The human TTP protein: sequence, alignment with related proteins, and chromosomal localization of the mouse and human genes

Activation of clg, a novel dbl family guanine nucleotide exchange factor gene, by proviral insertion at evi24, a common integration site in B cell and myeloid leukemias

Retroviruses induce leukemia in inbred strains of mice by activating cellular proto-oncogenes and/or inactivating tumor suppressors. The proviral integration sites in these leukemias provide powerful genetic tags for disease gene identification. Here we show that Evi24, a common site of retroviral integration in AKXD B cell and BXH-2 myeloid leukemias, contains a novel Dbl family guanine nucleotide exchange factor gene. We have designated this gene Clg (common-site lymphoma/leukemia guanine nucleotide exchange factor). Proviral integrations on chromosome 7 at Evi24 are located 7.6-10.3 kb upstream of Clg and increased Clg expression 2-5-fold compared with leukemias lacking proviral integrations at Evi24. Clg contains Dbl/pleckstrin homology domains with substantial sequence homology to many Rho family activators, including the transforming Dbl and Dbs/Ost oncogenes. Nucleotide exchange assays indicated that Clg specifically activated nucleotide exchange on Cdc42, but not RhoA or Rac1, in vitro. NIH 3T3 transfection studies showed that overexpression of full-length and carboxyl-terminally truncated forms of Clg morphologically transformed NIH 3T3 cells. This study and studies showing that the human homolog of EVI24 is located in a region of 19q13 frequently amplified in B cell lymphomas and pancreatic and breast cancers implicate Clg and Cdc42 activation in mouse and human cancers.

Members of the tristetraprolin family of tandem CCCH zinc finger proteins exhibit CRM1-dependent nucleocytoplasmic shuttling

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 alpha and granulocyte-macrophage colony-stimulating factor. The two other known mammalian members of the TTP family, CMG1 and TIS11D, also contain ARE-binding 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.

Transcriptional activation function of zinc finger protein TIS11 and its negative regulation by phorbol ester

TIS11, a CCCH zinc finger protein, is one of the typical growth factor-inducible nuclear proteins. We found that TIS11 possesses the potential to activate transcription when fused to the GAL4 DNA binding domain and transiently cotransfected into rat pheochromocytoma PC12 cells along with a GAL4-responsive luciferase reporter gene. The study with deletion mutants of TIS11 revealed that the major transactivation region is located at the N-terminal 101 amino acid residues and that the remaining central and C-terminal region had a moderate transactivational activity. In addition, the transactivational activity of TIS11 was found to be significantly reduced by treating the transfectants with phorbol 12-myristate 13-acetate (PMA). PMA-induced inactivation of TIS11 was blocked by calphostin C, a protein kinase C inhibitor, and PD98059, a mitogen-activated protein (MAP) kinase kinase inhibitor. These results suggested that TIS11 functions as a positive transcriptional regulator and that the protein kinase C/MAP kinase signaling cascade is involved in negative regulation of TIS11 by PMA.

Interactions of CCCH zinc finger proteins with mRNA. Binding of tristetraprolin-related zinc finger proteins to Au-rich elements and destabilization of mRNA

Macrophages derived from tristetraprolin (TTP)-deficient mice exhibited increased tumor necrosis factor alpha (TNFalpha) release as a consequence of increased stability of TNFalpha mRNA. TTP was then shown to destabilize TNFalpha mRNA after binding directly to the AU-rich region (ARE) of the 3'-untranslated region of the TNFalpha 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 in Xenopus and fish. We show here that representatives of all four family members were able to bind to the TNFalpha ARE in a cell-free system and, in most cases, promote the breakdown of TNFalpha 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 TNFalpha 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 TNFalpha 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.

