Nuclear Envelope Transport Quiz

Nuclear Transport

• Import of proteins into the nucleus is energy-dependent through the nuclear pore complexes.
• Nuclear localization signals (NLS) are rich in amino acids such as lysine, arginine, and proline.
• FG repeat sequences in the nuclear pore complex serve as the binding sites for import receptors.
• Importin protein-receptor complexes move along the nuclear pore complex by repeatedly binding, dissociating, and then re-binding to the adjacent FG repeat sequences.
• RanGEF (Ran Guanine nucleotide Exchange Factor) is responsible for promoting the exchange of GDP for GTP and converting Ran GDP to Ran GTP.

Export of RNAs

• The export of most tRNAs, rRNAs, and small nuclear RNAs out of the nucleus is mediated by the export receptor chromosomal region maintenance 1 (CRM1).
• The energy source for the export of all RNAs from the nucleus to the cytoplasm is RanGTP.
• The presence of a nuclear export signal (NES) determines whether an RNA will leave the nucleus.
• Inhibitory protein exportin-t inhibits the recognition of nuclear localization signal (NLS) by importin.
• RanGTPase-activating protein (RanGAP) promotes the conversion of Ran GTP to Ran GDP.

Export of mRNAs

• Nuclear export signals (NES) play a role in the export of RNAs from the nucleus.
• Inhibitory protein is degraded in stimulated cells, allowing specific proteins to enter the nucleus.
• The export receptor TAP (Tip-associated protein) is responsible for transporting mature mRNAs across nuclear pores as RNA-protein complexes.

Energy Source

• The primary energy source for the directional transport through nuclear pore complexes is RanGTP.