Posttranscriptional mechanisms involved in the control of expression of the stage-specific GP82 surface glycoprotein in Trypanosoma cruzi.
Trypanosoma cruzi metacyclic trypomastigotes express the developmentally regulated GP82 glycoprotein, which is implicated in host cell invasion. Although GP82 mRNA and protein are not present and the mRNAs barely detectable in epimastigotes, nuclear run-on analysis showed that it is transcribed in both stages. This result indicates that accumulation of transcripts in metacyclic forms is not due to increased transcription of the GP82 gene. To investigate whether mRNA stability may be responsible for the differences in the steady-state levels of this mRNA, parasites were treated with actinomycin D or cycloheximide. When treated with actinomycin D, the half-lives estimated for GP82 transcripts were about 6h in metacyclic trypomastigotes and 0.5h in epimastigotes. In the presence of cycloheximide, the levels of GP82 mRNA decayed slightly after 8h in metacyclic trypomastigotes, whereas in epimastigotes the levels of this mRNA increased. This effect suggests a stabilizing mechanism acting in metacyclic trypomastigotes and a destabilizing mechanism in epimastigotes which could be mediated by an element present in the 3'-UTR of the transcripts. Consistent with this finding, northern blot analysis showed that GP82 mRNAs were mobilized to polysomes and consequently translated, but only in metacyclic trypomastigotes.
Gentil
Luciana Girotto
LG
Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, UNIFESP, Rua Botucatu, São Paulo, Brazil.
Cordero
Esteban Maurício
EM
do Carmo
Mirian Silva
MS
dos Santos
Márcia Regina Machado
MR
da Silveira
José Franco
JF
D020413:3' Untranslated Regions; D000818:Animals; D005786:Gene Expression Regulation; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D015800:Protozoan Proteins / Q000096:biosynthesis*; D020871:RNA Stability; D014349:Trypanosoma cruzi / Q000235:genetics / Q000502:physiology*; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000096:biosynthesis*
D020413:3' Untranslated Regions; D015800:Protozoan Proteins; D014643:Variant Surface Glycoproteins, Trypanosoma; C527132:glycoprotein GP82, Trypanosoma cruzi