Putative DEAD and DExH-box RNA helicases families in Entamoeba histolytica.

RNA helicases catalyze the unwinding of double-stranded RNA structures to perform numerous genetic processes. These enzymes are characterized by the presence of a conserved helicase domain with specific helicases motifs whose amino acid sequence allows the differentiation between DEAD and DExH-box RNA helicase families. Taking advantage of the availability of the complete genome sequence of Entamoeba histolytica, the protozoan responsible for human amoebiasis, we have performed a genomic survey for DEAD and DExH-box RNA helicases encoding genes in this organism. By extensive in silico analysis, we identified 20 EhDEAD and 13 EhDExH-box RNA helicases, which contain almost all the conserved helicase motifs. Additionally, several EhDEAD and EhDExH proteins present specific N- and C-terminal domains that could be related to subcellular localization or function. Phylogenetic studies and sequences analysis suggested that this large EhDEAD/DExH-box RNA helicases family has been generated by gene or internal regions duplication, mutation events, introns formation and motif deletions. Interestingly, EhDexh1 and EhDeaxh10 genes seem to be formed by gene fusion of two ancestral bacterial genes, a mechanism that appears to be evolutionary conserved in the eukaryotic lineage of orthologous proteins. Finally, RT-PCR assays, microarrays and proteomics data analysis showed that several EhDead are differentially expressed in relation to distinct culture conditions. These computational and experimental data provide new information on the evolution of EhDEAD/EhDExH-box RNA helicases and their potential relevance for RNA metabolism in E. histolytica.

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