Fig. 4
From: Retroviral PBS-segment sequence and structure: Orchestrating early and late replication events
PBS-segment is necessary for m7-G-Cap epigenetic modification and biphasic translation. Completely processed HIV-1 transcripts exhibit m7G-Cap and undergo canonical CBC exchange to eIF4E. Tat, Rev, Nef mRNA translation is promptly attenuated by eIF4E inactivation by hypo phosphorylated 4EBPs. The m7G-Cap of HIV-1 Rev/RRE-dependent intron-containing transcripts are subject to hyper methylation by TGS1 in a process that requires PBS-segment and host RHA/DHX9. TMG-Cap license specialized translation that is unaffected by the eIF4E inactivation. B. Downregulation of TGS1 or RHA, or introduced mutation on the PBS-segment abolished TMG-Cap on HIV-1 mRNAs and led to mTOR-dependent translation of virion proteins. C. Ab initio model of PBS-segment (top) and PBS-A140C (bottom) derived from SAXS data are shown