title: mRNA guanylation catalyzed by the S-adenosylmethionine-dependent guanylyltransferase of bamboo mosaic virus.
abstract: The S-adenosylmethionine-dependent guanylyltransferase of bamboo mosaic virus belongs to a novel class of mRNA capping enzymes distantly conserved in Alphavirus-like superfamily. The reaction sequence of the viral enzyme has been proposed comprising steps of 1) binding of GTP and S-adenosylmethionine, 2) formation of m7GTP and S-adenosylhomocysteine, 3) formation of the covalent (Enzyme-m7GMP) intermediate, and 4) transfer of m7GMP from the intermediate to the RNA acceptor. In this study the acceptor specificity of the viral enzyme was characterized. The results show that adenylate or guanylate with 5'-diphosphate group is an essential feature for acceptors, which can be RNA or mononucleotide, to receive m7GMP. The transfer rate of m7GMP to guanylate is greater than to adenylate by a factor of approximately 3, and the K(m) value for mononucleotide acceptor is approximately 10(3)-fold higher than that for RNA. The capping efficiency of the viral genomic RNA transcript depends on the length of the transcript and the formation of a putative stem-loop structure, suggesting that mRNA capping process may participate in regulating the viral gene expression.
authors.affiliation: Graduate Institute of Biotechnology, National Chung Hsing University, 250 Kuo-Kuang Rd., Taichung, Taiwan 40227, Republic of China.
authors.forename: Yih-Leh
authors.initials: YL
authors.lastname: Huang
authors.forename: Yau-Heiu
authors.initials: YH
authors.lastname: Hsu
authors.forename: Yu-Tsung
authors.initials: YT
authors.lastname: Han
authors.forename: Menghsiao
authors.initials: M
authors.lastname: Meng
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry; D001483:Base Sequence; D002384:Catalysis; D002855:Chromatography, Thin Layer; D003432:Cross-Linking Reagents / Q000494:pharmacology; D011756:Diphosphates / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000737:chemistry; D015870:Gene Expression; D006153:Guanosine Diphosphate / Q000737:chemistry; D006157:Guanosine Monophosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry; D008969:Molecular Sequence Data; D009029:Mosaic Viruses / Q000201:enzymology*; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000737:chemistry* / Q000378:metabolism; D013997:Time Factors
chemical_list: D003432:Cross-Linking Reagents; D011756:Diphosphates; D012333:RNA, Messenger; D006153:Guanosine Diphosphate; D000244:Adenosine Diphosphate; D012313:RNA; D012436:S-Adenosylmethionine; D006157:Guanosine Monophosphate; D006160:Guanosine Triphosphate; D004492:Edetic Acid; D008274:Magnesium