CRM1 and Ran are present but a NES-CRM1-RanGTP complex is not required in Balbiani ring mRNP particles from the gene to the cytoplasm

• Messenger RNA is formed from precursors known as pre-mRNA. Theseprecursors associate with proteins to form pre-mRNA-protein(pre-mRNP) complexes. Processing machines cap, splice and polyadenylatethe pre-mRNP and in this way build the mRNP. These processingmachines also affect the export of the mRNP complexes from thenucleus to the cytoplasm. Export to the cytoplasm takes placethrough a structure in the nuclear membrane called the nuclearpore complex (NPC). Export involves adapter proteins in themRNP and receptor proteins that bind to the adapter proteinsand to components of the NPC. We show that the export receptorchromosomal region maintenance protein 1 (CRM1), belonging toa family of proteins known as importin-ß-like proteins,binds to gene-specific Balbiani ring (BR) pre-mRNP while transcriptiontakes place. We also show that the GTPase known as Ran bindsto BR pre-mRNP, and that it binds mainly in the interchromatin.However, we also show using leptomycin B treatment that a NES-CRM1-RanGTPcomplex is not essential for export, even though both CRM1 andRan accompany the BR mRNP through the NPC. Our results thereforesuggest that several export receptors associate with BR mRNPand that these receptors have redundant functions in the nuclearexport of BR mRNP.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

Gene expression

mRNA export

Export receptors

Molecular biology

Molekylärbiologi

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