Evidence that tristetraprolin is a physiological regulator of granulocyte-macrophage colony-stimulating factor messenger RNA deadenylation and stability

Deficiency of tristetraprolin (TTP), the prototype of the CCCH zinc finger proteins, results in a complex inflammatory syndrome in mice. Most aspects of the syndrome are secondary to excess circulating tumor necrosis factor (TNF)–, a consequence of increased stability of TNF- messenger RNA (mRNA) in TTP-deficient macrophages. TTP can bind directly to the AU-rich element in TNF- mRNA, increasing its lability. Here we show that TTP deficiency also results in increased cellular production of granulocyte-macrophage colony–stimulating factor (GM-CSF) and increased stability of its mRNA, apparently secondary to decreased deadenylation. Similar findings were observed in mice also lacking both types of TNF- receptors, excluding excess TNF- production as a cause of the increased GM-CSF mRNA levels and stability. TTP appears to be a physiological regulator of GM-CSF mRNA deadenylation and stability.

Genetic mapping of the Camurati-Engelmann disease locus to chromosome 19q13.1-q13.3

Camurati-Engelmann disease (CED [MIM 131300]), or progressive diaphyseal dysplasia, is an autosomal dominant sclerosing bone dysplasia characterized by progressive bone formation along the periosteal and endosteal surfaces at the diaphyseal and metaphyseal regions of long bones and cranial hyperostosis, particularly at the skull base. The gene for CED, or its chromosomal localization, has not yet been identified. We performed a genomewide linkage analysis of two unrelated Japanese families with CED, in which a total of 27 members were available for this study; 16 of them were affected with the disease. Two-point linkage analysis revealed a maximum LOD score of 7.41 (recombination fraction.00; penetrance 1.00) for the D19S918 microsatellite marker locus. Haplotype analysis revealed that all the affected individuals shared a common haplotype observed, in each family, between D19S881 and D19S606, at chromosome 19q13.1-q13.3. These findings, together with a genetic distance among the marker loci, indicate that the CED locus can be assigned to a 15.1-cM segment between D19S881 and D19S606.

Evidence that tristetraprolin binds to AU-rich elements and promotes the deadenylation and destabilization of tumor necrosis factor alpha mRNA

Mice deficient in tristetraprolin (TTP), the prototype of a family of CCCH zinc finger proteins, develop an inflammatory syndrome mediated by excess tumor necrosis factor alpha (TNF-alpha). Macrophages derived from these mice oversecrete TNF-alpha, by a mechanism that involves stabilization of TNF-alpha mRNA, and TTP can bind directly to the AU-rich element (ARE) in TNF-alpha mRNA (E. Carballo, W. S. Lai, and P. J. Blackshear, Science 281:1001-1005, 1998). We show here that TTP binding to the TNF-alpha ARE is dependent upon the integrity of both zinc fingers, since mutation of a single cysteine residue in either zinc finger to arginine severely attenuated the binding of TTP to the TNF-alpha ARE. In intact cells, TTP at low expression levels promoted a decrease in size of the TNF-alpha mRNA as well as a decrease in its amount; at higher expression levels, the shift to a smaller TNF-alpha mRNA size persisted, while the accumulation of this smaller species increased. RNase H experiments indicated that the shift to a smaller size was due to TTP-promoted deadenylation of TNF-alpha mRNA. This CCCH protein is likely to be important in the deadenylation and degradation of TNF-alpha mRNA and perhaps other ARE-containing mRNAs, both in normal physiology and in certain pathological conditions.

Identification of four CCCH zinc finger proteins in Xenopus, including a novel vertebrate protein with four zinc fingers and severely restricted expression

