Dynamic remodelling of human 7SK snRNP controls the nuclear level of active P-TEFb.
The 7SK small nuclear RNA (snRNA) regulates RNA polymerase II transcription elongation by controlling the protein kinase activity of the positive transcription elongation factor b (P-TEFb). In cooperation with HEXIM1, the 7SK snRNA sequesters P-TEFb into the kinase-inactive 7SK/HEXIM1/P-TEFb small nuclear ribonucleoprotein (snRNP), and thereby, controls the nuclear level of active P-TEFb. Here, we report that a fraction of HeLa 7SK snRNA that is not involved in 7SK/HEXIM1/P-TEFb formation, specifically interacts with RNA helicase A (RHA), heterogeneous nuclear ribonucleoprotein A1 (hnRNP), A2/B1, R and Q proteins. Inhibition of cellular transcription induces disassembly of 7SK/HEXIM1/P-TEFb and at the same time, increases the level of 7SK snRNPs containing RHA, hnRNP A1, A2/B1, R and Q. Removal of transcription inhibitors restores the original levels of the 7SK/HEXIM1/P-TEFb and '7SK/hnRNP' complexes. 7SK/HEXIM1/P-TEFb snRNPs containing mutant 7SK RNAs lacking the capacity for binding hnRNP A1, A2, R and Q are resistant to stress-induced disassembly, indicating that recruitment of the novel 7SK snRNP proteins is essential for disruption of 7SK/HEXIM1/P-TEFb. Thus, we propose that the nuclear level of active P-TEFb is controlled by dynamic and reversible remodelling of 7SK snRNP.
Van Herreweghe
Elodie
E
Laboratoire de Biologie Moléculaire Eucaryote, UMR5099, CNRS-Université Paul Sabatier, Toulouse, France.
Egloff
Sylvain
S
Goiffon
Isabelle
I
Jády
Beáta E
BE
Froment
Carine
C
Monsarrat
Bernard
B
Kiss
Tamás
T
D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D002846:Chromatography, Affinity; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D042925:Positive Transcriptional Elongation Factor B / Q000378:metabolism*; D011485:Protein Binding; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D017411:Ribonucleoproteins, Small Nuclear; D012313:RNA; D042925:Positive Transcriptional Elongation Factor B