Members of the Tristetraprolin Family of Tandem CCCH Zinc Finger Proteins Exhibit CRM1-dependent Nucleocytoplasmic Shuttling

Abstract

Members of the tristetraprolin (TTP) family of CCCH tandem zinc finger proteins can bind directly to certain types of AU-rich elements (AREs) in mRNA. Experiments in TTP-deficient mice have shown that TTP is involved in the physiological destabilization of at least two cytokine mRNAs, those encoding tumor necrosis factor ␣ and granulocyte-macrophage colony-stimulating factor. The two other known mammalian members of the TTP family, CMG1 and TIS11D, also contain AREbinding CCCH tandem zinc finger domains and can also destabilize ARE-containing mRNAs. To investigate the effects of primary sequence on the subcellular localization of these proteins, we constructed green fluorescent protein fusions with TTP, CMG1, and TIS11D; these were predominantly cytoplasmic when expressed in 293 or HeLa cells. Deletion and mutation analyses revealed functional nuclear export signals in the amino terminus of TTP and in the carboxyl termini of CMG1 and TIS11D. This type of leucine-rich nuclear export signal interacts with the nuclear export receptor CRM1; abrogation of CRM1 activity resulted in nuclear accumulation of TTP, CMG1, and TIS11D. These proteins are thus nucleocytoplasmic shuttling proteins and rely on CRM1 for their export from the nucleus. Although TTP, CMG1, and TIS11D lack known nuclear import sequences, mapping experiments revealed that their nuclear accumulation required an intact tandem zinc finger domain but did not require RNA binding ability. These findings suggest possible roles for nuclear import and export in the regulation of cellular TTP, CMG1, and TIS11D activity.

The Drosophila Tis11 Protein and Its Effects on mRNA Expression in Flies

“…There is also a highly conserved region near the extreme C terminus (green). The conserved C-terminal region in mammalian ZFP36L1 and ZFP36L2 is known to contain an active nuclear export sequence (7,47). Recent studies in Drosophila 2) with the corresponding proteins assembled from Bombyx mori (XP_004928274) and Tribolium castaneum (XP_968440).…”

CYFIP2, a Direct p53 Target, is Leptomycin-B Sensitive

“…Localization of TIS11D, a known LMB-sensitive nucleocytoplasmic shuttling mRNA binding protein served as a positive control (published in ). 10,19 As expression levels increase, however, GFP-CYFIP2 tends to cluster into cytoplasmic punctate speckles that can further coalesce into perinuclear protein aggregates (Fig. 5B).…”

Arthritis suppressor genes TIA-1 and TTP dampen the expression of tumor necrosis factor α, cyclooxygenase 2, and inflammatory arthritis

“…Many mRNAs that encode inf lammatory mediators (e.g., TNF-␣, IL-1␤, COX-2, and matrix metalloproteases) possess AREs in their 3Ј untranslated regions that inhibit translation and promote mRNA decay (19,21,22). These functional effects require the coordinated activity of ARE-BPs such as TIA-1 and TTP (10,23).…”