アクティブボード・２０１５年　７月
　　　　　・・・・・２０１５年　７月　２日更新・・・・・
研究発表を行った学会；
・Cold Spring Harbor Retroviruses Meeting
　２０１５年５月１８日〜２３日（Cold Spring Harbor Laboratory, New York, USA）
タイトル；HIV-1 Vpr and p21WAF1 restrict the LINE-1 mobility.
発表者；有海　康雄　氏
　　　（熊本大学　国際先端医学機構　エイズ学研究センター　有海研究室）
Abstract；
Long interspersed nuclear element-1 (LINE-1, L1) is a non-LTR retrotransposon, encoding ORF1p with RNA binding domain and ORF2p with endonuclease and reverse transcriptase activities. Although L1 is a genetic mobile element composing about 17% of the human genome, whether L1 affects the infection and replication of HIV-1 is still unclear. Therefore, we investigated the cross talk of HIV-1 with L1.
For this, 293T cells were co-transfected with HIV-1 molecular clones (R9, NL4-3, JR-FL) and pL1RP-EGFP plasmid, which contains EGFP-retrotransposition detector cassette in the antisense orientation or pYX014 plasmid, which has the firefly luciferase-based retrotransposition detector cassette. The fluorescence of GFP can be detected by flow cytometer or the luciferase activity can be measured only when L1 retrotransposition has happened. Notably, L1 retrotransposition was suppressed by HIV-1 expression. Subsequently, we examined which HIV-1 protein suppresses L1 retrotransposition using each HIV-1 protein expressing plasmid. Consequently, overexpression of Vpr showed strong suppressive effect on the L1 retrotransposition. Moreover, HIV-1 infection could suppress L1 retrotransposition activity in CD4+ HeLa P4.2 cells.
On the other hand, we observed an incorporation of L1 ORF1p protein into HIV-1 virion. However, L1 ORF1p affected neither level of intracellular HIV-1 p24 nor the extracellular p24 in the culture supernatant, suggesting that L1 does not affect the HIV-1 replication. Since Vpr is known to regulate host cell cycle, we also examined the potential role of host cell cycle regulatory protein p21Waf1 on the L1 retrotoransposition efficiency. As expected, p21Waf1 markedly suppressed the L1 retrotransposition without inhibiting the L1 promoter activity. Interestingly, N-terminal domain of p21Waf1 but not the C-terminal domain efficiently suppressed it, indicating that N-terminal kinase inhibitory domain (KID) is required for this inhibitory effect. Accordingly, another similar host cell cycle regulator p27 with the KID strongly suppressed the L1 retrotransposition.
Altogether, viral and host cell cycle regulatory machinery might restrict the L1 mobility.