The Trypanosoma cruzi nucleic acid binding protein Tc38 presents changes in the intramitochondrial distribution during the cell cycle

María A Duhagon,Leticia Pérez-Díaz,Noreen Williams,Bruno Dallagiovanna,Dante Maugeri,Lucía Pastro,Beatriz Garat,Sheila C Nardelli,José R Sotelo-Silveira,Sergio Schenkman

doi:10.1186/1471-2180-9-34

Abstract

BackgroundTc38 of Trypanosoma cruzi has been isolated as a single stranded DNA binding protein with high specificity for the poly [dT-dG] sequence. It is present only in Kinetoplastidae protozoa and its sequence lacks homology to known functional domains. Tc38 orthologues present in Trypanosoma brucei and Leishmania were proposed to participate in quite different cellular processes. To further understand the function of this protein in Trypanosoma cruzi, we examined its in vitro binding to biologically relevant [dT-dG] enriched sequences, its expression and subcellular localization during the cell cycle and through the parasite life stages.ResultsBy using specific antibodies, we found that Tc38 protein from epimastigote extracts participates in complexes with the poly [dT-dG] probe as well as with the universal minicircle sequence (UMS), a related repeated sequence found in maxicircle DNA, and the telomeric repeat. However, we found that Tc38 predominantly localizes into the mitochondrion. Though Tc38 is constitutively expressed through non-replicating and replicating life stages of T. cruzi, its subcellular localization in the unique parasite mitochondrion changes according to the cell cycle stage. In epimastigotes, Tc38 is found only in association with kDNA in G1 phase. From the S to G2 phase the protein localizes in two defined and connected spots flanking the kDNA. These spots disappear in late G2 turning into a diffuse dotted signal which extends beyond the kinetoplast. This later pattern is more evident in mitosis and cytokinesis. Finally, late in cytokinesis Tc38 reacquires its association with the kinetoplast. In non-replicating parasite stages such as trypomastigotes, the protein is found only surrounding the entire kinetoplast structure.ConclusionsThe dynamics of Tc38 subcellular localization observed during the cell cycle and life stages support a major role for Tc38 related to kDNA replication and maintenance.

Highlights

Tc38 of Trypanosoma cruzi has been isolated as a single stranded DNA binding protein with high specificity for the poly [dT-dG] sequence
We employed a purified polyclonal antiserum raised against the recombinant GSTTc38 protein that recognizes a main band with an apparent molecular weight of about 38 kDa in total protein extracts of epimastigotes
Tc38 is expressed throughout T. cruzi life cycle In order to better understand the Tc38 physiological role, we looked at its expression in both proliferative and non-proliferative stages of the parasite

Summary

Introduction

Tc38 of Trypanosoma cruzi has been isolated as a single stranded DNA binding protein with high specificity for the poly [dT-dG] sequence. It is present only in Kinetoplastidae protozoa and its sequence lacks homology to known functional domains. A different role was previously assigned for this protein This protein ( named TbRBP38) and the Leishmania tarentolae orthologue (LtRBP38) were proposed as mitochondrial RNA binding proteins involved in non-specific modulation of mitochondrial RNA stability [11]. We reported the isolation of the T. cruzi orthologue (Tc38) from nuclear enriched fractions [12] We demonstrated that this protein has single stranded DNA binding abilities and that it shows a preferential binding to poly [dT-dG] sequences. Later it was suggested that the potential LaGT2 targets may not be restricted to telomere sequences [14]

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Conclusion