140 likes | 257 Views
The Human Tap Nuclear RNA Factor Contains a Novel Transportin-dependent Nuclear Localization Signal That Lacks Nuclear Export Signal Function Ray Truant, Yibin Kang, and Bryan R. Cullen. 871602 Shishi’s seminar 2000,11,16. Background:
E N D
The Human Tap Nuclear RNA Factor Contains a Novel Transportin-dependent Nuclear Localization Signal That Lacks Nuclear Export Signal FunctionRay Truant, Yibin Kang, and Bryan R. Cullen 871602 Shishi’s seminar 2000,11,16
Background: ‧ At least two possible protein mediators of mRNA export exist: heterogeneous nuclear ribonucleoproteins (hnRNPs) and Tap protein. ‧ Definitions of importinαβ , importin β binding domain (IBB) , nuclear localization signal (NLS) , nuclear export signal (NES) , transportin (Trn) , hnRNP A1 and M9 . ‧ M9: NLS/NES Tap-N: NLS
Background: ‧ At least two possible protein mediators of mRNA export exist: heterogeneous nuclear ribonucleoproteins (hnRNPs) and Tap protein. ‧ Definitions of importinαβ , importin β binding domain (IBB) , nuclear localization signal (NLS) , nuclear export signal (NES) , transportin (Trn) , hnRNP A1 and M9 . ‧ M9: NLS/NES Tap-N: NLS
‧ Functional domain organization of human Tap
Transportin is necessary and sufficient for Tap-N-NLS-dependent nuclear import. ‧Competitive nuclear import assays.
‧ Transportin is sufficient for Tap-N-NLS-dependent nuclear import.
Direct binding of the Tap-N-NLS by Trn ‧In vitro binding assays.
Functional comparison of M9 and Tap-N-NLS ‧ Heterokaryon fusion nuclear shuttling assay.
Three types of Trn-dependent protein NLS sequences. ‧M9: specific for Trn , NLS/NES . ‧Ribosomal proteins: can also be mediate by Impβ ,NLS , no homology to M9. ‧Tap: no homology to M9 , but specific for Trn , compete with M9 , but lacks NES . Trn nuclear import factor may have evolved a specialized role to the return of mRNA export factors to the nucleus.