Distinct 3'-untranslated region elements regulate stage-specific mRNA accumulation and translation in Leishmania.
We recently characterized a large developmentally regulated gene family in Leishmania encoding the amastin surface proteins. While studying the regulation of these genes, we identified a region of 770 nucleotides (nt) within the 2055-nt 3'-untranslated region (3'-UTR) that regulates stage-specific gene expression at the level of translation. An intriguing feature of this 3'-UTR regulatory region is the presence of a approximately 450-nt element that is highly conserved among several Leishmania mRNAs. Here we show, using a luciferase reporter system and polysome profiling experiments, that the 450-nt element stimulates translation initiation of the amastin mRNA in response to heat shock, which is the main environmental change that the parasite encounters upon its entry into the mammalian host. Deletional analyses depicted a second region of approximately 100 nucleotides located at the 3'-end of several amastin transcripts, which also activates translation in response to elevated temperature. Both 3'-UTR regulatory elements act in an additive manner to stimulate amastin mRNA translation. In addition, we show that acidic pH encountered in the phagolysosomes of macrophages, the location of parasitic differentiation, triggers the accumulation of amastin transcripts by a distinct mechanism that is independent of the 450-nt and 100-nt elements. Overall, these important findings support the notion that stage-specific post-transcriptional regulation of the amastin mRNAs in Leishmania is complex and involves the coordination of distinct mechanisms controlling mRNA stability and translation that are independently triggered by key environmental signals inducing differentiation of the parasite within macrophages.
McNicoll
François
F
Infectious Diseases Research Center, Centre Hospitalier de l'Université Laval Research Center of Laval University, Quebec G1V 4G2, Canada.
Müller
Michaela
M
Cloutier
Serge
S
Boilard
Nathalie
N
Rochette
Annie
A
Dubé
Marthe
M
Papadopoulou
Barbara
B
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D000818:Animals; D015152:Blotting, Northern; D002454:Cell Differentiation; D002499:Centrifugation, Density Gradient; D004247:DNA / Q000737:chemistry; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D005822:Genetic Vectors; D006863:Hydrogen-Ion Concentration; D018314:Leishmania infantum / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D008247:Lysosomes / Q000737:chemistry; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D008957:Models, Genetic; D016366:Open Reading Frames; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism*; D015398:Signal Transduction; D013395:Sucrose / Q000494:pharmacology; D014158:Transcription, Genetic; D014162:Transfection
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D012333:RNA, Messenger; D013395:Sucrose; D004247:DNA; D008156:Luciferases