Pathways of mRNA decay in trypanosomes

Messenger RNA (mRNA) decay is a central determinant of gene expression in eukaryotes, functioning both as a quality control mechanism and as a regulatory layer that shapes transcript abundance. In trypanosomes, including Trypanosoma brucei, gene expression relies almost entirely on post-transcriptional mechanisms due to polycistronic transcription and the near absence of promoter-specific transcriptional regulation. As a result, mRNA stability plays a dominant role in controlling protein output and developmental gene expression programs. In this review, we summarize current knowledge of the major nuclear and cytoplasmic mRNA decay pathways and surveillance mechanisms operating in T. brucei, highlighting both conserved and parasite-specific features of the RNA degradation machinery. We discuss the roles of the principal exonucleases, as well as deadenylation and decapping processes, and outline proposed strategies for mRNA stabilization and destabilization. Despite significant progress, direct mechanistic links between cis-regulatory elements, RNA-binding proteins, and specific decay pathways remain poorly understood. We conclude by outlining key open questions and emerging experimental approaches that promise to advance our understanding of mRNA decay as a central regulatory axis in trypanosome biology.