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SUMMARYSMYB1 is aSchistosoma mansoniprotein highly similar to members of the Y-box binding protein family. Similar to other homologues, SMYB1 is able to bind double- and single-stranded DNA, as well as RNA molecules. The characterization of proteins involved in the regulation of gene expression inS. mansoniis of great importance for the understanding of molecular events that control morphological and physiological changes in this parasite. Here we demonstrate that SMYB1 is located in the cytoplasm of cells from different life-cycle stages ofS. mansoni, suggesting that this protein is probably acting in mRNA metabolism in the cytoplasm and corroborating previous findings from our group that showed its ability to bind RNA. Protein–protein interactions are important events in all biological processes, since most proteins execute their functions through large supramolecular structures. Yeast two-hybrid screenings using SMYB1 as bait identified a partner inS. mansonisimilar to the SmD3 protein ofDrosophila melanogaster(SmRNP), which is important in the assembly of small nuclear ribonucleoprotein complexes. Also, pull-down assays were conducted using immobilized GST-SMYB1 proteins and confirmed the SMYB1-SmRNP interaction. The interaction of SMYB1 with a protein involved in mRNA processing suggests that it may act in processes such as turnover, transport and stabilization of RNA molecules.

SUMMARYAn HMG2-like protein was purified from nuclear extracts of adultSchistosoma mansoni. Investigation of the amino acid composition of the schistosome HMG2-like protein showed that glutamic acid, glycine, aspartic acid and lysine were the most abundant. Carbohydrate analysis showed that the HMG2-like protein presented a low degree of glycosylation, galactose or glucose being the major monosaccharide constituent. Incubation of live schistosomes with32P followed by isolation of nuclear proteins showed that the HMG-2 like protein could be phosphorylated. Partial sequence analysis of cyanogen bromide peptides revealed the occurrence of a phosphorylation consensus motif. The schistosome HMG2-like protein was found to bind preferentially to single-stranded DNA. The results suggest that the major non-histoneS. mansoninuclear protein belongs to the HMG family.