Induction of tumor promotor-inducible genes in murine 3T3 cell lines and tetradecanoyl phorbol acetate-nonproliferative 3T3 variants can occur through protein kinase C-dependent and -independent pathways.

We isolated a group of genes that are rapidly and transiently induced in 3T3 cells by tetradecanoyl phorbol acetate (TPA). These genes are called TIS genes (for TPA-inducible sequences). Epidermal growth factor (EGF), fibroblast growth factor (FGF), and TPA activated TIS gene expression with similar induction kinetics. TPA pretreatment to deplete protein kinase C activity did not abolish the subsequent induction of TIS gene expression by epidermal growth factor or fibroblast growth factor; both peptide mitogens can activate TIS genes through a protein kinase C-independent pathway(s). We also analyzed TIS gene expression in three TPA-nonproliferative variants (3T3-TNR2, 3T3-TNR9, and A31T6E12A). The results indicate that (i) modulation of a TPA-responsive sodium-potassium-chloride transport system is not necessary for TIS gene induction either by TPA or by other mitogens and (ii) TIS gene induction is not sufficient to guarantee a proliferative response to mitogenic stimulation.     

“Macrophage” nitric oxide synthase is a glucocorticoid-inhibitable primary response gene in 3T3 cells

Both nitric oxide and prostaglandins are potent paracrine mediators of intercellular communication. An endotoxin-lipopolysaccharide (LPS) inducible form of nitric oxide synthase (mac-NOS) has recently been cloned from murine macrophages. An inducible prostaglandin synthase (TIS1O/PGS-2), cloned from 3T3 cells, is also induced in LPS-activated macrophage. Because of the wide range of ligands that induce primary response genes in 3T3 cells, the ease of studying chimeric promoter constructs in 3T3 cells, and the importance of both nitric oxide and prostaglandins as paracrine mediators, we examined expression of mac-NOS in 3T3 cells. Tetradecanoyl phorbol-13 acetate (TPA), forskolin, platelet-derived growth factor, fibroblast growth factor, and serum all induce mac-NOS expression in Swiss 3T3 cells. Thus the mac-NOS gene can respond to a far wider range of inducers than previously suspected. mac-NOS is a primary response gene; cycloheximide does not block induction. TPA-induced mac-NOS and TIS10/PGS-2 mRNA accumulation patterns are similar. LPS is a potent inducer of mac-NOS in Swiss 3T3 cells but cannot induce TIS10/PGS-2. In contrast, v-src expression induces TIS10/PGS-2 message, but not iNOS message in a BALB/c 3T3 cell line containing a temperature-sensitive v-src gene. Dexamethasone (DEX) prevents induction of TIS10/PGS-2, but not most other primary response genes. DEX also blocks mac-NOS induction in Swiss 3T3 cells. The inducible TIS10/PGS-2 and mac-NOS genes, responsible for the production of two distinct paracrine agents, appear to share many regulatory features in 3T3 cells. © 1993 Wiley-Liss, Inc.     

Dexamethasone inhibits mitogen induction of the TIS10 prostaglandin synthase/cyclooxygenase gene.

Glucocorticoids block the induced secretion of prostaglandins in a variety of biological contexts. We have identified a primary response gene, TIS10, which encodes a mitogen-inducible prostaglandin synthase/cyclooxygenase in Swiss 3T3 cells. TIS10 is distinct from prostaglandin synthase/cyclooxygenase. (EC 1.14.99.1), previously cloned from mouse, man, and sheep. Dexamethasone blocks prostaglandin E2 synthesis by 3T3 cells in response to tetradecanoylphorbol acetate. Dexamethasone also blocks both phorbol ester- and forskolin-induced TIS10 mRNA accumulation. In contrast, phorbol esters, forskolin, and dexamethasone have little or no effect on the levels of prostaglandin synthase/cyclooxygenase mRNA in 3T3 cells. Moreover, dexamethasone does not inhibit induction of TIS8/egr-1, another primary response gene. Inhibition of the synthesis of TIS10 prostaglandin synthase/cyclooxygenase may be a principal mechanism by which glucocorticoids block prostaglandin synthesis and secretion.     

