Positive transcription elongation factor (P-TEFb) is a heterodimer composed of cyclin T proteins and CDK9. P-TEFb plays a critical role in the transition of the RNA polymerase II (RNAPII) machinery from transcription initiation to elongation. At some genes during transcription initiation, RNAPII moves approximately 50 nucleotides away from the transcription start site into the gene where it then pauses and awaits signaling for the formation of a productive transcription elongation complex. The release of this promoter proximal pausing of RNAPII is signaled by phosphorylation of the C-terminal domain (CTD) within the largest subunit of RNAPII at Ser2 of the heptapeptide repeat sequence by P-TEFb. This phosphorylation event is important for the recruitment of mRNA processing factors and chromatin modifiers that are necessary for proper gene expression. P-TEFb also promotes transcription elongation by phosphorylating DSIF (DRB-induced stimulating factor) and NELF (negative elongation factor), two negative elongation factors that retain RNAPII at the promoter proximal region of genes to initiate transcription elongation.
Positive transcription elongation factor (P-TEFb) is a heterodimer composed of cyclin T proteins and CDK9. P-TEFb plays a critical role in the transition of the RNA polymerase II (RNAPII) machinery from transcription initiation to elongation. At some genes during transcription initiation, RNAPII moves approximately 50 nucleotides away from the transcription start site into the gene where it then pauses and awaits signaling for the formation of a productive transcription elongation complex. The release of this promoter proximal pausing of RNAPII is signaled by phosphorylation of the C-terminal domain (CTD) within the largest subunit of RNAPII at Ser2 of the heptapeptide repeat sequence by P-TEFb. This phosphorylation event is important for the recruitment of mRNA processing factors and chromatin modifiers that are necessary for proper gene expression. P-TEFb also promotes transcription elongation by phosphorylating DSIF (DRB-induced stimulating factor) and NELF (negative elongation factor), two negative elongation factors that retain RNAPII at the promoter proximal region of genes to initiate transcription elongation.
This protein belongs to the highly conserved cyclin family, whose members are characterized by a dramatic periodicity in protein abundance through the cell cycle. Cyclins function as regulators of CDK kinases. Different cyclins exhibit distinct expression and degradation patterns which contribute to the temporal coordination of each mitotic event. This cyclin tightly associates with CDK9 kinase, and was found to be a major subunit of the transcription elongation factor p-TEFb. The kinase complex containing this cyclin and the elongation factor can interact with, and act as a cofactor of human immunodeficiency virus type 1 (HIV-1) Tat protein, and was shown to be both necessary and sufficient for full activation of viral transcription. This cyclin and its kinase partner were also found to be involved in the phosphorylation and regulation of the carboxy-terminal domain (CTD) of the largest RNA polymerase II subunit.
Regulatory subunit of the cyclin-dependent kinase pair (CDK9/cyclin-T1) complex, also called positive transcription elongation factor B (P-TEFb), which is proposed to facilitate the transition from abortive to productive elongation by phosphorylating the CTD (carboxy-terminal domain) of the large subunit of RNA polymerase II (RNA Pol II).
Protein Families
Cyclin family, Cyclin C subfamily
Tissue Specificity
Ubiquitously expressed.
Buffer
Buffer: PBS with 0.02% sodium azide, 50% glycerol, pH7.3.
Format
liquid
Purification
Affinity purification
Purity
Affinity purification
Storage
Upon receipt, store at -20°C or -80°C. Avoid repeated freeze.
Storage Buffer
Store at -20oC or -80oC. Avoid freeze / thaw cycles. Buffer: PBS with 0.02% sodium azide, 50% glycerol, pH7.3.