Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The primary structure of rat tyrosine aminotransferase (L-tyrosine:2-oxoglutarate aminotransferase; EC 2.6.1.5), a liver-specific enzyme involved in gluconeogenesis, has been deduced from the nucleotide sequence of a cloned full-length cDNA. The mRNA is 2362 nucleotides long (excluding the poly(A) tail) and codes for a polypeptide of 454 amino acids with a molecular weight of 50634. Unambiguous identification was obtained by comparison of this sequence with the amino acid sequences of several peptides obtained from the purified enzyme.
J Mol Biol 1985 Jul 20
PMID:Complete complementary DNA of rat tyrosine aminotransferase messenger RNA. Deduction of the primary structure of the enzyme. 286 82

The structural gene encoding liver-specific tyrosine aminotransferase (TAT; EC 2.6.1.5) was assigned to mouse chromosome 8 by screening a series of hybrid cell lines for retention of murine Tat-1 gene sequences by genomic Southern blotting. This assignment demonstrated that the Tat-1 structural gene was not syntenic with Tse-1, a chromosome 11-linked locus that negatively regulates TAT expression in trans (A. M. Killary and R. E. K. Fournier, Cell 38:523-534, 1984). We also showed that the fibroblast Tat-1 gene was systematically activated in hepatoma X fibroblast hybrids retaining fibroblast chromosomes 8 in the absence of chromosome 11 but was extinguished in cells retaining both fibroblast chromosomes. Thus, the TAT structural genes of both parental cell types were coordinately regulated in the intertypic hybrids, and the TAT phenotype of the cells was determined by the presence or absence of fibroblast Tse-1.
Mol Cell Biol 1985 Sep
PMID:Chromosomal assignment and trans regulation of the tyrosine aminotransferase structural gene in hepatoma hybrid cells. 287 83

Tyrosine aminotransferase (TAT, EC 2.6.1.5) from the kinetoplastid, Crithidia fasciculata, was purified over 2000 fold to electrophoretic homogeneity. The native form of the enzyme had a molecular weight of approximately 100,000, whereas under denaturing conditions it produced two polypeptides of approximately 50,000 and 48,000, respectively. Absence of a reaction with the periodic acid-Schiff stain suggested that the crithidial enzyme was not a glycoprotein. It was relatively stable and remained active over a wide range of pH and temperature. It exhibited a broad substrate specificity and was able to utilize L-tyrosine, L-tryptophan, and L-phenylalanine as amino donors. Antiserum produced against partially purified crithidial tyrosine aminotransferase failed to inhibit the enzymatic activity. The same antiserum cross-reacted with a soluble extract from Trypanosoma brucei gambiense, but not with that from normal mouse liver, confirming evolutionary conservatism between the two protozoa.
Mol Biochem Parasitol 1987 Aug
PMID:Purification and characterization of a tyrosine aminotransferase from Crithidia fasciculata. 289 Jan 1

Kinetics of tyrosine aminotransferase (TAT) mRNA synthesis in Morris rat hepatoma cell lines 7777 and 8994 after dexamethasone treatment (10(-7) M) was studied by molecular hybridization of the RNA with cloned fragments of TAT gene from rat liver cells. It was demonstrated that initiation of TAT gene transcription increased 20 minutes after glucocorticoid treatment. The level of TAT mRNA was not induced by dexamethasone in rat hepatoma cell line 8994. Actinomycin D prevented the deinduction of TAT by stabilization of TAT mRNA.
Mol Biol (Mosk)
PMID:[Regulation of the transcription of the tyrosine aminotransferase gene by glucocorticoids in Morris hepatoma 7777 and 8994 cells]. 289 90

The two independently derived hepatoma cell lines (HTC and Fu5-5) have previously been shown to display different sensitivities for the induction of tyrosine aminotransferase (TAT) enzyme activity and mRNA levels by glucocorticoids with the enzyme being half-maximally induced at approximately 7-fold higher concentrations of dexamethasone in HTC cells than in Fu5-5 cells. In the present study we investigated the induction of TAT activity by cAMP in order to see whether the difference is limited to the steroidal induction. Using the stable cAMP derivative (8-(4-chlorophenylthio)-cAMP) as an inducer, we found that a 6-fold higher cAMP concentration was needed in HTC cells to achieve the same extent of enzyme induction as in Fu5-5 cells. The induction of TAT enzyme activity could be accounted for by an increased amount of TAT mRNA. Further experiments involving sequential addition of both inducers in general showed a synergism of steroids and cAMP for TAT induction in HTC cells only at submaximal concentrations of steroid; in Fu5-5 cells, the occurrence of synergism depended on the order of addition of inducers. The maximal response in HTC cells was limited to the value that could be achieved by induction with steroid alone. In Fu5-5 cells, however, the steroid response could be augmented when cAMP was added to cells already maximally induced by steroid. This demonstrates that the effect of a combination of cAMP and steroids depends on their concentration, the sequence of their addition, and the rat hepatoma cell line used. Collectively the data suggest that a common pretranslational event determines the differential sensitivity of TAT induction by glucocorticoids and by cAMP in HTC and Fu5-5 cells. Furthermore a second, or possibly the same, common event also regulates the maximum level of TAT induction that is obtainable under most conditions with glucocorticoids and/or cAMP.
Mol Endocrinol 1987 Jan
PMID:Differential sensitivity of HTC and Fu5-5 cells for induction of tyrosine aminotransferase by 3',5'-cyclic adenosine monophosphate. 290 Oct 31

