome in complex with the PP2A regulatory subunit B56gamma. Nat Commun. 2020 Oct 7;11(1):5043. doi: 10.1038/s41467-020-18874-y. PMID:33028863 doi:http://dx.doi.org/10.1038/s41467-020-18874-y