MAQ1 and 7SK RNA interact with CDK9/cyclin T complexes in a transcription-dependent manner.
Positive transcription elongation factor b (P-TEFb) comprises a cyclin (T1 or T2) and a kinase, cyclin-dependent kinase 9 (CDK9), which phosphorylates the carboxyl-terminal domain of RNA polymerase II. P-TEFb is essential for transcriptional elongation in human cells. A highly specific interaction among cyclin T1, the viral protein Tat, and the transactivation response (TAR) element RNA determines the productive transcription of the human immunodeficiency virus genome. In growing HeLa cells, half of P-TEFb is kinase inactive and binds to the 7SK small nuclear RNA. We now report on a novel protein termed MAQ1 (for ménage à quatre) that is also present in this complex. Since 7SK RNA is required for MAQ1 to associate with P-TEFb, a structural role for 7SK RNA is proposed. Inhibition of transcription results in the release of both MAQ1 and 7SK RNA from P-TEFb. Thus, MAQ1 cooperates with 7SK RNA to form a novel type of CDK inhibitor. According to yeast two-hybrid analysis and immunoprecipitations from extracts of transfected cells, MAQ1 binds directly to the N-terminal cyclin homology region of cyclins T1 and T2. Since Tat also binds to this cyclin T1 N-terminal domain and since the association between 7SK RNA/MAQ1 and P-TEFb competes with the binding of Tat to cyclin T1, we speculate that the TAR RNA/Tat lentivirus system has evolved to subvert the cellular 7SK RNA/MAQ1 system.
Michels
Annemieke A
AA
UMR 8541 CNRS, Ecole Normale Supérieure, Laboratoire de Régulation de l'Expression Génétique, 75230 Paris Cedex 05, France.
Nguyen
Van Trung
VT
Fraldi
Alessandro
A
Labas
Valérie
V
Edwards
Mia
M
Bonnet
François
F
Lania
Luigi
L
Bensaude
Olivier
O
D000595:Amino Acid Sequence; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D056906:Cyclin T; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism; D016325:HIV Long Terminal Repeat / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D042925:Positive Transcriptional Elongation Factor B; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D014158:Transcription, Genetic; D014162:Transfection; D020798:Two-Hybrid System Techniques
C503684:CCNT1 protein, human; C441622:CCNT2 protein, human; D056906:Cyclin T; D016213:Cyclins; D015696:Gene Products, tat; C476123:HEXIM1 protein, human; D046911:Macromolecular Substances; D021122:Protein Subunits; D012342:RNA, Small Nuclear; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D042925:Positive Transcriptional Elongation Factor B; D017346:Protein Serine-Threonine Kinases; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases