Selective nuclear export of mRNAs is promoted by DRBD18 in Trypanosoma brucei

Area of Science:

• Molecular Biology
• Cell Biology
• Parasitology

Background:

• Gene expression in Kinetoplastids, like Trypanosoma brucei, is mainly regulated post-transcriptionally.
• Nuclear mRNA export is a critical but understudied regulatory step.
• The export factors Mex67/Mtr2 are known to mediate mRNA and tRNA export in T. brucei.

Purpose of the Study:

• To identify RNA binding proteins (RBPs) that regulate mRNA export by influencing Mex67/Mtr2 dynamics.
• To investigate the role of the essential T. brucei RBP, DRBD18, in nuclear mRNA export.

Main Methods:

• In vivo association studies between DRBD18 and Mex67/Mtr2.
• DRBD18 knockdown experiments.
• Transcriptome analysis (whole-cell and cytosol).
• Cross-linking immunoprecipitation (CLIP) experiments.

Main Results:

• DRBD18 directly interacts with Mtr2, a component of the Mex67/Mtr2 export factor.
• DRBD18 depletion causes partial nuclear accumulation of poly(A)+ mRNA, but not tRNAs.
• Knockdown of DRBD18 impairs the nuclear export of a subset of mRNAs.
• DRBD18 binds to specific mRNAs, as shown by CLIP.
• DRBD18 depletion leads to partial nuclear retention of Mex67/Mtr2 export receptors.

Conclusions:

• DRBD18 is a key regulator of selective mRNA nuclear export in T. brucei.
• DRBD18 promotes the mobilization of export-ready messenger ribonucleoprotein complexes (mRNPs) to the cytosol.
• This process involves interaction with Mex67/Mtr2 and facilitates passage through the nuclear pore complex.