3,5,3'-Triiodothyronine-induced carbamyl-phosphate synthetase gene expression is stabilized in the liver of Rana catesbeiana tadpoles during heat shock.
One of many changes occurring during spontaneous and 3,5,3'-triiodothyronine (T3)-induced metamorphosis of the Rana catesbeiana tadpole is the permanent transition from an ammonotelic, aquatic larva to a ureotelic, terrestrial adult. T3-induced urea production is preceded by T3-induced elevation in the synthesis and level of liver-specific urea cycle enzymes essential for detoxication of ammonia in a terrestrial environment. This report focuses on establishing the effects heat shock (hs) has on the T3-induced expression of genes encoding three essential urea cycle enzymes. We demonstrate that hs stabilizes the intracellular existing levels of carbamyl-phosphate synthetase I (CPS I), the first enzyme in the urea cycle, while concurrently depressing its new synthesis. To establish the effects of hs on CPS I mRNA levels, we characterized cDNAs encoding an amphibian CPS I and demonstrate that it may represent an evolutionary link between microbial CPS and mammalian CPS I. Using this CPS I cDNA and other R. catesbeiana gene-specific probes, we demonstrate that hs depresses the level of T3-induced thyroid hormone receptor beta mRNAs but does not affect the level of T3-induced CPS I, ornithine transcarbamylase, and arginase mRNAs. These results support the contention that the hs response may involve the selective protection of some pre-existing mRNAs and proteins essential for an organism's survival.
Helbing
C C
CC
Department of Zoology, University of Western Ontario, London, Canada.
Atkinson
B G
BG
D000595:Amino Acid Sequence; D000818:Animals; D001119:Arginase / Q000096:biosynthesis; D001483:Base Sequence; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000096:biosynthesis* / Q000235:genetics; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004790:Enzyme Induction; D005293:Ferritins / Q000096:biosynthesis; D015870:Gene Expression / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006358:Hot Temperature; D007814:Larva / Q000201:enzymology; D008099:Liver / Q000201:enzymology*; D008675:Metamorphosis, Biological; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D009954:Ornithine Carbamoyltransferase / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000378:metabolism; D011892:Rana catesbeiana; D011988:Receptors, Thyroid Hormone / Q000096:biosynthesis; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D014284:Triiodothyronine / Q000494:pharmacology*
D012333:RNA, Messenger; D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine; D004247:DNA; D005293:Ferritins; D009954:Ornithine Carbamoyltransferase; D001119:Arginase; D002222:Carbamoyl-Phosphate Synthase (Ammonia)