Trypanosomes can initiate nuclear export co-transcriptionally

ABSTRACT: The nuclear envelope serves as important mRNA surveillance system. In yeast and human, several control systems act in parallel to prevent nuclear export of unprocessed mRNAs. Trypanosomes lack homologues to most of the involved proteins and their nuclear mRNA metabolism is non-conventional exemplified by polycistronic transcription and mRNA processing by trans-splicing. We here visualised nuclear export in trypanosomes by probing large, endogenous mRNA by intramolecular multi-colour single molecule FISH (smFISH). In addition, unspliced mRNAs were visualised by co-probing two adjacent introns or intergenic regions. We found that the initation of nuclear export requires neither the completion of transcription nor trans-splicing. Nevertheless, the inhibition of trans-splicing blocked cytoplasmic transport of the of unspliced mRNAs and only a small fraction reached the nucleus-distant cytoplasm. Most of the unspliced transcripts remained at the nuclear periphery, within transport and in nuclear periphery granules (NPGs) localised at the cytoplasmic site of nuclear pores that resemble stress granules in composition. Our work shows that, in striking contrast to other eukaryotes, trypanosomes can start nuclear export while the mRNA is still transcribed, but unspliced transcripts remain ‘stuck’ in nuclear pores, probably awaiting processing or decay. Our data indicate that trypanosomes regulate the completion of nuclear export rather than the start. 

INSTRUMENT(S): Q Exactive

ORGANISM(S): Trypanosoma Brucei

SUBMITTER: F Butter  

LAB HEAD: Falk Butter

PROVIDER: PXD010143 | Pride | 2018-10-26

REPOSITORIES: Pride