Loss of P53 heterozygosity is not responsible for the small colony thymidine kinase mutant phenotype in L5178Y mouse lymphoma cells.
The mouse lymphoma L5178Y Tk+/- 3.7.2C assay is a well-characterized in vitro system used for the study of somatic cell mutation. It was determined that this cell line has a heterozygous mutation in exon 5 of Trp53. Based on this assumption that the cell line is heterozygous for the Trp53 gene, it was postulated that the small colony thymidine kinase (Tk) mutant phenotype may be due to a newly induced mutation/deletion in both the Trp53 and Tk1 alleles. The resultant Tk-/- mutants would also be Trp53+/0 or Trp53+/+ and would lose their ability to grow at normal rates. Subsequently, we published our evaluation of the Trp53 status in L5178Y cells. This analysis included sequencing of Trp53 exon 4 and determined that the mouse lymphoma cell line has a mutation in both of the Trp53 alleles and, therefore, no wild-type Trp53 allele in either Tk+/- cells or Tk-/- mutants. Because the cells have no wild-type Trp53, it is not possible that the small colony phenotype results from a newly induced loss of both functional Trp53 and Tk. To determine whether small colonies might, however, include the deletion of both Trp53 and Tk we evaluated, using microsatellite marker analysis, a series of small colony mutants. We also utilized in situ hybridization to determine that the Trp53 alleles are, in fact, in their normal chromosome 11 location in Tk+/- 3.7.2C mouse lymphoma cells. From all of these analyses we can conclude that the small colony mutant phenotype is not caused by deletion of both Trp53 and Tk1.
Clark
L Scott
LS
University of North Carolina Curriculum in Toxicology, University of North Carolina, Chapel Hill, NC, USA.
Harrington-Brock
Karen
K
Wang
Jianyong
J
Sargent
Linda
L
Lowry
David
D
Reynolds
Steve H
SH
Moore
Martha M
MM
D000818:Animals; D045744:Cell Line, Tumor; D020223:Chromosome Painting; D004273:DNA, Neoplasm / Q000235:genetics; D005091:Exons; D017353:Gene Deletion; D016158:Genes, p53; D007940:Leukemia L5178 / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D019656:Loss of Heterozygosity; D051379:Mice; D018895:Microsatellite Repeats; D009154:Mutation; D010641:Phenotype; D013937:Thymidine Kinase / Q000235:genetics*
D004273:DNA, Neoplasm; D013937:Thymidine Kinase