Increased association of 7SK snRNA with Tat cofactor P-TEFb following activation of peripheral blood lymphocytes.
OBJECTIVE
This study was undertaken to determine whether 7SK small nuclear RNA (snRNA), which has been proposed to function as an inhibitor of Tat cofactor P-TEFb, plays a role in transcriptional latency in T cells.


METHODS
The association of 7SK snRNA with P-TEFb was investigated in resting and activated peripheral blood lymphocytes (PBLs). Primary PBLs were isolated by standard methods and activated with phytohemagglutinin (PHA). Levels of 7SK snRNA were determined by Northern blotting and levels of the P-TEFb subunits cyclin-dependent kinase 9 and cyclin T1 were analyzed by immunoblotting.


RESULTS
The association of 7SK snRNA with P-TEFb complexes was specific. Following activation of PBLs, the levels of 7SK snRNA increased in a manner similar to U1 and U6 snRNA, sn RNAs involved in positive aspects of cellular gene expression. Unexpectedly, the association of 7SK snRNA with P-TEFb increased dramatically following lymphocyte activation.


CONCLUSIONS
Increased association of 7SK snRNA with P-TEFb in activated lymphocytes correlates with increased global transcription. This suggests that 7SK snRNA is unlikely to promote transcriptional latency in lymphocytes through an association with P-TEFb; it also suggests that the proposal that the association of 7SK snRNA with P-TEFb acts to inhibit transcriptional elongation needs to be re-evaluated.
Haaland
Richard E
RE
Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030, USA.
Herrmann
Christine H
CH
Rice
Andrew P
AP
D015152:Blotting, Northern / Q000379:methods; D056906:Cyclin T; D042863:Cyclin-Dependent Kinase 9 / Q000276:immunology; D016213:Cyclins / Q000276:immunology; D006367:HeLa Cells; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D042925:Positive Transcriptional Elongation Factor B / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000276:immunology; D011233:Precipitin Tests; D012342:RNA, Small Nuclear / Q000235:genetics* / Q000276:immunology; D012995:Solubility; D013601:T-Lymphocytes / Q000276:immunology / Q000502:physiology*; D014158:Transcription, Genetic
C503684:CCNT1 protein, human; D056906:Cyclin T; D016213:Cyclins; D012342:RNA, Small Nuclear; D042925:Positive Transcriptional Elongation Factor B; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9