Regulation of a transmembrane protein gene family by the small RNA-binding proteins TbUBP1 and TbUBP2

The loci Tb927.3.4070, 927.3.4080, Tb927.3.4090, 927.3.4100 and 927.3.4110 of Trypanosoma brucei encode five similar proteins with 13–14 transmembrane domains. Corresponding mRNAs are more abundant in bloodstream-form trypanosomes than in procyclics. The 4070, 4090 and 4110 genes have almost identical 3′-intergenic regions and the predicted proteins share a short C-terminal extension; a reporter mRNA with the 4110 3′-untranslated region was more abundant in bloodstream forms than procyclic forms. The 3′-untranslated regions for 4080 and 4100 are different, and that of 4080 gave procyclic-specific reporter expression. TbUBP1 and 2 are proteins with low-specificity RNA-binding activity. Over-expression of TbUBP2 in bloodstream forms increased the overall abundance of mRNA encoding the transmembrane proteins, whereas TbUBP1 and 2 RNA interference decreased it. RNAi targeting TbUBP1 and 2 in bloodstream forms decreased mRNA with a 4110 3′-untranslated region, but increased it for 4080. Thus TbUBP and TbUBP2 may accentuate developmental regulation of the Tb927.3.4070–927.3.4110 mRNAs.