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Cyclic AMP as a transcriptional inhibitor of upper eukaryotic gene transcription
Abstract:
Recently, glucagon and its second messenger, cyclic AMP, have been shown to stimulate the transcription rate of several upper eukaryotic genes (1-5). We show here that glucagon can also block gene transcription. Both glucagon and cyclic AMP were found to inhibit the transcription of the genes encoding three liver glycolytic enzymes, including L-type pyruvate kinase and aldolase B. Thus, cyclic AMP proves to be not only an activator but also an inhibitor of gene transcription in eukaryotes.
Insights
Glucagon and cyclic AMP, known gene activators, can also inhibit gene transcription. This study demonstrates their dual role by showing they block the transcription of key liver glycolytic enzyme genes.
Area of Science:
- Molecular Biology
- Biochemistry
- Gene Regulation
Background:
- Glucagon and cyclic AMP (cAMP) are recognized for stimulating eukaryotic gene transcription.
- The precise regulatory roles of cAMP in gene expression are complex and multifaceted.
Purpose of the Study:
- To investigate the inhibitory effects of glucagon and cAMP on gene transcription.
- To determine if cAMP acts solely as a transcriptional activator or also as an inhibitor.
Main Methods:
- Analysis of gene transcription rates in response to glucagon and cAMP.
- Focus on genes encoding liver glycolytic enzymes, specifically L-type pyruvate kinase and aldolase B.
Main Results:
- Glucagon was found to inhibit the transcription of specific genes.
- Cyclic AMP also demonstrated an inhibitory effect on the transcription of these genes.
- The transcription of genes for L-type pyruvate kinase and aldolase B was suppressed.
Conclusions:
- Glucagon and cyclic AMP possess dual roles in eukaryotic gene transcription, acting as both activators and inhibitors.
- Cyclic AMP's function extends beyond transcriptional activation to include inhibition.
- These findings reveal a more complex regulatory mechanism for glycolytic enzyme gene expression.