Doctoral Dissertations

Date of Award

12-1985

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biomedical Sciences

Major Professor

Francis T. Kennedy

Committee Members

Peter A. Lalley, Wen K. Yang, Ken Volkin, K. Bruce Jacobson

Abstract

Two genes, tyrosine aminotransferase (TAT) and another as of yet unidentified gene referred to as gene 33, expressed in rat liver and subject there to control by several hormones and to regulation of expression during differentiation of the liver have been of particular interest due to the similarities in the control of their expression in rat liver. Extensive research has been focused on the expression of these two genes in rat liver but the tissue specificity of their expression has not been explored. Immunochemical analyses of partially purified protein from nonhepatic tissued utilizing TAT specific antibodies and analyses of RNA in nonhepatic tissues using a cDNA clone for TAT revealed that TAT is expressed only in the liver. In contrast to TAT, hybridization analyses of gene 33 RNA in nonhepatic tissues using a cDNA clone demonstrated that this gene is expressed at varying levels in kidney, brain, heart, lung, and testis. Uniform size mRNA, 3.4kb, was detected in each of these tissues and the mRNA was present in the cytoplasm where it has the potential to be translated into a protein product. Several hormonal agents known to regulate expression of gene 33 in rat liver, cAMP, insulin, and hydrocortisone, were investigated for their effect on expression in these tissues. Both cAMP and insulin increased the levels of gene 33 mRNA in kidney and liver. On the other hand, hydrocortisone effectively elevated the gene 33 mRNA in each of the tissues. In vitro transcription runoff assays in hydrocortisone-induced kidney nuclei determined that the mechanism by which hydrocortisone exerts its action in kidney is via increased transcription, as was previously shown for its action on liver. In summary, two rat genes subject to similar multihormonal and developmental expression in rat liver were found to be differentially expressed in nonhepatic tissues.

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