1. RNA processing

2. RNA species in cells

3. RNA processing

4. Types of introns and their removal

5. Types of introns

6. Complex organisms have intron-rich genes

7. Examples of introns in human protein-coding genes

8. Removal of introns from mRNA in the nucleus of eukaryotes

9. Consensus elements of human GU-AG introns

10. Chemistry of mRNA splicing for GU-AG introns

11. Three way junction at the internal (A) branch site

12. U1 snRNP

13. Spliceosome-catalyzed splicing of GU-AG introns

14. Different snRNPs and proteins bind and dissociate during splicing

15. Similarities in spliceosome-catalyzed removal of introns and self-splicing group I and group II introns

16. Possible errors in splice-site selection

17. SR proteins are essential for correct splice-site selection ESE = exonic splicing enhancers SR proteins = serine, arginine-rich proteins

18. Trans-splicing joins exons from different RNAs

19. Splicing of AU-AC introns by “minor” spliceosomes proceeds as for GU-AG introns

20. Alternative splicing results in alternative mRNAs that are translated into different proteins

22. Figure 12.34 Genomes 3 (© Garland Science 2007) Alternative splicing of the human slo gene (codes for a membrane protein that regulates the flow of potassium ions across the membrane) Optional exons participating in alternative splicing events. About 500 mRNA variants are produced in cells of the inner ear.

23. Alternative splicing is regulated

24. Assembly of major and minor spliceosomes Nonsense-mediated transcript decay

25. Example: alternative splicing in Drosophila Dscam transcripts

26. Example: mutual exclusive alternative splicing of exon 6 in Drosophila Dscam transcripts

27. Splicing activators and repressors

29. Exons may code for protein domains

30. Exon shuffling may lead to protein diversity

31. Exon shuffling may be responsible for protein diversity

32. Figure 12.40 Genomes 3 (© Garland Science 2007) Removal of introns from tRNAs

33. RNA processing

34. Processing of ribosomal RNA by cutting and trimming

35. Figure 12.17 Genomes 3 (© Garland Science 2007) Processing of a tRNA by cutting and trimming

36. RNA processing

37. Figure 12.18 Genomes 3 (© Garland Science 2007) Chemical modifications in tRNAs

38. Figure 12.41a Genomes 3 (© Garland Science 2007) Methylation of ribosomal RNAs

39. RNA editing in apolipoprotein B mRNA

40. Deamination of bases leads to codon changes

41. RNA-guided insertion of Us into mRNAs

42. Processing of RNAs is required for transport into the cytoplasm