Synthesis,degradation, and subcellular localization of proteins encoded by the primary response genes TIS7/PC4 and TIS21/PC3

Murine TIS7 and TIS21 cDNAs were cloned from phorbol ester-induced Swiss 3T3 cells. The cognate rat cDNAs. PC4 and PC3, were cloned from nerve growth factor (NGF)-treated PC12 pheochromocytoma cells. The TIS7/PC4 and TIS21/PC3 primary response genes are rapidly and transiently induced in response to serum, phorbol esters, and polypeptide growth factors in quiescent Swiss 3T3 cells and by NGF and other ligands in PC12 cells. In both 3T3 and PC12 cells the appearance of the TIS21/PC3 message precedes that of TIS7/PC4 message following ligand stimulation, suggesting that the TIS21/PC3 protein is likely to be synthesized more rapidly than the TIS7/PC4 protein. Using antisera prepared against recombinant TIS21 and TIS7 proteins, we find that the TIS21/PC3 protein is, indeed, synthesized more rapidly than the TIS7/PC4 protein following stimulation in both 3T3 and PC12 cells. In addition, “pulse-chase” experiments demonstrate that the TIS21/PC3 protein is degraded much more rapidly than the TIS7/PC4 protein. The sequences of the predicted PC3 and PC4 proteins have lead to the speculation that these two proteins may both be secreted from cells following stimulation. The PC4 protein is reported to have some sequence similarity to interferons. The TIS21/PC3 protein contains a presumptive leader sequence. Using our antisera to the recombinant proteins, however, we cannot detect secretion of radiolabelled TIS7/PC4 or TIS21/PC3 protein. Immunohistochemical and subcellular fractionation experiments suggest that the TIS7 protein is a membrane associated, non-nuclear intracellular protein. The TIS21 protein, in contrast, is' a non-nuclear, soluble intracellular protein. © 1994 Wiley-Liss, Inc.     

Cholera toxin induces expression of the immediate-early response gene JE via a cyclic AMP-independent signaling pathway.

Cholera toxin (CT) activates expression of two immediate-early response genes (JE and TIS10) in quiescent BALB/c 3T3 cells. Increases in cyclic AMP (cAMP) levels in response to CT are likely responsible for the induction of TIS10 gene expression, since treatment with 8-Br-cAMP and increasing the intracellular levels of cAMP by treatment with forskolin induce TIS10 gene expression. In contrast, neither forskolin nor 8-Br-cAMP induces JE gene expression. 3-Isobutyl-1-methylxanthine, which stabilizes intracellular cAMP, potentiates CT-induced TIS10 gene expression but has no effect on CT-induced JE gene expression. Thus, induction of JE by CT is independent of the cAMP produced in response to CT. Induction of JE by CT does not require protein kinase C (PKC), since depleting cells of PKC activity has no effect on the induction of JE by CT. CT-induced expression of JE can be distinguished from CT-induced TIS10 gene expression by using protein kinase inhibitors and inhibitors of arachidonic acid metabolism, further suggesting distinct signaling pathways for CT-induced JE and TIS10 gene expression. Thus, induction of JE gene expression by CT results from the activation of an intracellular signaling pathway that is independent of cAMP production. This pathway is independent of PKC activity and uniquely sensitive to inhibitors of protein kinases and arachidonic acid metabolism.     

