The transcription-dependent dissociation of P-TEFb-HEXIM1-7SK RNA relies upon formation of hnRNP-7SK RNA complexes.
The positive transcription elongation factor P-TEFb controls the elongation of transcription by RNA polymerase II. P-TEFb is inactivated upon binding to HEXIM1 or HEXIM2 proteins associated with a noncoding RNA, 7SK. In response to the inhibition of transcription, 7SK RNA, as well as HEXIM proteins, is released by an unknown mechanism and P-TEFb is activated. New partners of 7SK RNA were searched for as potential players in this feedback process. A subset of heterogeneous ribonuclear proteins, hnRNPs Q and R and hnRNPs A1 and A2, were thus identified as major 7SK RNA-associated proteins. The degree of association of 7SK RNA with these hnRNPs increased when P-TEFb-HEXIM1-7SK was dissociated following the inhibition of transcription or HEXIM1 knockdown. This finding suggested that 7SK RNA shuttles from HEXIM1-P-TEFb complexes to hnRNPs. The transcription-dependent dissociation of P-TEFb-HEXIM1-7SK complexes was attenuated when both hnRNPs A1 and A2 were knocked down by small interfering RNA. As hnRNPs are known to interact transiently with RNA while it is synthesized, hnRNPs released from nascent transcripts may trap 7SK RNA and thereby contribute to the activation of P-TEFb.
Barrandon
Charlotte
C
UMR 8541 CNRS, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris Cedex 05, France.
Bonnet
François
F
Nguyen
Van Trung
VT
Labas
Valérie
V
Bensaude
Olivier
O
D006367:HeLa Cells; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances / Q000378:metabolism*; D008957:Models, Genetic; D042925:Positive Transcriptional Elongation Factor B / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D020733:RNA, Small Cytoplasmic / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018271:Signal Recognition Particle / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic
C115990:7SL RNA; C476123:HEXIM1 protein, human; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D046911:Macromolecular Substances; D020033:Protein Isoforms; D020733:RNA, Small Cytoplasmic; D016601:RNA-Binding Proteins; D018271:Signal Recognition Particle; D014157:Transcription Factors; D042925:Positive Transcriptional Elongation Factor B
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