RNA VIRUS REPLICATION STRATEGIES

2. RNA VIRUS REPLICATION STRATEGIES

3. Objectives • Classes of RNA genomes Baltimore Classification • Different strategies used by RNA viruses • RNA replication and mRNA synthesis • Initiation, elongation and termination of replication • Examples

7. RNA -> RNA RNA-dependent RNA polymerase RNA -> DNA RNA-dependent DNA polymerase - reverse transcriptase Host cell DNA -> RNA DNA-dependent RNA polymerase RNA VIRUS STRATEGIES

8. ALL ANIMAL RNA VIRUSES CODE FOR A POLYMERASE

9. AAA Need to make mRNA PLUS (POSITIVE) SENSE RNA GENOMES proteins (+ve) sense mRNA

10. AAA Need to make mRNA MINUS (NEGATIVE) SENSE RNA GENOMES proteins (+ve) sense mRNA (-ve) sense genomic RNA

11. AAA Need to make mRNA MINUS (NEGATIVE) SENSE RNA GENOMES RNA polymerase must be packaged in virion. proteins (+ve) sense mRNA If used, RNA modifying enzymes are packaged in virion. (-ve) sense genomic RNA

12. AAA Need to make mRNA DOUBLE-STRANDED RNA GENOMES RNA polymerase must be packaged in virion. proteins (+ve) sense mRNA If used, RNA modifying enzymes are packaged in virion. Double-stranded genomic RNA

13. Need to make mRNA RETROVIRUSES Reverse transcriptase must be packaged in virion. DS DNA DS DNA +VE RNA

14. RNA viruses that do NOT have a DNA phase

15. RETROVIRUSES

17. GENOME SIZE • POLYMERASE • ATTACHMENT PROTEIN • CAPSID PROTEIN • RELATIVELY FEW OTHER PROTEINS • VIRION SIZE MAY BE QUITE LARGE BUT LIMITED NUMBER OF PROTEINS

18. mRNA AAAAAAAA RIBOSOMES PROTEIN AAAAAAAA The monocistronic mRNA problem • Make one monocistronic mRNA per protein • Make a primary transcript and use alternative splicing • Make a large protein and then cut it into smaller proteins • Include special features in the mRNA which enable ribosomes to bind internally

24. GENOME SIZE • TAUTOMERIZATION • PROOF READING