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Fig. 2 | Retrovirology

Fig. 2

From: Origin and functional role of antisense transcription in endogenous and exogenous retroviruses

Fig. 2

The HTLV-1 antisense gene, hbz. The figure shows a schematic representation of the HTLV-1 proviral genome with structural and enzymatic genes (gag, pol/pro, env), regulatory genes (tax and rex), and accessory genes (p12, p13, p30) expressed from the proviral 5’ LTR. The antisense gene hbz is expressed from the proviral 3’ LTRs in a manner independent of the viral transactivator, Tax. The hbz promoter contains binding sites for Sp1 and MEF-2. HTLV-1 produces spliced (s-hbz) and unspliced (us-hbz) antisense RNA variants, which encode two forms of the HBZ protein. Hbz transcripts have both noncoding and protein-coding activities. They act as lncRNAs that increase expression of Survivin and E2F1, which promote cell survival and proliferation, respectively. In addition, Hbz transcripts act as mRNAs that encode for the HBZ protein. HBZ interacts with CREB-2, it prevents the formation of the CREB-2/Tax heterodimer and binding to TRE sites in the HTLV-1 5’ LTR, and ultimately it downregulates HTLV-1 expression

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