The anti-proliferative gene TIS21 is involved in osteoclast differentiation

The remodeling process of bone is accompanied by complex changes in the expression levels of various genes. Several approaches have been employed to detect differentially-expressed genes in regard to osteoclast differentiation. In order to identify the genes that are involved in osteoclast differentiation, we used a cDNAarray-nylon membrane. Among 1,200 genes that showed a measurable signal, 19 genes were chosen for further study. Eleven genes were up-regulated; eight genes were downregulated. TIS21 was one of the up-regulated genes which were highly expressed in mature osteoclasts. To verify the cDNA microarray results, we carried out RT-PCR and real-time RT-PCR for the TIS21 gene. The TIS21 mRNA level was higher in differentiated-osteoclasts when compared to undifferentiated bone-marrow macrophages. Furthermore, the treatment with 1 mM of a TIS21 antisense oligonucleotide reduced the formation of osteoclasts from the bone-marrow-precursor cells by approximately 30%. These results provide evidence for the potential role of TIS21 in the differentiation of osteoclasts     

Accuracy improvement for identifying translation initiation sites in microbial genomes

MOTIVATION: At present the computational gene identification methods in microbial genomes have a high prediction accuracy of verified translation termination site (3' end), but a much lower accuracy of the translation initiation site (TIS, 5' end). The latter is important to the analysis and the understanding of the putative protein of a gene and the regulatory machinery of the translation. Improving the accuracy of prediction of TIS is one of the remaining open problems. RESULTS: In this paper, we develop a four-component statistical model to describe the TIS of prokaryotic genes. The model incorporates several features with biological meanings, including the correlation between translation termination site and TIS of genes, the sequence content around the start codon; the sequence content of the consensus signal related to ribosomal binding sites (RBSs), and the correlation between TIS and the upstream consensus signal. An entirely non-supervised training system is constructed, which takes as input a set of annotated coding open reading frames (ORFs) by any gene finder, and gives as output a set of organism-specific parameters (without any prior knowledge or empirical constants and formulas). The novel algorithm is tested on a set of reliable datasets of genes from Escherichia coli and Bacillus subtillis. MED-Start may correctly predict 95.4% of the start sites of 195 experimentally confirmed E.coli genes, 96.6% of 58 reliable B.subtillis genes. Moreover, the test results indicate that the algorithm gives higher accuracy for more reliable datasets, and is robust to the variation of gene length. MED-Start may be used as a postprocessor for a gene finder. After processing by our program, the improvement of gene start prediction of gene finder system is remarkable, e.g. the accuracy of TIS predicted by MED 1.0 increases from 61.7 to 91.5% for 854 E.coli verified genes, while that by GLIMMER 2.02 increases from 63.2 to 92.0% for the same dataset. These results show that our algorithm is one of the most accurate methods to identify TIS of prokaryotic genomes. AVAILABILITY: The program MED-Start can be accessed through the website of CTB at Peking University: http://ctb.pku.edu.cn/main/SheGroup/MED_Start.htm.     

Effects of strigolactone-biosynthesis inhibitor TIS108 on Arabidopsis

TIS108 is a triazole-type strigolactone (SL)-biosynthesis inhibitor that reduces the level of 2′-epi-5-deoxystrigol (epi-5DS) in rice. Here we report the effects of TIS108 on Arabidopsis. Treatment of TIS108 increased the number of branches and repressed root hair elongation as was observed in SL-deficient mutants, and co-application of GR24, a synthetic SL analog, recovered the TIS108-induced phenotype to that of wild-type. In addition, MAX3 and MAX4 genes in the SL-biosynthesis pathway were upregulated in TIS108-treated Arabidopsis, probably due to feedback regulation caused by SL deficiency. These results indicate that TIS108 is an effective tool for regulating SL production in Arabidopsis.     

TIS11D is a Candidate Pro-Apoptotic p53 Target Gene

A number of target genes for the tumor suppressor, p53, have been identified, however, the mechanisms that contribute to p53-dependent apoptosis remain to be fully elucidated. In a comprehensive screen for p53 target genes by differential display, we have identified TIS11D as a p53-inducible gene. Induction of TIS11D mRNA was confirmed by Northern Blot in response to p53 expression. Inducible expression of TIS11D resulted in inhibition of cell proliferation and apoptosis. These data suggest TIS11D as a candidate p53 target gene that may be part of the network of genes responsible for p53-dependent apoptosis.