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Unformatted text preview: J OURNAL OF VIROLOGY, Dec. 2002, p. 13062–13068 Vol. 76, No. 24 0022-538X/02/$04.00 1 0 DOI: 10.1128/JVI.76.24.13062–13068.2002 Copyright © 2002, American Society for Microbiology. All Rights Reserved. Mutations Affecting Transcriptional Termination in the P Gene End of Subacute Sclerosing Panencephalitis Viruses Minoru Ayata, 1 * Katsuhiro Komase, 2 Masashi Shingai, 1 Isamu Matsunaga, 1 Yuko Katayama, 1 and Hisashi Ogura 1 Department of Virology, Osaka City University Medical School, Osaka 545-8585, 1 and Division of Research and Development, Center for Biologicals, The Kitasato Institute, Tokyo 108-8642, 2 Japan Received 11 March 2002/Accepted 4 September 2002 Numerous mutations are found in subacute sclerosing panencephalitis (SSPE) viruses, and the M gene is the gene most commonly affected. In some SSPE viruses, such as the MF, Osaka-1, Osaka-2, and Yamagata-1 strains, translation of the M protein is complicated by a transcriptional defect that leads to an almost exclusive synthesis of dicistronic P-M mRNA. To understand the molecular mechanisms of this defect, we sequenced the P gene at the P-M gene junction for several virus strains and probed the involvement of several mutations in the readthrough region via their expression in measles virus minigenomes containing different sequences of the P-M gene junction and flanking reporter genes. The deletion of a single U residue in the U tract of the Osaka-1 strain (3 *-UAAUAUUUUU-5 * ) compared with the consensus sequence resulted in a marked reduction of the expression of the downstream reporter gene. In addition, the expression of the downstream gene was markedly decreased by (i) the substitution of a C residue in the U tract of the P gene end of the OSA-2/Fr/B strain of the Osaka-2 virus (3 *-UGAUAUUCUU-5 * compared with the sequence 3 *-UGAUAUUUUU-5 * from a sibling virus of the same strain, OSA-2/Fr/V), and (ii) the substitution of a G in the sequence of the P gene end of the Yamagata-1 strain at a variable site immediately upstream from the six-U tract (3 *-UGAUGUUUUUU-5 * instead of 3 *-UGAUUUUUUUU-5 * ). Mutations at the P gene end can account for the readthrough transcrip- tion variation at the P-M gene junction, which directly affects M protein expression. Measles virus (MV) is a member of Paramyxoviridae , and its genome is a nonsegmented single-stranded RNA of negative polarity. The MV genome contains N, P/C/V, M, F, H, and L genes, with the L gene encoding an RNA-dependent RNA polymerase (8). The viral RNA polymerase synthesizes the antigenome, which serves as a template for a precise copy of the genomic RNA. Also, each gene is transcribed sequentially from the 3 9 end of the genome by the same RNA polymerase (24). One of the characteristics of the MV genome is that the conserved transcriptional control regions are at the gene boundaries. Each gene is separated by an intergenic region of three nucleotides that is not copied into mRNA (17). Usually, most mRNAs are monocistronic RNA because the transcrip-...
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