Identification and Stage-specific Association with the Translational Apparatus of TbZFP3, a CCCH Protein That Promotes Trypanosome Life-cycle Development

Keith Matthews,Athina Paterou,Paul Craddy,Katelyn Fenn,Pegine Walrad

doi:10.1074/jbc.m604280200

Abstract

The post-transcriptional control of gene expression is becoming increasingly important in the understanding of regulated events in eukaryotic cells. The parasitic kinetoplastids have a unique reliance on such processes, because their genome is organized into polycistronic transcription units in which adjacent genes are not coordinately regulated. Indeed, the number of RNA-binding proteins predicted to be encoded in the genome of kinetoplastids is unusually large, invoking the presence of unique RNA regulators dedicated to gene expression in these evolutionarily ancient organisms. Here, we report that a small CCCH zinc finger protein, TbZFP3, enhances development between life-cycle stages in Trypanosoma brucei. Moreover, we demonstrate that this protein interacts both with the translational machinery and with other small CCCH proteins previously implicated in trypanosome developmental control. Antibodies to this protein also co-immunoprecipitate EP procyclin mRNA and encode the major surface antigen of insect forms of T. brucei. Strikingly, although TbZFP3 is constitutively expressed, it exhibits developmentally regulated association with polyribosomes, and mutational analysis demonstrates that this association is essential for the expression of phenotype. TbZFP3 is therefore a novel regulator of developmental events in kinetoplastids that acts at the level of the post-transcriptional control of gene expression.

Highlights

Regulatory events in prokaryotic and eukaryotic organisms are most commonly governed by transcriptional control
Transcriptional control has only been observed for two protein-coding transcription units in T. brucei: those encoding the variant surface glycoprotein gene and procyclin genes, which encode a protein coat on the forms of the parasite found in its tsetse fly vector
To address whether TbZFP3 is regulated during the parasite life cycle, we examined the mRNA and protein levels for this gene in bloodstream and procyclic forms

Summary

Introduction

Regulatory events in prokaryotic and eukaryotic organisms are most commonly governed by transcriptional control. A related protein, TbZFP2, generates a procyclic stage-specific morphological phenotype when overexpressed and is required in bloodstream forms for efficient differentiation, as revealed by transcript-specific RNAi3 [16].

Results

Conclusion