mRNA encoding a putative RNA helicase of the DEAD-box gene family is up-regulated in trypomastigotes of Trypanosoma cruzi

Differential display of mRNAs from Trypanosoma cruzi epimastigote and metac yclic trypomastigote stages showed several mRNA species differing in their expression level. The cDNA corresponding to one of these mRNAs was used as a probe in Northern blots and identified a RNA product of 2.6 kb with an ex pression level eight or more times higher in trypomastigotes than in epimas tigotes. This probe was also used to screen a genomic library of T. cruzi C L Brener clone prepared in lambda FIX. A clone of about 15 kb was selected that, after partial sequencing, revealed an open reading frame of 688 amino acids encoding a deduced protein with similarity to RNA helicases of the D EAD-box gene family. The presence of the right conserved motifs characteris tic of the DEAD protein family was observed in the T. cruzi sequence, indic ating that it corresponds to a putative RNA helicase gene, which we named H elTc. Southern blot analysis indicated that HelTe is a single-copy gene. Pu lsed-field gel electrophoresis separation of chromosomes of several isolate s of T. cruzi showed that this gene was localized in one or two chromosomal bands.