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Published August 27, 1999 | public
Journal Article

The tax protein-DNA interaction is essential for HTLV-I transactivation in vitro

Abstract

The human T-cell leukemia virus type-1 (HTLV-I)-encoded Tax protein enhances viral gene transcription through interaction with three repeated DNA elements located in the viral promoter. These elements, called viral CREs, are composed of an off-consensus eight base-pair cyclic AMP response element (CRE), immediately flanked by sequences that are rich in guanine and cytosine residues. Recent biochemical experiments have demonstrated that in the presence of the cellular protein CREB, Tax directly binds the viral CRE G+C-rich sequences via interaction with the minor groove. To determine the functional significance of the Tax-DNA interaction, we synthesized minor groove-binding pyrrole-imidazole polyamides which bind specifically to the G+C-rich sequences in the viral CREs. At concentrations where the polyamides specifically protect the G+C-rich sequences from MPE:Fe cleavage, the polyamides block the Tax-DNA interaction. At precisely these same concentrations, the polyamides specifically inhibit Tax transactivation in vitro, without altering CREB-activated transcription or basal transcription from the same promoter. Together, these data provide strong evidence that Tax-viral CRE interaction is essential for Tax function in vitro, and suggest that targeted disruption of the Tax-DNA minor groove interaction with polyamides may provide a novel approach for inhibiting viral replication in vivo.

Additional Information

© 1999 Academic Press. (Received 7 April 1999; received in revised form 9 June 1999; accepted 25 June 1999) We thank Holli Giebler for technical assistance, Dr Mark Anderson for the G-less cassette promoter templates, C.-Z. Giam and R. Harrod for the Tax point mutant expression plasmids and Joel Gottesfeld for numerous helpful discussions. This work was supported by NIH CA55035 (J.K.N.) and NIH GM51747 (P.B.D.), and a Colorado Institute for Research in Biotechnology (CIRB) fellowship for B.A.L.

Additional details

Created:
August 22, 2023
Modified:
October 18, 2023