Tristetraprolin (TTP), the prototype of a class of CCCH zinc finger proteins, is a phosphoprotein that is rapidly and transiently induced by growth factors and serum in fibroblasts. Recent evidence suggests that a physiological function of TTP is to inhibit tumor necrosis factor alpha secretion from macrophages by binding to and destabilizing its mRNA (Carballo, E., Lai, W.S., Blackshear, P.J., 1998. Science, 281, 1001-1005). To investigate possible functions of CCCH proteins in early development of Xenopus, we isolated four Xenopus cDNAs encoding members of this class. Based on 49% overall amino acid identity and 84% amino acid identity within the double zinc finger domain, one of the Xenopus proteins (XC3H-1) appears to be the homologue of TTP. By similar analyses, XC3H-2 and XC3H-3 are homologues of ERF-1 (cMG1, TIS11B) and ERF-2 (TIS11D). A fourth protein, XC3H-4, is a previously unidentified member of the CCCH class of vertebrate zinc finger proteins; it contains four Cx8Cx5Cx3H repeats, two of which are YKTEL Cx8Cx5Cx3H repeats that are closely related to sequences found in the other CCCH proteins. Whereas XC3H-1, XC3H-2, and XC3H-3 were widely expressed in adult tissues, XC3H-4 mRNA was not detected in any of the adult tissues studied except for the ovary. Its expression appeared to be limited to the ovary, oocyte, egg and the early embryonic stages leading up to the mid-blastula transition. Its mRNA was highly expressed in oocytes of all ages, and was enriched in the animal pole cytosol of mature oocytes. Maternal expression was also seen with the other three messages, suggesting the possibility that these proteins are involved in regulating mRNA stability in oocyte maturation and/or early embryogenesis.

Feedback inhibition of macrophage tumor necrosis factor-alpha production by tristetraprolin

Tumor necrosis factor-alpha (TNF-alpha) is a major mediator of both acute and chronic inflammatory responses in many diseases. Tristetraprolin (TTP), the prototype of a class of Cys-Cys-Cys-His (CCCH) zinc finger proteins, inhibited TNF-alpha production from macrophages by destabilizing its messenger RNA. This effect appeared to result from direct TTP binding to the AU-rich element of the TNF-alpha messenger RNA. TTP is a cytosolic protein in these cells, and its biosynthesis was induced by the same agents that stimulate TNF-alpha production, including TNF-alpha itself. These findings identify TTP as a component of a negative feedback loop that interferes with TNF-alpha production by destabilizing its messenger RNA. This pathway represents a potential target for anti-TNF-alpha therapies.

Characteristics of the intron involvement in the mitogen-induced expression of Zfp-36

Zfp-36, the gene encoding the putative zinc finger protein tristetraprolin (TTP), is rapidly induced in fibroblasts by a variety of growth factors. Recent gene knockout experiments have shown that TTP-deficient mice developed arthritis, cachexia, and autoimmunity, all apparently mediated by an excess of tumor necrosis factor alpha. We recently showed that full serum inducibility of Zfp-36 requires elements in the promoter; in addition, removal of the single intron strikingly inhibited serum-induced TTP expression. We show here that replacement of the intron with unrelated sequences, or removal of 95% of the intron but retention of the splice sites, each resulted in the maintenance of approximately 45 and 19%, respectively, of full serum-induced expression. In addition, deletion of intron sequences base pairs 601-655 decreased the serum-induced expression of TTP by 65%. Sequence base pairs 618-626 bound specifically to the transcription factor Sp1; mutation of this binding motif decreased TTP expression by 70%, suggesting that Sp1 binding to this motif contributes to serum induction of Zfp-36. We conclude that full serum-induced expression of Zfp-36 depends on the activation of conventional promoter elements as well as elements in the single intron, and that the presence per se of the intron in its natural location also contributes significantly to the regulated expression of this gene.

muscleblind, a gene required for photoreceptor differentiation in Drosophila, encodes novel nuclear Cys3His-type zinc-finger-containing proteins

We have isolated the embryonic lethal gene muscleblind (mbl) as a suppressor of the sev-svp2 eye phenotype. Analysis of clones mutant for mbl during eye development shows that it is autonomously required for photoreceptor differentiation. Mutant cells are recruited into developing ommatidia and initiate neural differentiation, but they fail to properly differentiate as photoreceptors. Molecular analysis reveals that the mbl locus is large and complex, giving rise to multiple different proteins with common 5′ sequences but different carboxy termini. Mbl proteins are nuclear and share a Cys3His zinc-finger motif which is also found in the TIS11/NUP475/TTP family of proteins and is highly conserved in vertebrates and invertebrates. Functional analysis of mbl, the observation that it also dominantly suppresses the sE-Jun(Asp) gain-of-function phenotype and the phenotypic similarity to mutants in the photoreceptor-specific glass gene suggest that mbl is a general factor required for photoreceptor differentiation.

