title: Multiple roles for ATP in the synthesis and processing of mRNA by vaccinia virus: specific inhibitory effects of adenosine (beta,gamma-imido) triphosphate.
abstract: Adenosine (beta,gamma-imido)triphosphate (AMP-PNP) and guanosine (beta,gamma-imido)triphosphate (GMP-PNP) are analogs of ATP and GTP with non-hydrolyzable gamma-phosphates. Although both AMP-PNP and GMP-PNP were used in place of ATP and GTP by Escherichia coli RNA polymerase to transcribe vaccinia virus DNA, only GMP-PNP was used by the transcriptase present within vaccinia virus cores. AMP-PNP specifically prevented initiation of transcription, since RNA initiated in the presence of ATP, GTP, and CTP was subsequently elongated by incubating the washed cores in the presence of AMP-PNP, GTP, CTP, and UTP. The RNA formed in this manner, however, was (i) several times longer than normal transcripts, indicating a defect in chain termination and/or cleavage of nascent RNA, (ii) was not polyadenylylated (although free polyadenylic acid formed), and (iii) was not extruded from the virus cores. Nearest neighbor analysis demonstrated that AMP-PNP was incorporated adjacent to all four nucleotides, and hybridization to restriction endonuclease fragments of vaccinia virus DNA indicated that the high-molecular-weight RNA was transcribed from representative fractions of the entire genome. The possibility of a block in processing rather than or in addition to a block in chain termination was suggested by the cleavage of the high-molecular-weight RNA within the core after replacement of AMP-PNP with ATP. Cleavage of purified high-molecular-weight RNA by a soluble endoribonuclease extracted from vaccinia virus cores, however, was not dependent upon ATP, nor was it inhibited by AMP-PNP. The latter results suggest that AMP-PNP blocks a step preceding cleavage.
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D008970:Molecular Weight; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000096:biosynthesis*; D012367:RNA, Viral / Q000096:biosynthesis* / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism; D014616:Vaccinia virus / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D012367:RNA, Viral; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D012260:Ribonucleases