Positive transcription elongation factor b (P-TEFb) contributes to dengue virus-stimulated induction of interleukin-8 (IL-8)

Dengue virus (DENV) is one of the most common infectious pathogens worldwide. One major clinical and pathogenic feature of DENV infection is the elevation of interleukin-8 (IL-8) expression; however, little is known about the molecular mechanism of DENV-induced chemokine production. The positive transcription elongation factor b (P-TEFb) composed of CDK9 and cyclin T1 stimulates gene expression by enhancing RNA polymerase II (RNA pol II) processivity. This study examined the possibility that P-TEFb mediates DENV-induced IL-8 expression. The treatment of either a pharmacological inhibitor of P-TEFb, 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) or cyclin T1 siRNA prior to DENV infection abolished the elevation of IL-8, indicating that P-TEFb is essential for IL-8 induction. Moreover, DENV core protein participated in the activation of IL-8 promoter in a P-TEFb-dependent manner. Immunostaining and co-immunoprecipitation assays demonstrated the association between P-TEFb and DENV core protein. Finally, chromatin immunoprecipitation (ChIP) results indicated that P-TEFb and DENV core protein were recruited to the transcriptionally active IL-8 gene promoter. Taken together, this study showed that P-TEFb and DENV core protein work in concert to enhance IL-8 gene expression by DENV infection. This is the first demonstration of P-TEFb being directly involved in virus-induced host gene expression by interacting with a viral structural protein.