Bone marrow transplantation reproduces the tristetraprolin-deficiency syndrome in recombination activating gene-2 (-/-) mice. Evidence that monocyte/macrophage progenitors may be responsible for TNFalpha overproduction

Tristetraprolin-deficient [TTP (-/-)] mice exhibit a complex syndrome of myeloid hyperplasia, cachexia, dermatitis, autoimmunity, and erosive arthritis. Virtually the entire syndrome can be prevented by the repeated injection of anti-TNFalpha antibodies (Taylor, G.A., E. Carballo, D.M. Lee, W.S. Lai, M.J. Thompson, D.D. Patel, D.I. Schenkman, G.S. Gilkeson, H.E. Broxmeyer, B.F. Haynes, and P.J. Blackshear. 1996. Immunity. 4:445-454). In the present study, we transplanted bone marrow from TTP (-/-) and (+/+) mice into recombination activating gene-2 (-/-) mice. After a lag period of several months, marrow transplantation from the (-/-) but not the (+/+) mice resulted in the full syndrome associated with TTP deficiency, suggesting that hematopoietic progenitors are responsible for the development of the syndrome. Western blot analysis of supernatants from cultured TTP-deficient macrophages derived from the peritoneal cavity or bone marrow of adult TTP (-/-) mice, or from fetal liver, demonstrated an increased accumulation of TNFalpha after stimulation with LPS compared to control cells, and also increased accumulation of TNFalpha mRNA. This difference was not observed with cultured fibroblasts or T and B lymphocytes. These data suggest that macrophages are among the cells responsible for the effective excess of TNFalpha that leads to the pathology reported in TTP (-/-) animals, and that macrophage progenitors may be involved in the transplantability of this syndrome.

Metal binding properties and secondary structure of the zinc-binding domain of Nup475

Nup475 is a nuclear zinc-binding protein of unknown function that is induced in mammalian cells by growth factor mitogens. Nup475 contains two tandemly repeated sequences YKTELCX8CX5CX3H (Cys3His repeats) that are thought to be zinc-bindin domains. Similar sequences have been found in a number of proteins from various species of eukaryotes. To determine the metal binding properties and secondary structure of the putative zinc-binding domains of Nup475, we have used synthetic or recombinant peptides that contain one or two domain sequences. The peptide with a single domain bound 1.0 +/- 0.1 equivalents of Co2+, and the peptide with two domains bound 1.7 +/- 0.4 equivalents of Co2+. Both peptides bound Co2+ and Zn2+ with affinities similar to those of classical zinc finger peptides. In each case, the Co2+ complex exhibited strong d-d transitions characteristic of tetrahedral coordination. For structural studies by nuclear magnetic resonance spectroscopy, we used a more soluble two-domain peptide that had a single amino acid substitution in a nonconserved amino acid residue in the second Cys3His repeat. The mutant peptide unexpectedly showed loss of one of its metal binding sites and displayed ordered structure for only the first Cys3His sequence. On the basis of the nuclear magnetic resonance data, we propose a structure for the Nup475 metal-binding domain in which the zinc ion is coordinated by the conserved cysteines and histidine, and the conserved YKTEL motif forms a parallel sheet-like structure with the C terminus of this domain. This structure is unlike that of any previously described class of metal binding domain.

Cloning and characterization of two yeast genes encoding members of the CCCH class of zinc finger proteins: zinc finger-mediated impairment of cell growth

