Interactions of CCCH Zinc Finger Proteins with mRNA

• Published in: The Journal of biological chemistry 2000-06, Vol.275 (23), p.17827-17837
• Main Authors: Lai, Wi S., Carballo, Ester, Thorn, Judith M., Kennington, Elizabeth A., Blackshear, Perry J.
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M001696200

Macrophages derived from tristetraprolin (TTP)-deficient mice exhibited increased tumor necrosis factor α (TNFα) release as a consequence of increased stability of TNFα mRNA. TTP was then shown to destabilize TNFα mRNA after binding directly to the AU-rich region (ARE) of the 3′-untranslated region of the TNFα mRNA. In mammals and in Xenopus, TTP is the prototype of a small family of three known zinc finger proteins containing two CCCH zinc fingers spaced 18 amino acids apart; a fourth more distantly related family member has been identified inXenopus and fish. We show here that representatives of all four family members were able to bind to the TNFα ARE in a cell-free system and, in most cases, promote the breakdown of TNFα mRNA in intact cells. Because the primary sequences of these CCCH proteins are most closely related in their tandem zinc finger domains, we tested whether various fragments of TTP that contained both zinc fingers resembled the intact protein in these assays. We found that amino- and carboxyl-terminal truncated forms of TTP, as well as a 77 amino acid fragment that contained both zinc fingers, could bind to the TNFα ARE in cell-free cross-linking and gel shift assays. In addition, these truncated forms of TTP could also stimulate the apparent deadenylation and/or breakdown of TNFα mRNA in intact cells. Alignments of the tandem zinc finger domains from all four groups of homologous proteins have identified invariant residues as well as group-specific signature amino acids that presumably contribute to ARE binding and protein-specific activities, respectively.