The Tat/TAR-dependent phosphorylation of RNA polymerase II C-terminal domain stimulates cotranscriptional capping of HIV-1 mRNA.
The HIV type 1 (HIV-1) Tat protein stimulates transcription elongation by recruiting P-TEFb (CDK9/cyclin T1) to the transactivation response (TAR) RNA structure. Tat-induced CDK9 kinase has been shown to phosphorylate Ser-5 of RNA polymerase II (RNAP II) C-terminal domain (CTD). Results presented here demonstrate that Tat-induced Ser-5 phosphorylation of CTD by P-TEFb stimulates the guanylyltransferase activity of human capping enzyme and RNA cap formation. Sequential phosphorylation of CTD by Tat-induced P-TEFb enhances the stimulation of human capping enzyme guanylyltransferase activity and RNA cap formation by transcription factor IIH-mediated CTD phosphorylation. Using an immobilized template assay that permits isolation of transcription complexes, we show that Tat/TAR-dependent phosphorylation of RNAP II CTD stimulates cotranscriptional capping of HIV-1 mRNA. Upon transcriptional induction of latently infected cells, accumulation of capped transcripts occurs along with Ser-5-phosphorylated RNAP II in the promoter proximal region of the HIV-1 genome. Therefore, these observations suggest that Tat/TAR-dependent phosphorylation of RNAP II CTD is crucial not only in promoting transcription elongation but also in stimulating nascent viral RNA capping.
Department of Biochemistry and Molecular Biology, George Washington University School of Medicine, Washington, DC 20037, USA.
Meisheng
M
Zhou
Longwen
L
Deng
Fatah
F
Kashanchi
John N
JN
Brady
Aaron J
AJ
Shatkin
Ajit
A
Kumar
D001665:Binding Sites; D015696:Gene Products, tat / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D010766:Phosphorylation; D012315:RNA Caps / Q000235:genetics*; D012319:RNA Polymerase II / Q000737:chemistry* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics*; D012367:RNA, Viral / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012265:Ribonucleotides / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism; D014158:Transcription, Genetic; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D012315:RNA Caps; D012333:RNA, Messenger; D012367:RNA, Viral; D011993:Recombinant Fusion Proteins; D012265:Ribonucleotides; D014157:Transcription Factors; D054322:tat Gene Products, Human Immunodeficiency Virus; D012319:RNA Polymerase II