A short RNA stem-loop is necessary and sufficient for repression of gene expression during early logarithmic phase in trypanosomes.
Bottom Line: 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.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.
Affiliation: Instituto de Parasitología y Biomedicina 'López-Neyra', IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento, s/n, 18016 Armilla, Granada, Spain.Show MeSH
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Mentions: To study whether the RNA element was sufficient to provide regulation in a different gene context, we modified the luciferase transgene construct to insert the stem–loop 149 nucleotides downstream the luciferase stop codon. As shown in Figure 7A, luciferase activity decreased ∼10-fold in early log phase when the regulatory element was placed into the wild-type actin 3′-UTR. In a second experiment, the stem–loop was inserted within a 3′-UTR derived from the mitochondrial malate dehydrogenase (mMDH) gene, which was not normally regulated during growth cycle (Supplementary Table S1). Cells expressing luciferase fused to wild-type mMDH 3′-UTR showed an activity close to that observed in the actin control cell line (Figure 7A). However, the insertion of the stem–loop within the 3′-UTR of mMDH resulted in a 20-fold decrease in luciferase activity in early log phase.
Affiliation: Instituto de Parasitología y Biomedicina 'López-Neyra', IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento, s/n, 18016 Armilla, Granada, Spain.