1. From Gene to RNA Kanokporn Boonsirichai Molecular Biology of the Cell. 2002. Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter.

2. Figure 7-10 Essential Cell Biology (© Garland Science 2010) Orientation matters in transcription

3. Question to consider  Could RNA polymerase used for transcription be used as the polymerase (primase) that makes RNA primer required for replication? Why or why not?

4. RNA Processing Kanokporn Boonsirichai Molecular Biology of the Cell. 2002. Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter.

5. Figure 7-17 Essential Cell Biology (© Garland Science 2010) Gene organization  Bacteria  Uninterrupted coding sequence  Genes are grouped together in an “operon”.  Eukaryotes  Coding sequence is interrupted by “introns”.  Coding sequence is broken into pieces of “exons”. gene A gene Bgene C promoter

6. mRNA Processing Pre-mRNA Mature mRNA

7. Eukaryotic mRNA Processing  Capping  Addition of 7-methylguanosine at the 5’ end  Splicing  Removal of introns  3’cleavage  Cleavage of the transcript at the 3’end of the gene  Polyadenylation  Addition of 150-250 adenine ribonucleotides at the 3’ end

8. 1. Addition of 5’ cap

10. 2. Pre-mRNA Splicing: removal of introns  Splicing signals are located in the transcript itself. R = purine (A or G) Y = pyrimidine (C or T) N = any one of the 4 bases

11.  2’-OH is utilized to form a lariat structure Branch point

12. Spliceosome  A complex of snRNPs (small ribonucleoproteins)

13. Interactions among snRNPs are mediated by their snRNAs

14. How is Fidelity Achieved?  snRNAs are associated with snRNPs.  Several components of the spliceosome are carried on the phosphorylated tail of RNA polymerase(to keep track of introns and exons).  The “exon definition hypothesis”  Exon size is somewhat uniform (averaging about 150 nucleotide pairs).  Exon-intron boundaries are marked with spliceosome components

16. Other Splicing Systems Transplicing => attachment of two different RNAs

17. What might be the importance of RNA splicing?

18. Alternative splicing allows for the production of multiple related proteins from a single transcript.

19. Processing of the 3’ end  Cleavage factors  Poly-A polymerase

20.  Cleavage signals  Poly-A addition

21. Mature mRNAs are exported from the nucleus

22. Questions to consider  What do you think might be the reasons for the eukaryotes to have their mRNA processed?