. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "PARP1 negatively regulates HIV-1 transcription by directly competing with Tat-P-TEFb complex for binding to TAR RNA" . "During HIV-1 Tat mediated transactivation of the HIV-1 LTR promoter, Tat stimulates the phosphorylation of the C-terminal domain (CTD) of RNA polymerase II by P-TEFb, leading to transcription elongation" . "The N-terminus (amino acids 1-48, including activation domain) of HIV-1 Tat binds to P-TEFb through a direct interaction with the N-terminus (amino acids 1-290) of cyclin T1 during Tat-mediated transactivation of the HIV-1 LTR promoter" . "HIV-1 Tat recruits P-TEFb to the HIV-1 Transcription Activation Response (TAR) RNA during Tat-mediated transactivation of the HIV-1 LTR promoter" . "Tat-SF1 is a required cofactor for HIV-1 Tat activity that complexes with P-TEFb and Tat, and stimulates Tat-mediated activation of the HIV-1 LTR promoter" . "P-TEFb is required for HIV-1 Tat-mediated transcriptional activation" . "The up and downregulation of expression of CDK9 and cyclin T1 or sequestration of cyclin T1 in infected cells may regulate HIV-1 latency by up or downregulating HIV-1 Tat transcriptional activation" . "The interaction of HIV-1 Tat with HIV-1 Transcription Activation Response (TAR) RNA is enhanced by the interaction of Tat with P-TEFb, and TAR RNA also enhances the interaction between Tat and cyclin T1" . "Amino acids 260-263 of cyclin T1 are critical for HIV-1 Tat-mediated transcriptional activation, and mediate the species specificity of cyclin T1 and P-TEFb binding to Tat" . "P-TEFb interacts with HIV-1 Tat as part of both the HIV-1 transcription preinitiation and elongation complexes" . "Acetylation of HIV-1 Tat by cellular histone acetyltransferases regulates the binding of Tat to P-TEFb" . "Hsp70 and Hsp90/Cdc37 stabilize CDK9 as well as the assembly of an active P-TEFb complex which is stimulated by HIV-1 Tat during HIV-1 transcriptional activation" . "HIV-1 Tat competes with CIITA for the binding to P-TEFb, leading to the downregulation of MHC class II gene expression" . "The human I-mfa domain-containing protein (HIC) interacts with both P-TEFb and HIV-1 Tat, and modulates Tat transactivation of the HIV-1 LTR promoter" . "HIV-1 Tat stimulates the phosphorylation of SPT5 by P-TEFb during transactivation of the HIV-1 LTR promoter" . "P-TEFb regulates HIV-1 Tat-mediated activation of transcription through two built-in auto inhibitory mechanisms, autophosphorylation of CDK9 and cyclin T1 binding to the transcription elongation factor Tat-SF1" . "Cyclin T1 is capable of recruiting CDK9 and HIV-1 Tat to splicing factor-rich nuclear speckle regions, suggesting nuclear speckles are a site of P-TEFb and Tat function" . "The p160 nuclear receptor co-activator GRIP1 binds to the N-terminal region of HIV-1 Tat, bridging HIV-1 LTR promoter-bound factors to the Tat-P-TEFb complex and enhancing the transactivating activity of Tat" . "P-TEFb, Puralpha and HIV-1 Tat cooperate to activate the TNFalpha promoter" . "The growth factor granulin and the promyelocytic leukemia (PML) protein regulate HIV-1 Tat-mediated transcriptional activation by competing with the Tat interaction with cyclin T1/P-TEFb" . "MAQ1 and 7SK RNA interact with P-TEFb and compete with the binding of HIV-1 Tat to cyclin T1, suggesting the TAR RNA/Tat lentivirus system evolved to subvert the cellular 7SK RNA/MAQ1 system" . "HIV-1 Tat-mediated stimulation of RNA polymerase II C-terminal domain phosphorylation by P-TEFb leads to stimulation of co-transcriptional capping of HIV-1 mRNA" . "SKIP is required for Tat transactivation in vivo and stimulates HIV-1 transcription elongation by associating with CycT1:CDK9 (P-TEFb) and Tat:P-TEFb complexes both in nuclear extracts and in recombinant Tat:P-TEFb:TAR RNA complexes in vitro" . "HIV-1 Tat and P-TEFb undergo constant association and