The glucocorticoid-progesterone responsive element (GRE/PRE) of the tyrosine aminotransferase (TAT) gene is a steroid-inducible enhancer. We show that the GRE/PRE can also work in the absence of a distal promoter element when located 5' to the ovalbumin TATA box. The GRE/PRE in this position retains progesterone or glucocorticoid receptor and hormone dependency for the induction of gene expression. Initiation of transcription occurs correctly, and induction occurs at the mRNA level. These data indicate that a steroid-inducible enhancer can function without a distal promoter element.
Mol Endocrinol 1988 Dec
PMID:A steroid response element can function in the absence of a distal promoter. 290 64

The enzyme tyrosine aminotransferase (TAT) is induced by unusually low concentrations of glucocorticoids in Fu5-5 cells. We have isolated clones of Fu5-5 cells infected with mouse mammary tumor virus (MMTV) in order to simultaneously compare the glucocorticoid regulation of the host cell gene, TAT, with that of another primary inducible gene, MMTV. In the two clones that were examined in detail, MMTV RNA induction occurred at 4- to 11-fold higher concentrations of dexamethasone than those needed for induction of TAT mRNA. Furthermore, the amount of agonist activity displayed by the irreversible antiglucocorticoid dexamethasone 21-mesylate was greater for the induction of TAT mRNA than for MMTV RNA. These results extend our previous observations of unequal sensitivity of induction of TAT enzyme activity in two hepatoma cell lines and show that differential glucocorticoid regulation of gene induction within the same cell can occur at a pretranslational step. The present data also indicate that the unusual properties of TAT gene induction are not shared by all primary, glucocorticoid-inducible responses of the same cell and imply that additional factors mediating differential regulation of glucocorticoid-responsive genes are involved.
Mol Endocrinol 1988 Nov
PMID:Unlinked regulation of the sensitivity of primary glucocorticoid-inducible responses in mouse mammary tumor virus infected Fu5-5 rat hepatoma cells. 290 13

1. The response of tyrosine aminotransferase activity in isolated liver cells has been studied under several conditions. 2. Activity is increased over a 5 h period by both glucagon and glucocorticoids in cells from adrenalectomized rats. The results do not support the view that glucagon action is dependent on preexposure of cells to steroid. 3. In cells from fed animals, significant stimulation is seen only when both glucagon and steroid are present together. 4. In cells from 48 h fasted rats steroid is effective, but glucagon is not significant so. 5. These anomalies are attributed to the differences in hormonal and nutritional status between the animals from which the cells are isolated.
Mol Cell Biochem 1981 Jan 20
PMID:Factors affecting induction of tyrosine aminotransferase in isolated rat liver cells. 611 64

The induction of tyrosine aminotransferase by a variety of steroids was studied in cells from a hepatoma tissue culture (HTC). We have defined a class of steroids that induce TAT synthesis to a higher level than optimal inducers described earlier; these are called supra-inducers. When TAT induction is compared with the binding of the steroids to the cytoplasmic receptor or to their binding in the whole cell, a good correlation between binding in vivo of the hormone and its induction capacity can be established, whereas such a correlation was not systematically observed in vitro. A very short exposure of HTC cells to either dexamethasone or corticosterone is sufficient to induce TAT. When the inducer is removed from the culture medium a few minutes after its administration, the intracellular hormone concentration decreases very rapidly but TAT will be synthesized at its maximal rate. Thus the hormones behave as a starting signal for the optimal synthesis of the enzyme, and their presence in the culture medium is not necessary throughout the entire induction period.
Mol Cell Endocrinol 1981 May
PMID:Relations between steroid-cell contact, steroid-binding and induction of tyrosine aminotransferase. 611 76

Rat parenchymal hepatocytes isolated with collagenase were cultured as monolayers in Williams medium E supplemented with calf serum. Freshly isolated cells showed very low activities of various liver functions, and they had to be cultured for 6-24 h to allow recovery of these functions. Insulin and dexamethasone greatly increased cell viability in primary. After culture for 24 h, these cells showed various liver functions as seen in vivo and responded well to various added hormones and amino acids. The concentrations of amino acids in the medium regulated synthesis of serum proteins and insulin stimulated lipogenesis, which in turn regulated synthesis of lipoproteins. Insulin also stimulated glycogen synthesis and the stimulation was parallel with the number of insulin receptors. Glucagon stimulated glycogenolysis and its stimulation involved the function of the cytoskeleton. Glucagon and dexamethasone induced various enzymes of amino acid catabolism, such as tryptophan oxygenase, tyrosine aminotransferase and serine dehydratase. These inductions were inhibited by insulin or catecholamine. The effect of catecholamine was due to its alpha-adrenergic action. The beta-action of isoproterenol was low in freshly isolated cells, but increased during culture of the cells. Acquirement of hormonal responses during neonatal development can be studied in this culture system. Mature hepatocytes in culture are usually quiescent, but when insulin and epidermal growth factor were added, DNA synthesis by the cells increased markedly and they showed density-dependent growth. In this culture system, serum could be omitted for 2 days when the dishes were coated with fibronectin without appreciable change of functions, but serum was needed for longer culture of the cells. A factor that increased cell survival was found in serum and in pituitary gland. These results show that hepatocytes in primary culture are a simple and useful system for studies of liver functions in vitro and related works were also reviewed.
Mol Cell Biochem 1982 Apr 02
PMID:Use of hepatocytes in primary culture for biochemical studies on liver functions. 612 41


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