INVESTIGADORES
CARRILLO Carolina
congresos y reuniones científicas
Título:
Trypanosoma cruzi as a model system to study the expression of exogenous genes coding for polyamine-biosynthetic enzymes
Autor/es:
ALGRANATI ID; CARRILLO C; GONZALEZ NS
Lugar:
Waterville Valley, NH
Reunión:
Conferencia; Gordon Research Conference on Polyamines; 2007
Institución organizadora:
Gordon Research
Resumen:
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Trypanosoma cruzi as a
model system to study the expression of exogenous genes coding for
polyamine-biosynthetic enzymes.
Trypanosoma
cruzi is the only eukaryotic cell unable to
syntesize polyamines de novo because its
genome contains neither ornithine decarboxilase (ODC) nor arginine
decarboxylase (ADC) genes, presumably lost during evolution. Since T. cruzi behaves as a natural deletion
mutant for ODC and ADC genes, we have used this parasite as a model system to
study the regulation of a heterologous ODC gene expression. Transgenic T. cruzi obtained after transformation
of wild type parasites with a recombinanat plasmid containing the ODC-coding
region from Crithidia fasciculata
became autotrophic for putrescine and at the same time susceptible to DFMO, an
irreversible inhibitor of ODC.
We have studied the emergence of
DFMO-resistant T. cruzi after one.step selection of ODC-transformed parasites
cultivated in the presence of high levels of the drug. Our results have
indicated a duplication of the ODC-gene copy number in the drug-resistant cell
line. The ODC transcripts and the corresponding translation products showed
very significant increases (about 7 and 25-fold, respectively) in DFMO-
resistant parasites, while the ODC enzymatic activity was only 5 times higher
than in drug-sensitive T. cruzi. The
unequal increases of ODC-protein and enzymatic activity in DFMO-resistant protozoa strongly suggest that in addition to
gene amplification and enhaced transcription and translation, the assembly of
ODC-polypeptide chains into dimeric active enzyme molecules might also
contribute to regulate the ODC-gene expression and the level of
DFMO-resistance.