dissociation cycles with TAR and the elongating polymerase in living cells" . "A La-related protein, LARP7, is associated with P-TEFb, HEXIM1/2, MEPCE, and 7SK RNA in a large stable complex form. Knockdown of LARP7 decreases the steady-state level of 7SK, but increases free P-TEFb and enhances Tat-mediated transcription" . "Mutant CycT1 protein containing triple T-to-A mutations in the N-terminal region (amino acids T143, T149, and T155) associates with CDK9 and HIV-1 Tat as a kinase-negative complex and blocks HIV transactivation" . "Undetectable CycT1 protein and un-phosphorylation of CDK9 in undifferentiated monocytes result in the lack of Tat transactivation of the LTR promoter in early viral life cycle" . "HIV-1 Tat forms at least two distinct P-TEFb-containing complexes. Tatcom1 is composed of P-TEFb, AF9, ENL, ELL, AFF1, AFF4, and PAF1, presenting strong CTD-kinase activity, while Tatcom2 consists of 7SK, LARP7, and MEPCE with two molecules of Tat/P-TEFb" . "Interaction of P-TEFb with histone H1 results in its phosphorylation at position Ser-183 in a Tat-dependent manner, which is necessary for transcription from the HIV-1 LTR" . "TAR binds Tat and P-TEFb as it emerges on the nascent transcript, competitively displacing the inhibitory 7SK snRNP (HEXIM1 and LARP7) and activating the P-TEFb kinase" . "HIV-1 Tat-mediated release of P-TEFb from the 7SK sn RNP results in a conformational change in 7SK RNA and release of HEXIM1 from the complex" . "The P-TEFb binding region (amino acids 1209-1362) of BRD4 is required for HIV-1 Tat-mediated release of P-TEFb from the 7SK snRNP" . "HIV-1 Q35L mutant fails to efficiently bind either CDK9 or CycT1 resulting in the defective gene expression. However, the I39Q mutation rescues the Q35L mutant's loss of function" . "CDK11 depletion reduces protein expression of CDK9 and HEXIM1 and Tat transactivation of HIV-1 provirus" . "Overexpression of CDK9 or CDK9 mutants inhibits HIV-1 Tat transcriptional activation" . "TFIIH inhibits the phosphorylation of CDK9 in the HIV-1 transcription preinitiation complex, while HIV-1 Tat stimulates CDK9 autophosphorylation to activate transcription elongation" . "HIV-1 Tat-induced kinase activity of P-TEFb is highly sensitive to flavopiridol, a CDK inhibitor. P-TEFb-mediated phosphorylation of RNAP II CTD, SPT5, and Tat-SF1 during HIV-1 transcription elongation is also highly sensitive to flavopiridol" . "Cdk9, the catalytic subunit of P-TEFb, is ubiquitinated by Skp1/Cul1/F-box protein E3 ubiquitin ligase Skp2, which facilitates the formation of the RNA-protein complex between P-TEFb, Tat, and TAR, thereby enhancing Tat transactivation" . "Tat-C/EBPbeta association is mediated through cdk9, which phosphorylates C/EBPbeta. C/EBPbeta-cyclin T1 association requires the presence of cdk9" . "HIV-1 Tat competes with HEXIM1 for binding to 7SK RNA and inhibits the formation of the P-TEFb-HEXIM1-7SK complex. Tat binds to nucleotides 10-48 of 7SK RNA" . "HIV-1 infection leads to activation of P-TEFb due to HIV-1 Tat-mediated release of P-TEFb from the large form" . "CDK9 is involved in Tat-induced MCP-1/CCL2 gene expression in human astrocytes" . "HIV-1 Tat increases the amount of ELL2 bound to P-TEFb without affecting the AFF4-P-TEFb binding. CDK9 is required for the Tat-induced ELL2 accumulation and Tat interaction with ELL2" . "Inhibition of Ca(2+) signaling leads to dephosphorylation of Thr186 on CDK9, which results in the decreased transactivation of the HIV-1 LTR by HIV-1 Tat" . "ATP analogs are effective inhibitors of HIV-1 Tat-mediated activated transcription with a decreased loading of CDK9 onto the HIV-1 DNA" . "interacts with" . "inhibited by" . "cooperates with" . "regulated by" . "requires" . "binds" . "associates with" . "stimulates" . "activates" . "recruits" . "induces release of" . "complexes with" . "enhanced by" . "recruited by" . "phosphorylates" .