Derivation of Tk- Clones from Revertant Tk+ Mammalian Cells
AUTOR(ES)
Roufa, D. J.
RESUMO
In order to obtain a large collection of Chinese hamster cell clones defective in thymidine kinase (TK-), BrdUr selection experiments have been performed on wild-type and revertant TK+ cell lines. No clones (< 10-9) were obtained from the wild-type TK+ cell line by single-step selection. In contrast, revertant TK+ clones readily gave rise to stable TK- derivatives (1 - 2 x 10-4). Both wild-type and revertant TK+ clones spontaneously yielded 8-AGr colonies with the same frequency (1 - 5 x 10-6), suggesting that the differences between wild-type and revertant cell lines specifically affected selection of the TK- phenotype. The increased frequency of TK- clones reflects perhaps the number (ploidy) or character of the autosomal TK loci in TK+ revertants, or perhaps the mechanisms which regulate expression of the TK genes. Several mutagens, EMS, MNNG and UV, stimulated the TK+ revertants' frequency of TK- subclones only slightly (< 3-fold). Biochemical and genetic data indicated that the TK- clones derived from one revertant are phenotypically different. The phenotypes displayed by these cell lines are stable and do not depend upon the continued presence of the selective agent.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1213025Documentos Relacionados
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