Internal transcriptional regulatory elements in HIV-1 and other retroviruses.

The transcriptional regulation of retroviruses plays an important role in their pathogenesis. Cis-acting elements have been identified in the long terminal repeat (LTR) at the 5' extremity of the integrated provirus. These elements determine the rate and the site of transcription initiation and consist of arrays of binding sites for transcription factors. Recent studies have demonstrated the presence of additional regulatory elements, located outside of the LTR, within the transcribed region of several retroviruses including avian and murine retroviruses, HIV-1, HTLV-1 and the human spumaretroviruses. This review describes these new observations and analyzes their significance both in terms of retroviral transcriptional regulation and in terms of pathogenesis.