Structure and organization of amplified DNA on double minutes containing the mdm2 oncogene.
We have been studying a transformed derivative of a mouse fibroblast line (3T3DM) that stably maintains double minute chromosomes (DMs). In this report we describe a comprehensive analysis of the structure of the DMs within this cell line, utilizing a combination of long-range mapping via pulsed-field gel electrophoresis, screening of DM-enriched genomic libraries, and DM sizing using contour-clamped homogeneous electric field (CHEF) gel electrophoresis. Our data indicate that the minute particles in these cells exist as a homogeneous population of circular molecules, roughly 4 Mb in size, upon which three genes are amplified. One of these is the mdm2 oncogene, which has also been found to be amplified in a number of human sarcomas. Further, we present evidence that these three genes are arranged as two identical inverted repeat units linked by spacer regions of heterogeneous size. This work has led to the first model for the structure of an entire double minute particle containing an amplified oncogene; this model provides clues to later events occurring in the gene amplification process in tumor cells.
Fakharzadeh
S S
SS
Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia 19104-6145.
Rosenblum-Vos
L
L
Murphy
M
M
Hoffman
E K
EK
George
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DL
D016475:3T3 Cells; D000818:Animals; D002461:Cell Line, Transformed; D004247:DNA / Q000235:genetics*; D015226:Dinucleoside Phosphates / Q000032:analysis; D005784:Gene Amplification; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins; D009857:Oncogenes; D011518:Proto-Oncogene Proteins; D051736:Proto-Oncogene Proteins c-mdm2; D012093:Replicon
D004247:DNA; D015226:Dinucleoside Phosphates; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D051736:Proto-Oncogene Proteins c-mdm2; C015772:CpG dinucleotide; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse