Estrogen Regulates Vitellogenin Gene Transcription and Messenger-Rna Degradation in Xenopus Laevis Liver
Brock, Martin Louis
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https://hdl.handle.net/2142/70523
Description
Title
Estrogen Regulates Vitellogenin Gene Transcription and Messenger-Rna Degradation in Xenopus Laevis Liver
Author(s)
Brock, Martin Louis
Issue Date
1983
Department of Study
Biochemistry
Discipline
Biochemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Biochemistry
Abstract
Vitellogenin gene transcription and mRNA degradation rates were measured in Xenopus laevis liver using pulse labeling and pulse chase techniques. Estrogen regulates the accumulation of vitellogenin mRNA through three processes: (1) There is a selective transcriptional activation of the vitellogenin genes from an essentially off mode to a completely on mode within 6-8 hr of the addition of estrogen. (2) Estrogen causes a selective 30 fold stabilization of vitellogenin mRNA over general mRNA sequences. In the absence of estrogen, vitellogenin mRNA displays normal degradation kinetics. (3) The rate of total RNA synthesis increases in the presence of estrogen 20-60 fold. The selective effect of estrogen on vitellogenin transcription does not require de novo protein synthesis. The increased rate of vitellogenin mRNA accumulation in secondary stimulation is mediated by a four fold enhancement of the relative rate of vitellogenin transcription as well as by an increase in total RNA synthesis. After several days of estrogen stimulation, vitellogenin mRNA reaches a plateau value. This plateau is caused by a reduction in total RNA synthesis and not by a change in the relative rate of transcription of the vitellogenin genes. Degradation of vitellogenin mRNA is also regulated in a direct manner in that protein synthesis is not required to shift vitellogenin mRNA from a state of stability to a state of instability. These regulatory states are reversible, so the existence of a diffusable stabilizing species is proposed. The total rate of RNA synthesis is regulated only indirectly by estrogen. Numerous observations of a correlation between nucleoside triphosphates and the rate of RNA synthesis has led to a proposal of an etiological connection between them.
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