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.
Zhou
Meisheng
M
Department of Biochemistry and Molecular Biology, George Washington University School of Medicine, Washington, DC 20037, USA.
Deng
Longwen
L
Kashanchi
Fatah
F
Brady
John N
JN
Shatkin
Aaron J
AJ
Kumar
Ajit
A
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