Handout 11 - MCB252Cells&TissuesFall2008Handout11

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Handout 11 New questions: How is the expression of a gene regulated at the transcriptional  level? How is the expression of a gene regulated at the post- transcriptional level? How are mRNAs exported to the cytoplasm? What regulates protein homeostasis? III.b. Protein Mediated Translational Control
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Handout 11 III.b. Protein Mediated Translational Control
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Handout 11 III.b. Protein Mediated Translational Control MPMV = M ason-P fizer M onkey V irus (RNA virus) Unlike HIV, MPMV does not code for Rev, or a Rev equivalent. Accordingly, there is no RRE in the MPMV sequence. In contrast, the MPMV viral RNA contains a C onstitutive  T ransport E lement (CTE) that is responsible for its nuclear export. 5’ 3’ CTE Surprisingly, MPMV does not code for a CTE binding protein!
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Handout 11 III.b. Protein Mediated Translational Control This observation lead scientists to hypothesize that MPMV  depended solely on cellular factors for its function. 5’ 3’ CTE The activity of the CTE was found to depend on a cellular protein named NXF1/Tap (60 KDa) and its associated protein NXT1/P15. (Tap = T ip A ssociated P rotein) (Tip = T yrosine kinase I nteracting P rotein)
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Handout 11 III.b. Protein Mediated Translational Control CTEs are not found in cellular mRNAs. Surprisingly, cellular mRNA export relies on Tap and its associated protein P15! Tap and P15 are the major components of the so called “mRNA  transporter”. Both Tap and P15 were shown to form a heterodimer that directly  interacts with nucleoporins. Other factors were subsequently found to be implicated in mRNA  export. .......
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Handout 11 III.b. Protein Mediated Translational Control
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Handout 11 III.b. Protein Mediated Translational Control In addition, the polyA, the nuclear cap binding complex, the splicing machinery and the exon junction complexes are  implicated in the nuclear export of mRNPs. A A A A A A E xon J unction C omplex (EJCs) (deposited during splicing) N uclear C ap B inding  Complex (nCBP) PABPII 5’ 3’
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Handout 11 III.b. Protein Mediated Translational Control
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Handout 11 Involvement of SR proteins in mRNA export
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Handout 11 mRNP remodeling
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Handout 11 mRNP remodeling
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Handout 11 III.b. Protein Mediated Translational Control
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Handout 11 Mehlin et al., 1992 Cell 69: 605-613 Export of mRNPs through NPC Nucleus Cytoplasm
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This note was uploaded on 06/12/2010 for the course MCB 252 taught by Professor Prasanth during the Spring '08 term at University of Illinois at Urbana–Champaign.

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Handout 11 - MCB252Cells&TissuesFall2008Handout11

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