Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The influenza RNA-dependent RNA polymerase (RdRp) both replicates the flu's RNA genome and transcribes its mRNA. Replication occurs de novo; however, initiation of transcription requires a 7-methylguanosine 5'-capped primer that is "snatched" from host mRNA via endonuclease and cap binding functions of the influenza polymerase. A key question is how the virus regulates the relative amounts of transcription and replication. We found that the concentration of a capped cellular mRNA, the concentration of the 5' end of the viral RNA, and the concentration of RdRp all regulate the relative amounts of replication versus transcription. The host mRNA, from which the RdRp snatches its capped primer, acts to upregulate transcription and repress replication. Elevated concentrations of the RdRp itself switch the influenza polymerase toward replication, likely through an oligomerization of the polymerase. The 5' end of the vRNA template both activates replication and inhibits transcription of the vRNA template, thereby indicating that RdRp contains an allosteric binding site for the 5' end of the vRNA template. These data provide insights into the regulation of RdRp throughout the viral life cycle and how it synthesizes the appropriate amounts of viral mRNA and replication products (vRNA and cRNA).
 ...
PMID:Regulation of influenza RNA polymerase activity and the switch between replication and transcription by the concentrations of the vRNA 5' end, the cap source, and the polymerase. 2103 26

The PA, PB1, and PB2 subunits, components of the RNA-dependent RNA polymerase of influenza A virus, are essential for viral transcription and replication. The PB2 subunit binds to the host RNA cap (7-methylguanosine triphosphate (m(7)GTP)) and supports the endonuclease activity of PA to "snatch" the cap from host pre-mRNAs. However, the structure of PB2 is not fully understood, and the functional sites remain unknown. In this study, we describe a novel Val/Arg/Gly (VRG) site in the PB2 cap-binding domain, which is involved in interaction with acetyl-CoA found in eukaryotic histone acetyltransferases (HATs). In vitro experiments revealed that the recombinant PB2 cap-binding domain that includes the VRG site interacts with acetyl-CoA; moreover, it was found that this interaction could be blocked by CoA and various HAT inhibitors. Interestingly, m(7)GTP also inhibited this interaction, suggesting that the same active pocket is capable of interacting with acetyl-CoA and m(7)GTP. To elucidate the importance of the VRG site on PB2 function and viral replication, we constructed a PB2 recombinant protein and recombinant viruses including several patterns of amino acid mutations in the VRG site. Substitutions of the valine and arginine residues or of all 3 residues of the VRG site to alanine significantly reduced the binding ability of PB2 to acetyl-CoA and its RNA polymerase activity. Recombinant viruses containing the same mutations could not be replicated in cultured cells. These results indicate that the PB2 VRG sequence is a functional site that is essential for acetyl-CoA interaction, RNA polymerase activity, and viral replication.
...
PMID:A novel functional site in the PB2 subunit of influenza A virus essential for acetyl-CoA interaction, RNA polymerase activity, and viral replication. 2506 5

The PA, PB1, and PB2 subunits, components of the RNA-dependent RNA polymerase of influenza A virus, and the nucleoprotein (NP) interact with the genomic RNA of influenza viruses and form ribonucleoproteins. Especially, the PB2 subunit binds to the host RNA cap [7-methylguanosine triphosphate (m7GTP)] and supports the endonuclease activity of PA to "snatch" the cap from host pre-mRNAs. In this study, we describe a novel Val/Arg/Gly (VRG) site in the PB2 cap-binding domain, which is necessary for interaction with acetyl-CoA found in eukaryotic histone acetyltransferases (HATs). In vitro experiments revealed that the recombinant PB2 cap-binding domain that includes the VRG site interacts with acetyl-CoA; moreover, it was found that this interaction could be blocked by CoA and various HAT inhibitors. Interestingly, m7GTP also inhibited this interaction, suggesting that the same active pocket is capable of interacting with acetyl-CoA and m7GTP. To elucidate the importance of the VRG site on PB2 function and viral replication, we constructed a PB2 recombinant protein and recombinant viruses including several patterns of amino acid mutations in the VRG site. Substitutions of 2 or 3 amino acid residues of the VRG site to alanine significantly reduced PB2's binding ability to acetyl-CoA and its RNA polymerase activity. Recombinant viruses containing the same mutations could not be replicated in cultured cells. These results indicate that the PB2 VRG sequence is a functional site that is essential for acetyl-CoA interaction, RNA polymerase activity, and viral replication. I will also discuss some novel functions of NP in this review.
 ...
PMID:Structural and Biochemical Analyses on the RNA-dependent RNA Polymerase of Influenza Virus for Development of Novel Anti-influenza Agents. 2815 33