A problem of major interest in current biology centers not only on the question of the mechanisms whereby hormones regulate the expression of specific genes, but also on how coordinate expression of genes -- e.g., for individual enzymes within a metabolic pathway -- is achieved. Expression of the genes encoding enzymes of the urea cycle constitutes an excellent model for investigating both aspects of this problem. The urea cycle is comprised of 2 mitochondrial and 3 cytosolic enzymes, all encoded by nuclear genes which are coordinately expressed to a significant extent only in liver of ureotelic animals. Levels of the urea cycle enzymes in mammals are responsive to changes in dietary protein content, glucocorticoids, glucagon, insulin, and thyroid hormone. Results from this laboratory, as well as from others, have demonstrated that a primary component of these changes involves altered cellular concentrations of the mRNAs for these enzymes. Studies in this laboratory have also demonstrated that the transcription rate of these genes in rat liver is increased in response to cyclic AMP and that glucocorticoids and dibutyryl cyclic AMP are each necessary and sufficient to elevate mRNA levels for urea cycle enzymes in rat hepatocytes cultured in serum-free medium. This grant proposes to isolate and characterize genomic DNA clones encoding two of the urea cycle enzymes -- carbamyl phosphate synthetase I and argininosuccinate synthetase. mRNAs for these two enzymes exhibit distinctive patterns of expression in cultured rat hepatocytes. Recombinant DNA constructs incorporating genomic DNA sequences for these enzymes and a reporter gene will be used in cell transfection experiments to identify and characterize cis-acting DNA sequences involved in the response to hormones. Preliminary experiments will also be undertaken to identify DNA-binding proteins with sequence- specific affinity for regions of DNA shown by transfection experiments to be important for expression.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK033144-07
Application #
3231505
Study Section
Biochemistry Study Section (BIO)
Project Start
1983-12-01
Project End
1991-11-30
Budget Start
1989-12-01
Budget End
1990-11-30
Support Year
7
Fiscal Year
1990
Total Cost
Indirect Cost
Name
University of Pittsburgh
Department
Type
Schools of Medicine
DUNS #
053785812
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Nussler, A K; Liu, Z Z; Hatakeyama, K et al. (1996) A cohort of supporting metabolic enzymes is coinduced with nitric oxide synthase in human tumor cell lines. Cancer Lett 103:79-84
Kelly, E; Morris Jr, S M; Billiar, T R (1995) Nitric oxide, sepsis, and arginine metabolism. JPEN J Parenter Enteral Nutr 19:234-8
Morris Jr, S M; Billiar, T R (1994) New insights into the regulation of inducible nitric oxide synthesis. Am J Physiol 266:E829-39
Chicco, A G; Adibi, S A; Liu, W Q et al. (1994) Regulation of gene expression of branched-chain keto acid dehydrogenase complex in primary cultured hepatocytes by dexamethasone and a cAMP analog. J Biol Chem 269:19427-34
Nussler, A K; Billiar, T R; Liu, Z Z et al. (1994) Coinduction of nitric oxide synthase and argininosuccinate synthetase in a murine macrophage cell line. Implications for regulation of nitric oxide production. J Biol Chem 269:1257-61
Morris Jr, S M (1992) Regulation of enzymes of urea and arginine synthesis. Annu Rev Nutr 12:81-101
Morris Jr, S M; Kepka-Lenhart, D; McGill, R L et al. (1992) Specific disruption of renal function and gene transcription by cyclosporin A. J Biol Chem 267:13768-71
Morris Jr, S M; Kepka-Lenhart, D; Curthoys, N P et al. (1991) Disruption of renal function and gene expression by FK 506 and cyclosporine. Transplant Proc 23:3116-8
Curran, R D; Ferrari, F K; Kispert, P H et al. (1991) Nitric oxide and nitric oxide-generating compounds inhibit hepatocyte protein synthesis. FASEB J 5:2085-92
Morris Jr, S M; Sweeney Jr, W E; Kepka, D M et al. (1991) Localization of arginine biosynthetic enzymes in renal proximal tubules and abundance of mRNA during development. Pediatr Res 29:151-4

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