Members of the CCCH zinc finger (Zf) protein family have in common two or more repeats of a novel Zf motif consisting of Cys and His residues in the form Cx8Cx5Cx3H [where x is a variable amino acid (aa)]. We used a degenerate polymerase chain reaction (PCR) strategy to clone members of this gene family from Saccharomyces cerevisiae. The deduced aa sequences encoded by these genes, designated CTH1 and CTH2, share 46% overall identity and 59% similarity, largely due to the two highly conserved Zf domains. We found readily detectable expression of a 1.4-kb mRNA encoding Cth1p. The 1.1-kb mRNA encoding Cth2p was barely detectable under normal growth conditions; however, disruption of CTH1 resulted in at least a threefold increase in CTH2 mRNA accumulation. No change in phenotype was detected following disruption of CTH1 and CTH2, either singly or together. In contrast, overexpression of the CTH genes or one of the related mammalian genes, tris-tetraprolin (TTP), caused delayed entry of cell cultures into exponential growth, and a decrease in final cell density. Removal of the Zf domain of Cth1p by truncation or deletion completely reversed this slow growth phenotype, indicating that it was mediated through this highly conserved structural motif.

Chromosomal location of fifteen unique mouse KRAB-containing zinc finger loci

The mammalian genome contains hundreds if not thousands of zinc finger protein (Zfp) genes. While the function of most of these genes remains to be determined, it is clear that a few of them play important roles in gene regulation and development. In studies described here, we have used an interspecific mouse backcross mapping panel to determine the chromosomal location of 15 KRAB-containing zinc finger loci. These loci map to nine different mouse autosomes and the X Chromosome (Chr). Two Chrs, 7 and 9, contain cosegregating pairs of KRAB-containing Zfp genes, indicating that the KRAB-containing Zfp genes have evolved through processes involving regional as well as genome-wide duplication events.

A pathogenetic role for TNF alpha in the syndrome of cachexia, arthritis, and autoimmunity resulting from tristetraprolin (TTP) deficiency

Tristetraprolin (TTP) is a widely expressed potential transcription factor that contains two unusual CCCH zinc fingers and is encoded by the immediate-early response gene, Zfp-36. Mice made deficient in TTP by gene targeting appeared normal at birth, but soon manifested marked medullary and extramedullary myeloid hyperplasia associated with cachexia, erosive arthritis, dermatitis, conjunctivitis, glomerular mesangial thickening, and high titers of anti-DNA and antinuclear antibodies. Myeloid progenitors from these mice showed no increase in sensitivity to growth factors. Treatment of young TTP-deficient mice with antibodies to tumor necrosis factor alpha (TNF alpha) prevented the development of essentially all aspects of the phenotype. These results indicate a role for TTP in regulating TNF alpha synthesis, secretion, turnover, or action. TTP-deficient mice may serve as useful models of the autoimmune inflammatory state resulting from chronic effective TNF alpha excess.

Promoter analysis of Zfp-36, the mitogen-inducible gene encoding the zinc finger protein tristetraprolin

The gene encoding the putative zinc finger protein tristetraprolin (TTP), Zfp-36, is rapidly induced by a variety of mitogens and growth factors. We show here that 77 base pairs 5' of the transcription start site are sufficient for full serum inducibility of the mouse Zfp-36 promoter. This region of the promoter includes consensus sequences for the binding of the transcription factors EGR-1, AP2, and Sp1. In addition, we have identified a previously undescribed element, TTP promoter element 1 (TPE1); this 10-base pair sequence includes a palindrome and is identical in the human, bovine, and mouse genes. Each of the three binding elements, EGR-1, AP2, and TPE1, contribute to the serum induction of Zfp-36 and can confer serum-inducible expression on a heterologous minimal promoter. Gel mobility shift assays demonstrated the formation of complexes consisting of this region of the promoter and cellular nuclear proteins and demonstrated that the extent of complex formation could be altered by treatment of the cells with serum or insulin. These results suggest that the response of Zfp-36 to serum and other mitogens is mediated by a series of cis-acting elements acting in concert to confer full inducible transcription of this gene.

