β-Lactone formation in a halogeno-lactonization reaction

Barnett, William E.; McKenna, James C.

doi:10.1039/c29710000551

Cited by 32 publications

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“…It is clear from this experiment that cyclic AMP (as Bt2cAMP) does not detectably influence the elongation rate of the average soluble protein synthesized by these cells. This result is as expected since cyclic AMP has no reproducible influence on the synthesis rate for total soluble protein of H35 cells (1,2,16,21).…”

Section: Resultssupporting

confidence: 72%

“…(iii) The elongation rate for aminotransferase synthesis after The calculation of % aminotransferase sx hesis is based on the stimulation with cyclic AMP is far greater than that for total s104/min (16) and [El soluble protein (up to about 10 amino acids/sec for the enzyme = 100 Ag of total soluble protein/106 cells; hence, k, = 16 X 103 compared to 2 for total soluble protein). If the termination of pg/min.…”

Section: Resultsmentioning

confidence: 99%

“…The minimal deviation rat hepatoma cell line, Reuber H35, first adapted to continuous culture in 1964 (15), has been used for our studies. These cells synthesize various proteins characteristic of normal rat liver (1,(16)(17)(18)(19)(20) and also respond to several hormones that produce responses in rat liver (1-3, 16, 17, 19, 20). Although these cells do not respond to glucagon or isoproterenol (16) because of a lack of receptors,t they do exhibit a strong increase in aminotransferase synthesis in response to cyclic AMP analogs (1,2,16,21,22), insulin (1,16) (5) with 10jg of cycloheximide added per ml of lysis buffer to ensure inhibition of further elongation.…”

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confidence: 99%

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Evidence for acceleration of the rate of elongation of tyrosine aminotransferase nascent chains by dibutyryl cyclic AMP

Roper

Wicks

1978

Proc. Natl. Acad. Sci. U.S.A.

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Analogs of cyclic AMP elevate the synthesis of tyrosine aminotransferase (L-tyrosine:2-oxoglutarate aminotransferase; EC 2.6.1.5) in cultured hepatoma cells and rat liver at a post-transcriptional level but have no discernible effect on total soluble protein synthesis. In order to determine whether cyclic AMP exerts its effect on a step before or after initiation of the synthesis of this enzyme, we have analyzed the ribosomal transit times for both the aminotransferase and total soluble protein in hepatoma cells incubated in the presence or absence of N6,02'-dibutyryl cyclic AMP. The time required for one ribosome to translate one subunit of the "average" soluble protein (transit time) was about 2 min in cells incubated with or without the cyclic AMP analog. In contrast, the transit time for tyrosine aminotransferase was found to be reduced from [5][6][7][8] min under basal conditions to as low as 45 sec after exposure to dibutyryl cyclic AMP. Although the degree of effect varied from experiment to experiment, the relative rate of aminotransferase nascent chain elongation was found to be proportional to the stimulation of its activity. In contrast, dexamethasone did not alter the rate of aminotransferase elongation even though it elevated enzyme activity between 5-and 10-fold. These data are consistent with the hypothesis that induction of tyrosine aminotransferase with cyclic AMP analogs occurs by stimulation of the rate at which ribosomes translate pre-existing mRNA in contrast to adrenal steroids which act by increasing the level of translatable mRNA coding for this enzyme.

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Section: Resultssupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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Evidence for acceleration of the rate of elongation of tyrosine aminotransferase nascent chains by dibutyryl cyclic AMP

Roper

Wicks

1978

Proc. Natl. Acad. Sci. U.S.A.

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“…This is interesting because the genes encoding TAT and PEPCK share other forms of gene control. For example, transcription of both genes is inducible by glucocorticosteroids and by cAMP (36,37), although insulin has opposite effects on gene activity. Furthermore, the developmental expression of Tat-i and Pck-J is similar, with gene activity being induced shortly after birth.…”

Section: Discussionmentioning

confidence: 99%

Coordinate regulation of two genes encoding gluconeogenic enzymes by the trans-dominant locus Tse-1.

Lem

Chin

Thayer

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

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Tissue-specific extinguisher-i (Tse-1) is a mouse genetic locus that can repress liver-specific tyrosine aminotransferase gene expression in trans. To search for other Tse-l-responsive genes, hepatoma microcell hybrids retaining mouse chromosome 11 or human chromosome 17, containing murine Tse-1 and human TSEI, respectively, were screened for expression of liver-specific mRNAs. While most liver gene activity was unaffected in such hybrids, phosphoenolpyruvate carboxykinase and tyrosine aminotransferase gene expression was coordinately repressed in these clones. Extinction of both genes was apparently mediated by a single genetic locus that resides on human chromosome 17.Cellular differentiation is generally viewed as an orchestrated process in which specific gene sets are activated or repressed at defined developmental times. These events culminate in the establishment of lineage-dependent patterns of transcription that are the basis of cell specialization. The molecular mechanisms that control these processes are poorly understood.Tissue-specific genes are primarily regulated at the level of transcription (1, 2), and discrete sequence elements are required in cis for proper developmental control (3). These observations support the widely-held view that trans-acting factors play key roles in regulating eukaryotic gene activity. Further analysis of this mechanism of gene control will require the characterization of specific regulatory factors in both genetic and biochemical terms.The first clear evidence for trans-regulation of differentiated functions in mammalian cells was reported by Davidson et al. in 1966 (4). They observed that melanoma-fibroblast hybrid cells failed to produce the melanin pigment characteristic of their differentiated melanoma parent. This "extinction" phenomenon proved to be both general and bidirectional: most stable hybrids formed by fusing distinctly different cell types fail to express the tissue-specific products of either parent (5, 6). However, extinguished traits can be reexpressed in hybrid segregants that have eliminated chromosomes of one of the parental cells (7-9). In reexpressing segregants, heterologous gene activation may be observed (10, 11). Thus, expression of tissue-specific genes can be manipulated experimentally in intertypic hybrids, and this provides a system with the potential to define genetic factors that regulate gene activity in trans.Liver-specific gene expression in intertypic hepatoma hybrids has been studied for many years, and, thanks largely to the work of Weiss and coworkers (7-11), this remains the most comprehensively analyzed hybrid cell system to date. Two important facts about tissue-specific gene expression in this system have recently been established. First, virtually all liver-specific gene activity is repressed in genotypically complete rat hepatoma-mouse fibroblast hybrids, but reexpression occurs upon loss of relatively few fibroblast chromosomes (12). Second, extinction of particular liver genes is mediated by discrete genetic loci...

