Abstract
We have compared the transcriptomes of cultured procyclic Trypanosoma brucei cells in early and late logarithmic phases and found that ∼200 mRNAs were differentially regulated. In late log phase cells, the most upregulated mRNA encoded the nucleobase transporter NT8. The 3′ untranslated region (UTR) of NT8 contains a short stem–loop cis-element that is necessary for the regulation of NT8 expression in response to external purine levels. When placed in the 3′-UTR of an unregulated transcript, the cis-element is sufficient to confer regulation in response to purines. To our knowledge, this is the first example of a discrete RNA element that can autonomously regulate gene expression in trypanosomes in response to an external factor and reveals an unprecedented purine-dependent signaling pathway that controls gene expression in eukaryotes.
Highlights
Coordinating expression of functionally-related genes in response to environmental signals is essential for a cell
There was no significant enrichment for any Gene Ontology (GO) category in the downregulated messenger RNAs (mRNAs) set
We have used high-throughput sequencing to analyze how trypanosomes remodel their transcriptome when entering in late logarithmic phase, and obtain valuable information that could be used to identify novel cis- and transacting factors involved in post-transcriptional regulation
Summary
Coordinating expression of functionally-related genes in response to environmental signals is essential for a cell. In spite of the dependence on post-transcriptional mechanisms, very few RNA-binding proteins have been characterized in detail in trypanosomatids, and in even fewer instances precisely defined cis-acting elements have been unequivocally identified as being necessary and sufficient to confer regulation [5,8] These include a 26-mer stem–loop within T. brucei EP1 procyclin that causes RNA instability in the bloodstream form [9], a 25-nt glycerol-responsive element in the T. brucei GPEET procyclin that controls expression by glucose and during development in the insect vector [10], a 50nt AU-rich region within mucin genes in T. cruzi that affects mRNA degradation and translation [11] and a 34-nt element that represses expression in proliferative T. brucei slender bloodstream forms and activates it in quiescent stumpy bloodstream parasites [12]. In Leishmania major, a retroposon-derived sequence of ∼600 nt located within the 3 -UTR of many transcripts,
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