RIP-chip analysis of Tino/hMEX-3D mRNPs

Tino is an A+U-Rich Element (ARE) binding protein first identified through its ability to bind to bcl-2 mRNA and to contribute to its degradation. It has recently been recognized as a shorter form of the human Mex-3D protein (hMex-3D), one of the four members of the family of Mex-3 RNA-binding phosphoproteins. In C. elegans, ceMex-3 is a translational regulator that plays a key role in early embryonic development and in the maintenance of worm germ line totipotency. To examine the potential functional conservation between ceMex-3 and hMex3, we have used complementary microarray-based approaches to identify mRNAs directly bound to Tino/hMex-3D. Computational analysis of these target mRNAs resulted in the identification of an U-rich, 34- to 39-nucleotide long, consensus, forming loops of variable sizes. Remarkably, more than half of Tino/hMex-3D targets also contain the consensus for Quaking, which is the human ortholog of GLD-1, a regulator of nematode gametogenesis. All together, our results suggest that Tino/hMex-3D belongs to a regulatory circuit of mRNA trans-acting factors involved in cell fate and differentiation.

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