Trypanosome RACK1: protein-protein liaisons and gene functional assays.

NYAMBEGA B., JURI AYUB M., CURTO M.A., BERCOVICH N., MASIGA D., LONGHI S.A.,

Mendoza, Argentina

Congreso; VII CongresoArgentina de Protozoología y Enfermedades Parasitarias,; 2005

Sociedad Argentina de Protozoología

Recent investigations on T. cruzi 80S ribosome have shed light onto structural differences to the eukaryotic ribosome. Notably, the absence of receptor for activated protein kinase C 1 (RACK1) on the T. cruzi 40S and its presence on the yeast 40S subunit particle at the vicinity of ribosomal proteins rpS3, rpS5, rpS16, rpS20 and poised to interact with 18S ribosomal RNA (rRNA) helices H39 and H40. Sequence analyses between T. cruzi proteins and rRNAs neighboring RACK1 reveal striking differences which we think could account for RACK1´s absence on the T. cruzi ribosome. These include stretches of insertions on the 5 prime 18S rRNA sequences and amino acid deletions spanning rpS3 C-terminal and rpS5 N-terminal sequence regions. RACK1 gene is present in the trypanosome genome and proteome, raising questions as to its exact role in TriTryps. Given its potential role in eukaryotic trans lation initiation and mRNA processing, we investigated likely protein-protein interactions involving T. cruzi and T. brucei RACK1. Preliminary results show RACK1 does not directly contact the proteins involved in Trans-spliceosome assembly. RNA interference studies (performed with classical and novel vectors including trypanosome artificial chromosomes) suggest an essential role of RACK1 in African trypanosomes.