Figure 5.

Cartoon of the working Model proposed for the interplay of IN-CTD, Tat and TAR during the early stage of HIV-1 proviral transcription. Once the integration has taken place, IN interacts with nascent TAR transcript through its CTD, directly interacting with the major groove and the hexaloop, thanks to its C-terminal tail. This binding induces TAR conformational changes, which promote the interaction of Tat with its substrate. Afterwards, Tat displaces IN-CTD from TAR and recruits the SEC complex in order to boost Pol II transcription.