Poly(A) binding KPAF4/5 complex stabilizes kinetoplast mRNAs in Trypanosoma brucei.

In Trypanosoma brucei, mitochondrial pre-mRNAs undergo 3'-5' exonucleolytic processing, 3' adenylation and uridylation, 5' pyrophosphate removal, and, often, U-insertion/deletion editing. The 3' modifications are modulated by pentatricopeptide repeat (PPR) Kinetoplast Polyadenylation Factors (KPAFs). We have shown that KPAF3 binding to the 3' region stabilizes properly trimmed transcripts and stimulates their A-tailing by KPAP1 poly(A) polymerase.

Pentatricopeptide repeat poly(A) binding protein KPAF4 stabilizes mitochondrial mRNAs in Trypanosoma brucei.

In Trypanosoma brucei, most mitochondrial mRNAs undergo editing, and 3' adenylation and uridylation. The internal sequence changes and terminal extensions are coordinated: pre-editing addition of the short (A) tail protects the edited transcript against 3'-5' degradation, while post-editing A/U-tailing renders mRNA competent for translation. Participation of a poly(A) binding protein (PABP) in coupling of editing and 3' modification processes has been inferred, but its identity and mechanism of action remained elusive.

Differential processing of small RNAs during endoplasmic reticulum stress.

The accumulation of misfolded proteins in the endoplasmic reticulum (ER) lumen due to the disruption of the homeostatic system of the ER leads to the induction of the ER stress response. Cellular stress-induced pathways globally transform genes expression on both the transcriptional and post-transcriptional levels with small RNA involvement as regulators of the stress response. The modulation of small RNA processing might represent an additional layer of a complex stress response program.