Novel interactions between the HTLV antisense proteins HBZ and APH-2 and the NFAR protein family: Implications for the HTLV lifecycles

- This study demonstrates for the first time interactions between NF90/110 and the HTLV antisense proteins HBZ and APH-2.
- We show that NF90/110 significantly enhance LTR activation by the HTLV Tax protein, an effect that is abolished by HBZ but enhanced by APH-2.
- The study shows that even though the HTLV antisense proteins activate survivin expression they antagonize the ability of NF90/110 to do so.
- Overall we found that NF90/110 positively regulate HTLV infection and as such might represent a therapeutic target in infected cells.

The human T-cell leukaemia virus type 1 and type 2 (HTLV-1/HTLV-2) antisense proteins HBZ and APH-2 play key roles in the HTLV lifecycles and persistence in the host. Nuclear Factors Associated with double-stranded RNA (NFAR) proteins NF90/110 function in the lifecycles of several viruses and participate in host innate immunity against infection and oncogenesis. Using GST pulldown and co-immunoprecipitation assays we demonstrate specific novel interactions between HBZ/APH-2 and NF90/110 and characterised the protein domains involved. Moreover we show that NF90/110 significantly enhance Tax mediated LTR activation, an effect that was abolished by HBZ but enhanced by APH-2. Additionally we found that HBZ and APH-2 modulate the promoter activity of survivin and are capable of antagonising NF110-mediated survivin activation. Thus interactions between HTLV antisense proteins and the NFAR protein family have an overall positive impact on HTLV infection. Hence NFARs may represent potential therapeutic targets in HTLV infected cells.