Figure 2.

Schematic figure of mechanisms regulating HTLV-1 provirus, in vitro and in vivo. (A) Schematic figure of HTLV-1 provirus in vitro or during the initial phase of infection in vivo. Tax and viral structural proteins can be expressed, because there is little immune surveillance against the viral antigens. (B) Schematic figure of HTLV-1 provirus during the chronic phase of infection in vivo. HTLV-1 maintains a distinct transcription pattern between 5′ long terminal repeat (LTR) and 3′-LTR by recruiting the host insulator protein CTCF. The insulator region of HTLV-1 provirus is thought to prevent the spread of heterochromatin from 5′-LTR to 3′-LTR. This could also induce chromatin looping with the host’s CTCF-binding sites.