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Transport through the nuclear pores

Transport through the nuclear pores The NLS and NES consist of short sequences that are necessary and sufficient for proteins to be transported through the nuclear pores. Transport receptors have the dual properties of recognizing NLS or NES sequences and binding to the nuclear pore.

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Transport through the nuclear pores

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  1. Transport through the nuclear pores • The NLS and NES consist of short sequences that are necessary and sufficient for proteins to be transported through the nuclear pores. • Transport receptors have the dual properties of recognizing NLS or NES sequences and binding to the nuclear pore. • The direction of transport is controlled by the state of the monomeric G protein, Ran. • The nucleus contains Ran-GTP, which stabilizes export complexes, while the cytosol contains Ran-GDP, which stabilizes import complexes. • The mechanism of movement does not involve a motor.

  2. Summary of methods to assess mRNA stability in eukaryotic cells

  3. mRNA degradative activities in mammalian cells • Decapping • DCP2 which binds RNA as a prerequisite for cap recognition. • DCP1 augments DCP2 activity • LSM (SM-LIKE) PROTEINS augment DCP2 activity • 5’ -to-3’ exonuclease activity • XRN1 is a proven 5’ -to-3’ exonuclease that localizes to the cytoplasm. • RAT1/XRN2 is only thought to be a 5’ -to-3’ exonuclease on the basis of its similarity to the yeast orthologue. • Deadenylation • PARN is one of five mammalian homologues to yeast Caf1/Pop2 protein • 3’ -to-5’ exonuclease activity • Exosome (six RNase-PH-DOMAIN components, PM/SCL75,MTR3,RRP41, RRP42, RRP43 and RRP46; three S1 and KH RNA-binding components,RRP4, RRP40 and CSL4; the RNASE D-like components PM/SCL100; the putative helicaseKIAA0053; and a protein that is phosphorylated in the M phase of the cell) • PMR1-like activity • Polysomal ribonuclease 1 (PMR1) is a polysome-associated mRNA endonuclease

  4. ARE-binding proteins • AUBF, AU binding factor ; AU-A, AU binding factor-A ; AU-B, AU binding factor-B ; AU-C, AU binding factor-C ; hnRNP, heterogeneous nuclear ribonucleoprotein ; KH, hnRNP-K homology domain; KSRP, KH-type splicing regulatory protein 1; ND, not determined; PBMC, peripheral blood mononuclear cell.

  5. AUG UAG mGppp AAAAAAAAAAAAAAAA 3 3 3 3 RF 3 3 mGppp AAAAAAAAAAAAAAAA UAG 1 2 2 2 2 mGpp p AAAAAAAAAAAAAAAA UAG Meccanismo dell’ NMD

  6. RNA interference • Meccanismo • Significato biologico • Strumento di analisi della funzione dei geni

  7. Co-soppressione Introduzione di copie transgeniche di un gene risulta nella ridotta espressione del transgene e del gene endogeno RNA interference Introduzione di RNA a doppio filamento (dsRNA) induce silenziamento genico

  8. Componenti dell’RNAi • siRNA (small interfering RNA) = frammenti di RNA 21-25 nt • Dicer = endoribonucleasi specifica per dsRNA (tipo RNasi III) • RISC (RNA-induced silencing complex) = complesso ribonucleoproteico • RdRP (RNA-dependent RNA polymerase)

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