Unstable amplification of the chromosomal gene for 3-hydroxy-3-methylglutaryl coenzyme A reductase in compactin-resistant CR200 cells.
CR200 cells, a compactin-resistant clone of mouse FM3A cells, overaccumulate 3-hydroxy-3-methylglutaryl coenzyme A reductase. The elevated reductase activity is not regulated normally by low-density lipoprotein, mevalonate and 25-hydroxycholesterol. The amounts of reductase protein and mRNA were elevated in CR200 cells by 40- to 60-fold, as compared to those in parental FM3A cells and the rate of reductase transcription and the number of copies of reductase gene were increased in CR200 cells by 20- to 50-fold. In the parental cells, mevalonate and 25-hydroxycholesterol suppressed reductase transcription by greater than 90%, while that in the mutant cells was suppressed by only 20-50%, suggesting a regulatory alteration in the gene transcription in CR200 cells. When CR200 cells were grown for 10-20 weeks in the absence of compactin, levels of the gene amplification were reduced from approx. 50-fold to approx. 2-fold, along with a marked decrease in reductase activity and compactin-resistance of the cells. While the gene amplification was unstable, minute chromosomes were not seen in the cells and centrifugal fractionation and in situ analysis demonstrated that the amplified reductase gene was present on 2-3 chromosomes in the pseudotetraploidal CR200 cells having approx. 78 chromosomes. From these results it was concluded that the amplified reductase gene, which is responsible for overaccumulation of reductase, is located on chromosomes but is unstable in CR200 cells.
Hasumi
K
K
Department of Applied Biological Science, Tokyo Noko University, Japan.
Naganuma
S
S
Sato
Y
Y
Endo
A
A
D000818:Animals; D002458:Cell Fractionation; D002460:Cell Line / Q000187:drug effects / Q000201:enzymology; D015342:DNA Probes; D004351:Drug Resistance; D005784:Gene Amplification / Q000187:drug effects*; D006903:Hydroxymethylglutaryl CoA Reductases / Q000096:biosynthesis / Q000235:genetics*; D007621:Karyotyping; D008148:Lovastatin / Q000031:analogs & derivatives / Q000494:pharmacology; D008677:Metaphase; D051379:Mice; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000032:analysis
D015342:DNA Probes; D012333:RNA, Messenger; C012258:mevastatin; D008148:Lovastatin; D006903:Hydroxymethylglutaryl CoA Reductases