Lunardi, Joël and Attardi, Giuseppe (1991) Differential regulation of expression of the multiple ADP/ATP translocase genes in human cells. Journal of Biological Chemistry, 266 (25). pp. 16534-16540. ISSN 0021-9258. http://resolver.caltech.edu/CaltechAUTHORS:LUNjbc91
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The expression of the genes encoding the three isoforms of the human ADP/ATP translocase (T1, T2, and T3) has been investigated in cultured cell systems under different experimental conditions, using isoform- specific probes. In several human cell lines tested, i.e. HeLa, Hep3B, 143B, HL60, the T3 gene is expressed as a single 1300-nucleotide mRNA, whereas the T2 gene produces two species of mRNA, 1450 and 1600 nucleotides in size. These two species, which are present in HeLa cells in approximately equivalent amounts, were shown to derive from the use of two different polyadenylation signals. The gene for the muscle-specific isoform of ADP/ATP translocase, T1, was not found to be expressed in any of the cell lines investigated. The levels of T2 and T3 mRNAs in HeLa cells are differentially affected by the growth conditions. In fact, the T2 mRNA level remains relatively constant throughout the exponential and stationary phases, whereas the T3 mRNA level decreases progressively in the second half of the exponential phase and in the stationary phase down to less than 50%. This difference in quantitative behavior of the two mRNAs must reflect changes in their rates of synthesis, since their half-lives are very similar (t^1/2 = 5-6 h), with no significant growth-related differences. Treatment of HL60 cells with 12-O-tetradecanoylphorbol-13-acetate or retinoic acid, two agents which induce cessation of cell proliferation and cell differentiation, resulted in a marked decrease in both T2 and T3 mRNA levels. Exposure of HeLa cells to chloramphenicol produced a pronounced decrease in the levels of both T2 and T3 mRNAs after 48 to 72 h of treatment. Half-life time measurements strongly suggested that this decrease reflected a reduction in the rate of synthesis of the two transcripts. Treatment of HeLa cells with dinitrophenol also produced a dramatic decrease in the steady state levels of both T2 and T3 mRNA, which, however, in contrast to the just mentioned situation, could be accounted for by a decrease in their metabolic stability. Control experiments indicated that the chloramphenicol- and dinitrophenol-induced changes were not a nonspecific consequence of mitochondrial dysfunction. The observations reported here clearly demonstrate that the expression of the multiple ADP/ATP translocase genes in human cells is sensitive to the cell physiological conditions, responding to the varying cellular demands by changes in the rate of synthesis or stability of their mRNAs.
|Additional Information:||Copyright © 1991 by the American Society for Biochemistry and Molecular Biology. (Received for publication, February 19, 1991) We thank Dr. P. Jeanteur (Université des Sciences et Techniques du Languedoc, Montpellier, France) for the gift of the GPDHase clone. The technical assistance of Arger Drew and Lisa Tefo is gratefully acknowledged. These investigations were supported by National Institutes of Health Grant GM-11726 (to G.A.) and an Eleanore Roosevelt-International Union against Cancer Fellowship (to J.L.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “aduertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.|
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|Deposited On:||11 Sep 2007|
|Last Modified:||26 Dec 2012 09:41|
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