Phosphorylation of tristetraprolin, a potential zinc finger transcription factor, by mitogen stimulation in intact cells and by mitogen-activated protein kinase in vitro

Tristetraprolin (TTP) is a potential transcription factor that contains three PPPPG repeats and two putative CCCH zinc fingers. TTP is encoded by the early response gene Zfp-36, which is highly expressed in response to growth factors and in several hematopoietic cell lines. In the present studies, we investigated the possibility that TTP is phosphorylated in intact cells. In NIH/3T3 cells that were made to overexpress TTP constitutively, we found that the protein was phosphorylated on serine residues, and that this phosphorylation was rapidly (within 10 min) stimulated by several mitogens. In cell-free assays, recombinant mouse TTP was a substrate for the mitogen-activated protein (MAP) kinase. By a combination of protease digestion experiments and site-directed mutagenesis strategies, we found that serine 220 was phosphorylated by p42 MAP kinase in vitro. Expression of mutant TTP in fibroblasts confirmed that serine 220 was one of the major, mitogen-stimulated phosphorylation sites on the protein in intact cells. These results suggest that TTP may be phosphorylated by MAP kinases in vivo and that this phosphorylation may regulate its function.

Zinc inhibits turnover of labile mRNAs in intact cells

For immediate early genes such as the c-fos proto-oncogene, mRNA breakdown is very rapid and is largely responsible for the transient nature of mRNA accumulation after transcription is stimulated. We found that in several types of cultured cells and in mice, Zn++ caused marked accumulation of c-fos mRNA and that of another labile mRNA, that encoding the tristetraprolin (TTP) protein. Exposure of TK-L cells to 100 microM ZnSO4 caused an increase of c-fos and TTP mRNA levels within 1 h that reached peak levels in 4-8 h and remained constant to 12 h. Increases in fos protein accumulation were also noted. When the cells were exposed to Zn++ for 4 h and then exposed to actinomycin D, both c-fos and TTP mRNA levels remained constant for up to 10 h, indicating that Zn++ was preventing the breakdown of both c-fos and TTP mRNA. Also, 100 microM ZnSO4 inhibited protein synthesis in TK-L cells, suggesting that the effect on mRNA accumulation could have been an indirect effect resulting from inhibited protein synthesis. Zn++ was unable to inhibit the breakdown of TTP and c-fos mRNA in vitro; however, extracts from cells exposed to Zn++ were less able to cause the breakdown of TTP and c-fos mRNAs than were extracts from control cells, again suggesting that Zn++ indirectly affects mRNA stability through inhibition of protein synthesis. These studies suggest that in addition to their effects on gene transcription, Zn++ and other divalent cations may regulate gene expression by affecting mRNA stability.

ERF-2, the human homologue of the murine Tis11d early response gene

A human cDNA specifying a member of the Tis11 early response gene family was cloned and sequenced. The human gene differs from its mouse homologue by encoding an additional 97 amino acids at its C-terminal end. The sequence has transactivation-like motifs, an unusual Cys-Ser-Ala-rich motif and displays sequence similarity at the extreme C-terminal end with another Tis11 family member, ERF-1.

A Drosophila melanogaster homolog of the TIS11 family of immediate early genes that can rescue a cdr1 cdc25 mutant strain of fission yeast

A Drosophila melanogaster (Dm) embryonic cDNA library was screened for genes capable of inhibiting wee1+/mik1+ protein kinase (Pk) function. We expected to identify homologs of the Schizosaccharomyces pombe gene nim1+. This gene encodes a Pk capable of phosphorylating and so inhibiting the wee1+ Pk that in turn inhibits p34cdc2. Dm cDNAs capable of complementing the temperature-sensitive phenotype of a nim1/cdr1 cdc25 double mutant strain were identified and found to fall into two classes. One class encodes the Dm Cdc2 protein. The second cDNA class encodes a novel protein containing a central motif consisting of two tandem repeats of a putative Zn(2+)-finger motif. This region is highly conserved in the TIS11 family of immediate early genes, which in mammalian cells are rapidly and transiently induced in response to 12-O-tetradecanoyl phorbol-13-acetate (TPA) and to mitogens such as epidermal growth factor and fibroblast growth factor.

