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Title: Identification and characterization of tRNA-like sequence elements encoded by murine gammaherpesvirus 68
Author: Bowden, R.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1998
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Murine gammaherpesvirus 68 (MHV-68) is a virus of wild rodents which provides a laboratory model for many aspects of gammaherpesvirus infection. Gammaherpesviruses have a colinear arrangement of conserved genes interspersed with unique sequences, many of which have roles in latency or pathogenesis. The aim of this project has been to characterise a locus of MHV-68 which is positionally analogous to divergent loci of other gammaherpesviruses, in order to determine whether MHV-68 encodes either analogous or dissimilar genes. 6.2kb of MHV-68 unique DNA sequence at the left end of the genome was determined. 8 sequences were identified with primary and secondary structural characteristics of transfer RNAs (tRNAs), the first report of such sequences encoded by a virus of eukaryotes. Northern analysis of lytic viral infection indicated the abundant expression of small RNAs from a DNA segment encoding only tRNA-like sequences (vtRNAs). To confirm that such lytic cycle transcripts corresponded to vtRNAs, S1 analysis was performed, demonstrating that vtRNAs 5 and 6 were transcribed into mature tRNA-like molecules. Further, vtRNAs 4 and 6 were shown to be post-transcriptionally CCA-modified in a similar way to cellular tRNAs. Investigation of vtRNA function by acidic northern analysis showed that during lytic infection in cell culture, vtRNAs 3,4,5 and 6 were not significantly aminoacylated, indicating that the vtRNAs do not function conventionally in protein synthesis. In addition, two open reading frames and a partial coding sequence were identified which had no close relatives amongst published sequences: ORF1 has low level sequence similarity to both poxvirus serpins and the complete sequence of the truncated ORF3 derived from the recently published MHV-68 genomic sequence, however ORF3 is not significantly homologous to serpin sequences. Alignments indicated that the serpin active site was not conserved in ORF1 or ORF3, suggesting functional divergence. ORF2 has no detectable homologues amongst published sequences.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available