Small-subunit rRNA processome proteins are translationally regulated during differentiation of Trypanosoma cruzi

We used differential display to select genes differentially expressed during differentiation of epimastigotes into metacyclic trypomastigotes in the protozoan parasite Trypanosoma cruzi. One of the selected clones had a sequence similar to that of the small-subunit (SSU) processome protein Sof1p, which is involved in rRNA processing. the corresponding T. cruzi protein, TcSof1, displayed a nuclear localization and is downregulated during metacyclogenesis. Heterologous RNA interference assays showed that depletion of this protein impaired growth but did not affect progression through the cell cycle, suggesting that ribosome synthesis regulation and the cell cycle are uncoupled in this parasite. Quantitative PCR (qPCR) assays of several SSU processome-specific genes in T. cruzi also showed that most of them were regulated posttranscriptionally. This process involves the accumulation of mRNA in the polysome fraction of metacyclic trypomastigotes, where TcSof1 cannot be detected. Metacyclic trypomastigote polysomes were purified and separated by sucrose gradient sedimentation. Northern blot analysis of the sucrose gradient fractions showed the association of TcSof1 mRNA with polysomes, confirming the qPCR data. the results suggest that the mechanism of regulation involves the blocking of translation elongation and/or termination.Inst Biol Mol Parana, BR-81350010 Curitiba, Parana, BrazilFiocruz MS, BR-21040900 Rio de Janeiro, BrazilUniv Fed Rio de Janeiro, Inst Biofis Carlos Chagas Filho, BR-21949900 Rio de Janeiro, BrazilUniversidade Federal de São Paulo, Dept Microbiol Imunol & Parasitol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Microbiol Imunol & Parasitol, BR-04023062 São Paulo, BrazilWeb of Scienc