Transcription elongation factor P-TEFb is required for HIV-1 tat transactivation in vitro.
P-TEFb is a key regulator of the process controlling the processivity of RNA polymerase II and possesses a kinase activity that can phosphorylate the carboxy-terminal domain of the largest subunit of RNA polymerase II. Here we report the cloning of the small subunit of Drosophila P-TEFb and the finding that it encodes a Cdc2-related protein kinase. Sequence comparison suggests that a protein with 72% identity, PITALRE, could be the human homolog of the Drosophila protein. Functional homology was suggested by transcriptional analysis of an RNA polymerase II promoter with HeLa nuclear extract depleted of PITALRE. Because the depleted extract lost the ability to produce long DRB-sensitive transcripts and this loss was reversed by the addition of purified Drosophila P-TEFb, we propose that PITALRE is a component of human P-TEFb. In addition, we found that PITALRE associated with the activation domain of HIV-1 Tat, indicating that P-TEFb is a Tat-associated kinase (TAK). An in vitro transcription assay demonstrates that the effect of Tat on transcription elongation requires P-TEFb and suggests that the enhancement of transcriptional processivity by Tat is attributable to enhanced function of P-TEFb on the HIV-1 LTR.
Zhu
Y
Y
Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242 USA.
Pe'ery
T
T
Peng
J
J
Ramanathan
Y
Y
Marshall
N
N
Marshall
T
T
Amendt
B
B
Mathews
M B
MB
Price
D H
DH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D042863:Cyclin-Dependent Kinase 9; D017931:DNA Primers; D004330:Drosophila / Q000201:enzymology / Q000235:genetics; D015696:Gene Products, tat / Q000096:biosynthesis / Q000378:metabolism*; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D042925:Positive Transcriptional Elongation Factor B; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000737:chemistry; D012319:RNA Polymerase II / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry; D016415:Sequence Alignment; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D054322:tat Gene Products, Human Immunodeficiency Virus
D017931:DNA Primers; D015696:Gene Products, tat; D011993:Recombinant Fusion Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D011494:Protein Kinases; C060137:carboxy-terminal domain kinase; D042925:Positive Transcriptional Elongation Factor B; D017346:Protein Serine-Threonine Kinases; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9; D012319:RNA Polymerase II