1. RNA maturation, transport & localization RNA export to the cytoplasm: model systems RNA degradation RNA localization in the cytoplasm

2. Balbiani Rings (Chironomus tentans)

3. BR RNP maturation

4. BR RNP translocation

7. SUMMARY I.Multiple steps of mRNA biosynthesis are tightly coupled II.Mex67/TAP is one major mRNA export factor Binding to mRNA may already occur at the site of transcription III.Many questions remain - How are mRNA substrates released in the cytoplasm? - Are there multiple mRNA export pathways? - How is processing and transport coupled? etc.

8. RNA half-lives vary greatly

9. AUUUA element regulates half-life

10. A. B. Casein mRNA prolactin + - 30,000 mRNA/cell 300 mRNA/cell No change in transcription

11. mRNA DEGRADATION mRNA DECAY NMD ‘turnover’‘surveillance’

12. mRNA DECAY AAA m7Gppp poly A shorteningDeadenylase complex AAAAAAAAAAAAAAAA m7Gppp DecapitationDecapping enzyme (DCP1 complex) AAA 5’-3’ exonucleolytic cleavageXrn1 complex

13. From Neu-Yilik et al. (2001) EMBO 20:532-540

14. m7Gppp Stop in penultimate exon/ 5’ of splicing mark AAAAAAAAAAAAAAAA DecapitationDecapping enzyme (DCP1 complex) 5’-3’ exonucleolytic cleavageXrn1 complex Nonsense Mediated Decay AAAAAAAAAAAAAAAA

15. RNA localization mRNA can be localized to subcellular compartments by actin or tubulin-dependent processes Examples: Xenopus: Vg1 mRNA (TGF  ) to vegetal pole Drosophila: nanos, oskar mRNA (posterior) and bicoid (anterior) (requires mRNA binding protein staufen) (requires staufen and miranda) prospero (into ganglion of mother cells; neuroblast TF) Yeast: Ash1 mRNA to daughter cell

17. lamellipodia stainingperinuclear staining in myotubes

18. Bertrand et al., Mol Cell (98) 2:437-445

20. SUMMARY 2 I.mRNA decay - regulated and non-regulated turn-over - ordered pathway (deadenylation, decapping, exonucleolytic degradation) - NMD: recognition of premature stop codons II.Cytoplasmic mRNA localization - ZIP code in 3’ UTR - both actin and tubulin-mediated - yeast mating type switch as a model: Ash1 mRNA localization (via 3’ UTR, She2/3, Myo4 and actin cables)