The pattern of dihydrofolate reductase expression through the cell cycle in rodent and human cultured cells

We have examined the pattern of dihydrofolate reductase (DHFR) enzyme and mRNA levels in cell cycle stage-specific populations obtained by centrifugal elutriation in Chinese hamster ovary cells and in a derivative line in which the dihydrofolate reductase gene is amplified approximately 50-fold. On...

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Bibliographic Details
Published in:The Journal of biological chemistry 1989-12, Vol.264 (34), p.20583-20590
Main Authors: Feder, J.N., Assaraf, Y.G., Seamer, L.C., Schimke, R.T.
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Blotting, Northern
Cell Cycle
Cell Line
Cells, Cultured
Cricetinae
DNA - analysis
Flow Cytometry
Fundamental and applied biological sciences. Psychology
Gene Expression
Genes
Humans
Mice
Molecular and cellular biology
Molecular genetics
RNA, Messenger - analysis
RNA, Messenger - genetics
Tetrahydrofolate Dehydrogenase - genetics
Tetrahydrofolate Dehydrogenase - metabolism
Transcription, Genetic
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Summary:We have examined the pattern of dihydrofolate reductase (DHFR) enzyme and mRNA levels in cell cycle stage-specific populations obtained by centrifugal elutriation in Chinese hamster ovary cells and in a derivative line in which the dihydrofolate reductase gene is amplified approximately 50-fold. On a per cell basis, we observed a 2-fold increase in DHFR activity as cells progressed from G1 to G2/M with a concomitant 2-fold increase in the rate of protein synthesis and steady state level of mRNA. Analysis of DHFR mRNA levels in cell cycle stage-specific mouse 3T6 and human 143 tk- cells gave a similar pattern. We also demonstrate that simple alterations in growth conditions prior to elutriations can dramatically increase the levels of DHFR mRNA in all cell cycle states, thereby indicating that growth response associated with the DHFR gene functions independent of the cell cycle. We conclude that during periods of exponential growth the increases in dihydrofolate reductase activity, rate of protein synthesis, and steady state levels of mRNA parallel the general increases in cell volume and protein content associated with normal progression through the cell cycle, and therefore DHFR cannot be considered a cell cycle-regulated enzyme.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(19)47102-0