title: Activation of an enhancerless gene by chromosomal integration.
abstract: Expression of enhancerless (E-) and enhancer-containing (E+) genes that are chromosomally integrated was examined. An E- plasmid (pE-cat) containing a chloramphenicol acetyltransferase (cat) gene linked to the simian virus 40 (SV40) early promoter or its E+ counterpart plasmid (pE+-cat) containing the SV40 enhancer was cotransfected into thymidine kinase (TK)-deficient L cells with a cloned tk gene. A number of TK+ transformants were isolated, and expression of the cointegrated cat gene in these cell lines was quantitatively determined by the assay of CAT activity. The results indicated unexpectedly that the E- cat gene was as actively expressed as the E+ cat gene. Analysis of CAT mRNA by primer extension indicated that the E- cat gene, as well as the E+ cat gene, was transcribed from the "native" initiation site contained in the SV40 early promoter region. The active expression of the E- cat gene was maintained in secondary TK+ transformants that arose by transfection with genomic DNA from the primary transformant. These results suggest that expression of the integrated E- cat gene is activated by endogenous enhancer elements.
mesh_terms: D000123:Acetyltransferases / Q000235:genetics; D000818:Animals; D015500:Chloramphenicol O-Acetyltransferase; D002875:Chromosomes / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D005796:Genes; D005809:Genes, Regulator; D005814:Genes, Viral; D008040:Genetic Linkage; D007739:L Cells / Q000378:metabolism; D051379:Mice; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D013539:Simian virus 40 / Q000235:genetics; D018139:Simplexvirus / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D012333:RNA, Messenger; D000123:Acetyltransferases; D015500:Chloramphenicol O-Acetyltransferase; D013937:Thymidine Kinase