Structural studies on the RNA-recognition motif of NELF E, a cellular negative transcription elongation factor involved in the regulation of HIV transcription
Résumé
The elongation of transcription of HIV RNA at the transactivation response element TAR is highly regulated by positive and negative factors. The cellular negative transcription elongation factor NELF was suggested to be involved in transcriptional regulation of human immunodeficiency virus type 1 (HIV-1) by binding to the stem of the viral TAR RNA which is synthesized by cellular RNA polymerase II at the viral long terminal repeat. NELF is a heterotetrameric protein consisting of NELF A, B, C or the splice variant D, and E. Here we determined the solution structure of the RNA recognition motif (RRM) of the RNA binding subunit NELF E and studied its interaction with the viral TAR RNA. Our data show that the separately expressed recombinant NELF E RRM owns {alpha}-helical and {beta}-strand elements adopting a {beta}{alpha}{beta}{beta}{alpha}{beta} fold and is able to bind to TAR RNA. Fluorescence equilibrium titrations with fluorescently labeled double and single stranded oligoribonucleotides representing the TAR RNA stem imply that NELF E RRM binds to the single stranded TAR RNAs with K D}-values in the low {mu}M range.
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