NUCLEOLAR RELOCALIZATION OF RBPs INDUCED BY TRANSCRIPTIONAL STRESS IN T. cruzi

NAZER EZEQUIEL; SANCHEZ DANIEL

Bariloche Provincia de Rio Negro Argentina

Simposio; Gene Expression and RNA Processing-Cell Biology, Signaling and Alternative Splicing; 2007

ICGEB Meeting and EURASNET Symposium

TcSR62 is a RNA Binding Protein (RBP) from Trypanosoma cruzi belonging to the SR-related RBP family. SR and SR-related proteins have multiple roles in mRNA metabolism, particularly as regulators of pre-mRNA splicing.. TcSR62 localizes mainly to the cell nucleus in a speckled pattern, and it is also present, although in lesser amount, in the cytoplasm in a fine punctuated pattern.Taking into account that TcSR62 and its orthologue in T. brucei (RRM1) have been putatively implicated in cell cycle/differentiation and that the parasite?s differentiation might be trigger by different environmental conditions we were interested in studying TcSR62 behavior under stress conditions. In this work we found that TcSR62 as well as other nuclear or cytoplasmic RBPs, such as TcPABP (Poly-A Binding Protein) and TcPTB (Polypyrimidine Tract Binding Protein), were re-localized to the nucleolus under transcriptional inhibition treatment but not by other stress conditions. In addition, inhibition of pre-mRNA trans-splicing by sinefungine could not promote RBPs nucleolar re-localization.We also showed that the nucleolar localization response was markedly reduced by ATP depletion, and phosphorylation inhibition, suggesting that this process involves an active transport mechanism.Interestingly, stress-induced nucleolar re-localization of RBPs was induced in a stage- specific manner, being evident in the replicative non-infective forms (epimastigote and amastigote) but not in the non-replicate infective form (trypomastigote).These results provide the first evidence stress-induced nucleolar trafficking of RBPs in an ancient eukaryotic cell under a particular stress condition.