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A temperature-sensitive DNA synthesis mutant isolated from the Chinese hamster ovary cell line
1School of Life and Health Sciences, University of Delaware, Newark 19711, USA.
Abstract:
A temperature-sensitive DNA synthesis mutant, tsC8, was isolated from mutagenized Chinese hamster ovary cells by the fluorodeoxyuridine suicide technique. The tsC8 cells showed inhibition of DNA synthesis at the nonpermissive temperature (NPT) with little effect on initial levels of RNA and protein synthesis. Temperature-arrested tsC8 cells had G1 or S DNA content and the temperature-sensitive (ts) period of the tsC8 cell cycle was the interval between the G1/S border and the middle of the S period. The tsC8 cells were unable to enter the S phase when exposed to the NPT during the G1 period of the cell cycle. When S phase tsC8 cells were shifted to the NPT, they incorporated [3H]thymidine at rates similar to the parental cell type for only 2 h, indicating a ts defect in DNA synthesis. The tsC8 mutation is expressed in a recessive manner and is in a gene distinct from those affected in other DNA synthesis mammalian cell mutants.
Insights
Researchers identified a new temperature-sensitive DNA synthesis mutant, tsC8, in Chinese hamster ovary cells. This mutant specifically impairs DNA replication at elevated temperatures, offering insights into cell cycle regulation and DNA repair mechanisms.
Area of Science:
- Cell Biology
- Genetics
- Molecular Biology
Background:
- DNA synthesis is crucial for cell division and is tightly regulated.
- Mutants with defects in DNA synthesis provide valuable tools for studying cell cycle control.
- Chinese hamster ovary (CHO) cells are a widely used model system in mammalian cell genetics.
Purpose of the Study:
- To isolate and characterize a novel temperature-sensitive mutant defective in DNA synthesis.
- To determine the specific cell cycle phase affected by the mutation.
- To investigate the genetic properties and potential novelty of the mutation.
Main Methods:
- Isolation of temperature-sensitive mutants using the fluorodeoxyuridine suicide technique.
- Assessment of DNA, RNA, and protein synthesis at permissive and non-permissive temperatures.
- Cell cycle analysis of mutant cells.
- Analysis of [3H]thymidine incorporation to measure DNA synthesis rates.
Main Results:
- A temperature-sensitive mutant, tsC8, was isolated from mutagenized CHO cells.
- tsC8 cells exhibited inhibited DNA synthesis at the non-permissive temperature, with minimal impact on RNA and protein synthesis.
- The temperature-sensitive period was identified as the G1/S border to mid-S phase.
- Mutant cells were unable to enter S phase when shifted to the non-permissive temperature during G1.
- DNA synthesis defect was confirmed by short-term [3H]thymidine incorporation assays.
Conclusions:
- The tsC8 mutation confers a specific defect in DNA synthesis during the G1/S transition and early S phase.
- The mutation is recessive and located in a gene distinct from previously characterized DNA synthesis mutants.
- tsC8 represents a valuable new tool for dissecting the molecular mechanisms of DNA replication and cell cycle control in mammalian cells.