Cloning and characterization of ERF-1, a human member of the Tis11 family of early-response genes

Members of the Tis11 family of early-response genes are characterized by a high degree of sequence similarity around a putative zinc finger motif. They are induced by a variety of cell agonists and polypeptide mitogens, including 12-O-tetradecanoylphorbol-13-acetate (TPA) and epidermal growth factor (EGF). We describe the cloning and sequencing of a human member of this gene family, EGF-response factor 1 (ERF-1), the homolog of the mouse Tis11b/rat cMG1 genes. The human and rodent genes are similar, with 5' UTR, coding sequence, and 3' UTR highly conserved. The promoter/enhancer region and intron sequences contain multiple putative transcription factor binding motifs characteristic of early-response genes. Amino acid sequence comparison of the seven members of the Tis11 family cloned so far identifies a repeated consensus motif of (x+)YKTELC(x+)x5GxCxYGx(x+)CxFxH involving the potential zinc finger. Toward the carboxyterminal end is a region with a high percentage of prolines (15/73) and, partially overlapping, a serine-rich domain (20/54). These may be important as trans-activation and phosphorylation sites. The 3' untranslated region is unusually long, extending over 1,860 bp. The sequence immediately downstream from the translational stop codon has extensive secondary structure potential. The 3' UTR is 60% AT rich, but contains two GC rich (> 70%) regions. In addition there are multiple reiterations of a destabilization sequence, as well as a single UUAUUUAU motif characteristic of mRNAs specifying proteins involved in the inflammatory response. The mRNA contains a consensus polyadenylation signal.

A human putative lymphocyte G0/G1 switch gene homologous to a rodent gene encoding a zinc-binding potential transcription factor

G0S24 is a member of a set of genes (putative G0/G1 switch regulatory genes) that are expressed transiently within 1-2 hr of the addition of lectin or cycloheximide to human blood mononuclear cells. Comparison of a full-length cDNA sequence with the corresponding genomic sequence reveals an open reading frame of 326 amino acids, distributed across two exons. Potential phosphorylation sites include the sequence PSPTSPT, which resembles an RNA polymerase II repeat reported to be a target of the cell cycle control kinase cdc2. Comparison of the derived protein sequence with those of rodent homologs allows classification into three groups. Group 1 contains G0S24 and the rat and mouse TIS11 genes (also known as TTP, Nup475, and Zfp36). Members of this group have three tetraproline repeats. Groups 1 and 2 have a serine-rich region and an "arginine element" (RRLPIF) at the carboxyl terminus. All groups contain cysteine- and histidine-rich putative zinc finger domains and a serine-phenylalanine "SFS" domain similar to part of the large subunit of eukaryotic RNA polymerase II. Comparison of group 1 human and mouse genomic sequences shows high conservation in the 5' flank and exons. A CpG island suggests expression in the germ line. G0S24 has potential sites for transcription factors in the 5' flank and intron; these include a serum response element. Protein and genomic sequences show similarities with those of a variety of proteins involved in transcription, suggesting that the G0S24 product has a similar role.

Chromosomal mapping of the human (MACS) and mouse (Macs) genes encoding the MARCKS protein

The myristoylated, alanine-rich C-kinase substrate, or MARCKS protein, is a major cellular substrate for protein kinase C that is also a high-affinity calmodulin-binding protein. In addition, it is the prototype of a small family of myristoylated, calmodulin-binding protein kinase C substrate proteins. We isolated a phage clone from a mouse genomic library that spanned the entire coding sequence of the mouse MARCKS protein. The first 612 bp of the putative promoter was 89% identical to a corresponding region of the human promoter, and contained at least 59 potential transcription factor binding sites in analogous locations; both human and mouse promoters lacked TATA boxes. The mouse genomic probe was used to localize the mouse gene to chromosome 10, in the middle of a linkage group that corresponds to a region on human chromosome 6q. These data strongly suggested that the human gene would localize to 6q21. This was confirmed by studies of DNA from a patient with del(6)(q21), in which expression of the human gene encoding MARCKS, MACS, was only about 50% of normal; MARCKS mRNA expression in lymphoblast RNA from this patient was only 22% of normal. These studies confirm that the mouse and human MARCKS proteins are products of the same genes in their respective species; differences in their primary sequence can therefore be attributed to species variation rather than to the existence of related genes.