HIV-1 TAR RNA enhances the interaction between Tat and cyclin T1.
Human immunodeficiency virus, type 1 (HIV-1), Tat activates elongation of RNA polymerase II transcription at the HIV-1 promoter through interaction with the cyclin T1 (CycT1) subunit of the positive transcription elongation factor complex, P-TEFb. Binding of Tat to CycT1 induces cooperative binding of the P-TEFb complex onto nascent HIV-1 TAR RNA. Here the specific interaction between Tat protein, human cyclin T1, and HIV-1 TAR RNA was analyzed by fluorescence resonance energy transfer, using fluorescein-labeled TAR RNA and a rhodamine-labeled Tat protein synthesized through solid-phase chemistry. We find that CycT1 remodels the structure of Tat to enhance its affinity for TAR RNA and that TAR RNA further enhances the interaction between Tat and CycT1. We conclude that TAR RNA nucleates the formation of the Tat.P-TEFb complex through an induced fit mechanism.
Zhang
J
J
Department of Pharmacology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
Tamilarasu
N
N
Hwang
S
S
Garber
M E
ME
Huq
I
I
Jones
K A
KA
Rana
T M
TM
D001483:Base Sequence; D056906:Cyclin T; D016213:Cyclins / Q000378:metabolism*; D005456:Fluorescent Dyes; D015696:Gene Products, tat / Q000378:metabolism*; D016325:HIV Long Terminal Repeat / Q000235:genetics*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D012367:RNA, Viral / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D054322:tat Gene Products, Human Immunodeficiency Virus
C503684:CCNT1 protein, human; D056906:Cyclin T; D016213:Cyclins; D005456:Fluorescent Dyes; D015696:Gene Products, tat; D012367:RNA, Viral; D054322:tat Gene Products, Human Immunodeficiency Virus