Abstract
The replication of many retroviruses is mediated by a transcriptional activator protein, Tat, which activates RNA polymerase II at the level of transcription elongation. Tat interacts with Cyclin T1 of the positive transcription-elongation factor P-TEFb to recruit the transactivation-response TAR RNA, which acts as a promoter element in the transcribed 5′ end of the viral long terminal repeat. Here we present the structure of the cyclin box domain of Cyclin T1 in complex with the Tat protein from the equine infectious anemia virus and its corresponding TAR RNA. The basic RNA-recognition motif of Tat adopts a helical structure whose flanking regions interact with a cyclin T–specific loop in the first cyclin box repeat. Together, both proteins coordinate the stem-loop structure of TAR. Our findings show that Tat binds to a surface on Cyclin T1 similar to where recognition motifs from substrate and inhibitor peptides were previously found to interact within Cdk–cyclin pairs.
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Acknowledgements
We thank D. Ludwig for expert technical assistance and P. Afonine for helpful discussions on the PHENIX program. Data collection was done at the European Synchrotron Radiation Facility, beamline ID23-1, Grenoble, France, and we thank the beamline staff for assistance. M.G. thanks R. S. Goody for discussions and continuous support. K.A. was funded previously by the European Molecular Biology Organization and at present by a Marie-Curie fellowship. This work was supported by a grant from the Deutsche Forschungsgemeinschaft to M.G. (GE 976/5).
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K.A. crystallized the CycT1–Tat–TAR complex and solved the structure; A.S. purified the proteins and performed biochemical characterizations; K.V.B. made RNA transcripts and gel shift assays; K.S. and M.G. assisted K.A. throughout structure determination; M.G. supervised the study, designed all constructs and wrote the paper. All authors discussed the results and commented on the manuscript.
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Anand, K., Schulte, A., Vogel-Bachmayr, K. et al. Structural insights into the Cyclin T1–Tat–TAR RNA transcription activation complex from EIAV. Nat Struct Mol Biol 15, 1287–1292 (2008). https://doi.org/10.1038/nsmb.1513
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DOI: https://doi.org/10.1038/nsmb.1513
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