Abstract
RNA-binding proteins (RBPs) participate in several steps of post-transcriptional regulation
of gene expression, such as splicing, messenger RNA transport, mRNA localization, and translation.
Gene-expression regulation in trypanosomatids occurs primarily at the post-transcriptional level, and
RBPs play important roles in the process. Here, we characterized the RBP TcSgn1, which contains
one RNA recognition motif (RRM). TcSgn1 is a close ortholog of yeast Saccharomyces cerevisiae protein
ScSgn1, which plays a role in translational regulation in the cytoplasm. We found that TcSgn1 in
Trypanosoma cruzi is localized in the nucleus in exponentially growing epimastigotes. By performing
immunoprecipitation assays of TcSgn1, we identified hundreds of mRNAs associated with the protein, a
significant fraction of them coding for nucleic acids binding, transcription, and endocytosis proteins. In
addition, we show that TcSgn1 is capable of interacting directly with the poly(A) tail of the mRNAs. The
study of parasites under nutritional stress showed that TcSgn1 was localized in cytoplasmic granules
in addition to localizing in the nucleus. Similar to ScSgn1, we observed that TcSgn1 also interacts
with the PABP1 protein, suggesting that this protein may play a role in regulating gene expression in
T. cruzi. Taken together, our results show that RNA-binding protein TcSgn1 is part of ribonucleoprotein
complexes associated with nuclear functions, stress response, and RNA metabolism.