Answer to Question #293080 in Cell Biology for Margo

Question

The amino acid asparagine is synthesized from aspartic acid by the enzyme asparagine synthetase (AS).

Propose a scheme where a cell can regulate the expression of AS. Include a figure clearly diagramming the regulation mechanism.

Your scheme should account for the concentrations of asparagine and aspartic acid.

Answer 1

the asparagine synthetase (AS) gene in ts11 cells, a mutant of BHK hamster cells which encodes a temperature-sensitive AS and therefore does not produce endogenous asparagine at 39.5 degrees C. Incubation of ts11 cells at the nonpermissive temperature drastically increases the level of AS mRNA, and the stimulation of AS mRNA expression is effectively suppressed by the addition of asparagine to the medium. We show here that regulation of AS gene expression involves cis-acting elements which are contained in the mRNA as well as in the 5' genomic region. When a plasmid containing the human AS cDNA under the control of the human AS promoter region was stably transfected into ts11 cells, the expression of human AS RNAs was regulated as that of the endogenous hamster transcripts,