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Differences between normal and transformed murine fibroblasts in the expression of various promoter/enhancer—chloramphenicol acetyltransferase constructs
Author(s) -
Begemann Martin,
Hsiao W.L. Wendy,
Weinstein I. Bernard
Publication year - 1988
Publication title -
molecular carcinogenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.254
H-Index - 97
eISSN - 1098-2744
pISSN - 0899-1987
DOI - 10.1002/mc.2940010308
Subject(s) - chloramphenicol acetyltransferase , biology , enhancer , transfection , microbiology and biotechnology , cell culture , retrovirus , acetyltransferase , gene , dna , gene expression , endogeny , cell , reporter gene , genetics , acetylation , biochemistry
High levels of poly(A)+ RNAs homologous to certain endogenous retrovirus‐related DNA sequences are frequently seen in carcinogen‐transformed rodent cells. To explore the underlying mechanism, transient expression assays were done to determine whether carcinogen‐ or radiation‐transformed C3H 10T1/2 cell lines differ from normal 10T1/2 cells in terms of their ability to express the chloramphenicol acetyltransferase (CAT) gene when it is linked to various promoter/enhancer sequences, including two independently isolated intracisternal A particle (IAP) long terminal repeat sequences designated prcm and pMIA6. We found that with several constructs, CAT activity was always 3‐ to 10‐fold higher in the transformed 10T1/2 cell lines than in the normal 10T1/2 cells. The prcm‐CAT construct displayed the highest CAT activity in both the normal and transformed C3H 10T1/2 cells. Studies with 32 P‐labeled prcm‐CAT DNA and Southern blot analyses indicated that the differences in CAT activity between normal and transformed cells were not due to greater uptake or retention of the transfected DNA by the transformed cells. Competition studies provided evidence that factors required for the expression of the prcm‐CAT construct are present in limited amounts in normal 10T1/2 cells and in excess amounts in transformed 1011/2 cells. These putative factors may play a role in the increased expression of endogenous retrovirus‐related sequences in the transformed cells.