CCCH zinc finger proteins (ZC3Hs) are a novel class of RNA-binding protein involved in post-transcriptional mechanisms controlling gene expression. We show TbZC3H20 from Trypanosoma brucei, the causative agent of sleeping sickness and other diseases, stabilizes two developmentally regulated transcripts encoding a mitochondrial carrier protein (MCP12) and trans-sialidase (TS-like E). TbZC3H20 is shown to be an RNA-binding protein that is enriched in insect procyclic form T. brucei and is the first ZC3H discovered controlling gene expression through modulating mRNA abundance in trypanosomes. Previous studies have demonstrated that RNA recognition motif-containing and PUF family RNA-binding proteins can control gene expression by stabilizing specific target mRNA levels. This work is the first to describe a ZC3H stabilizing rather than destabilizing target mRNAs as a regulatory mechanism and the first report of a ZC3H regulating a gene encoding a mitochondrial protein. This suggests a broader role for ZC3Hs in post-transcriptional regulation of gene expression than previously thought.

Background: Eukaryotes typically encode a range of ISWI chromatin remodeling complexes with different functions.Results: We have identified and analyzed three novel ISWI partners in the early branching eukaryote Trypanosoma brucei.Conclusion: T. brucei appears to have a single major ISWI complex.Significance: This unusually simple ISWI configuration could be a consequence of the relative lack of transcriptional regulation in this ancient eukaryote.

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