ZFP36 or tristetraprolin (TTP) is a member of the family of zinc finger proteins; ZFP36 was first identified as a gene that was rapidly induced by the stimulation of fibroblasts with growth factors and mitogens. Native human TTP expressed in neutrophils, lymphocytes, and monocytes is primarily cytoplasmic, and this protein is highly phosphorylated in vivo. TTP is an mRNA binding protein; it binds to AU-rich elements in mRNA and removes the poly(A) tail, consequently increasing the rate of mRNA turnover. The most characterized gene regulated by TTP is the AU-rich tumor necrosis factor alpha (TNF-alpha) gene. TTP binds to the AU-rich element (ARE) in the 3′ UTR of TNF mRNA, and regulates the rate of TNF mRNA turnover in vivo. Recent studies showed that polyA-binding protein 1 (PABP1) inhibits the degradation of the TNF poly(A) tail by TTP.