Discussion

RNA polymerase I from trypanosomes has raised the interest of several colleagues in the field of molelcular parasitology, especially in the case of African species of trypanosomes where this enzymatic complex transcribes the well-studied variant surface glycoprotein encoding genes, in addition to rRNA transcription units.  Our research work group has been interested in the analysis of rRNA genes transcription in the American species Trypanosoma cruzi.  In a recent line of research we are conducting the general characterization of the orthologous RNA pol I subunit TcRPA31.  The deduced primary structure of this protein shows the occurrence of a potential nuclear localization signal (NLS).  With the aid of a tagged fluorescent version of this protein, we have been able to demonstrate its nucleolar localization in transfected T. cruzi cells.  A deletion of the referred NLS in the transfected chimeric genes, produced a fluorescent protein present throughout the cellular body of the parasites.  Therefore, we conclude that this NLS is functional in T. cruzi, thus providing an experimental marker to further analyze the import of proteins in this pathogen.