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“…We have determined the influence of Bt2cAMP on several translational events during the tyrosine aminotransferase synthesis with the following results. (1) The number of nascent tyrosine aminotransferase chains increased, whereas no effect was measured on the number of nascent total protein chains. (2) The rate of elongation along the tyrosine aminotransferase mRNA and total mRNA is not enhanced by BtzcAMP.…”

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Studies on the Posttranscriptional Site of cAMP Action in the Regulation of the Synthesis of Tyrosine Aminotransferase

Snoek¹,

Poll²,

Voorma³

et al. 1981

European Journal of Biochemistry

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Synthesis of L-tyrosine : 2-oxoglutarate aminotransferase (EC 2.6.1.5) can be induced by N6, in Reuber H35 cell cultures. Actinomycin D fails to block this induction which indicates a target for BtzcAMP at a posttranscriptional level. We have determined the influence of Bt2cAMP on several translational events during the tyrosine aminotransferase synthesis with the following results.(1) The number of nascent tyrosine aminotransferase chains increased, whereas no effect was measured on the number of nascent total protein chains. (2) The rate of elongation along the tyrosine aminotransferase mRNA and total mRNA is not enhanced by BtzcAMP. (3) The induced synthesis of tyrosine aminotransferase is more sensitive to the inhibition of elongation. We conclude from our results that BtzcAMP induces the synthesis of tyrosine aminotransferase by an increase in the rate of initiation on the tyrosine aminotransferase mRNA.Derivatives of CAMP increase the rate of synthesis of L-tyrosine : 2-oxoglutarate aminotransferase (tyrosine aminotransferase) in Reuber H35 hepatoma cells [l, 21. This increase may be due to (a) a relative increase in the amount of polysoma1 tyrosine aminotransferase mRNA, (b) a relative increase of the elongation rate on the tyrosine aminotransferase mRNA, or (c) an increase in the number of ribosomes translating the same amount of tyrosine aminotransferase mRNA at an unchanged elongation rate.The molecular events in the induction of tyrosine aminotransferase synthesis by N6,02'-dibutyryl-adenosine 3',5'-monophosphate (BtzcAMP) are still poorly understood. Actinomycin D or cordycepin (3'-deoxyadenosine) block the induction of tyrosine aminotransferase synthesis by corticosteroids in liver and hepatoma cell lines [3,4]; they also block the induction of tyrosine aminotransferase synthesis by BtzcAMP in some liver systems [5] but fail to block the induction by Bt2cAMP in other liver systems and hepatoma cells [6-lo]. This indicates that no single mechanism exists for cAMP regulation; it also indicates that there is at least one target at a posttranscriptional level. To investigate the three possibilities (a, b and c) further, we determined the number of growing tyrosine aminotransferase polypeptide chains with pactamycin applied as inhibitor of the initiation of polypeptide synthesis [l 11. The radioactivity recovered in tyrosine aminotransferase molecules after the simultaneous addition of pactamycin and labeled amino acids reflects one half of the number of nascent tyrosine aminotransferase enzyme molecules. Moreover, ribosomal transit times were measured to check whether the rate of elongation on tyrosine aminotransferase mRNA and total mRNA is affected by Bt2cAMP [12-141. Under the conditions used in this study, we found that induction of tyrosine aminotransferase synthesis by BtzcAMP is due to an increase in the specific initiation of the mRNA for tyrosine aminotransferase. Several reports have suggested that the rate of protein synthesis is regulated by the rate of initiation of mRNA translation [13,15...

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β-Lactone formation in a halogeno-lactonization reaction

Cited by 32 publications

References 0 publications

Evidence for acceleration of the rate of elongation of tyrosine aminotransferase nascent chains by dibutyryl cyclic AMP

Evidence for acceleration of the rate of elongation of tyrosine aminotransferase nascent chains by dibutyryl cyclic AMP

Coordinate regulation of two genes encoding gluconeogenic enzymes by the trans-dominant locus Tse-1.

Studies on the Posttranscriptional Site of cAMP Action in the Regulation of the Synthesis of Tyrosine Aminotransferase

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