Organization of the NPC

Specificity Models of the NPC

Brownian Gate Selective Phase ‘Oily Spaghetti

Week 2: RNA maturation transport, & localization

RNA export to the cytoplasm: model systems

RNA degradation

Links between RNA processing, transport, degradationRNA localization in the cytoplasm

RNA processing: brief overview

Evidence for checkpoints?mRNA transport

Specific process for Pol II transcripts

nuclear CBC binds to m7G-cap: role in splicing, transport, stability (exchanged in cytoplasm)

Function in transport, stability, translation

CPSF: cleavage and polyadenylation specificity factor

CStF: cleavage stimulatory factor

CF: cleavage factor

PAP: polyA polymerase

PAB: polyA binding protein

Function in transport, stability, translation

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Compartments inside the nucleus

1. Nucleolus

2. Perichromatin granule clusters

Carter et al., Science (1993) 259: 1330

Balbiani Rings (Chironomus tentans)

SUMMARY

I. Multiple steps of mRNA biosynthesis are tightly coupled

II. Mex67/TAP is one major mRNA export factorBinding 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.