Differential regulatory role of AU-rich and GU-rich elements in Trypanosoma brucei

Post-transcriptional regulation is the predominant mode of gene expression control in <i>Trypanosoma brucei</i>, yet the underlying regulatory elements and proteins remain poorly defined. AU- and GU-rich elements (AREs and GREs) are common post-transcriptional regulatory motifs. To investigate their roles in <i>T. brucei</i>, we analyzed transcriptomic datasets and extracted 5,840 genes with defined 5' and 3' untranslated regions (UTRs), including 327 that are developmentally regulated between the parasite's two life stages. Computational analysis revealed that AU- and GU-rich elements are widespread and enriched in the 3'UTRs of developmentally regulated mRNAs as well as in transcripts with long half-lives. Functional assays demonstrated regulatory activity of AREs and GREs within the 3'UTRs of five representative genes (<i>ICP</i>, <i>TOP2</i>, <i>MCC</i>-β, <i>PK</i>, and <i>KREPB6</i>), with differential effects on reporter expression. Notably, the GREs in the <i>ICP</i> and <i>TOP2</i> 3'UTRs destabilized reporter transcripts in procyclic-form trypanosomes but enhanced expression in bloodstream forms. RNA pulldown assays further identified DRBD2 as a potential GRE-binding protein, and DRBD2 knockdown reduced <i>ICP</i> mRNA abundance in procyclic trypanosomes. Collectively, these findings demonstrate that AREs and GREs are critical regulatory elements in <i>T. brucei</i>, exhibiting gene-specific and context-dependent functions. Elucidating their regulatory roles and identifying additional binding proteins will provide new insights into the mechanisms of post-transcriptional control in this parasite.