title: Replication initiates in a broad zone in the amplified CHO dihydrofolate reductase domain.
abstract: We have used two complementary two-dimensional gel electrophoretic methods to localize replication inititation sites and to determine replication fork direction in the amplified 240 kb dihydrofolate reductase domain of the methotrexate-resistant CHO cell line CHOC 400. Surprisingly, our analysis indicates that replication begins at many sites in several restriction fragments distributed throughout a previously defined 28 kb initiation locus, including a fragment containing a matrix attachment region. Initiation sites were not detected in regions lying upstream or downstream of this locus. Our results suggest that initiation reactions in mammalian chromosomal origins may be more complex than in the origins of simple microorganisms.
authors.affiliation: Department of Biochemistry, University of Virginia School of Medicine, Charlottesville 22908.
authors.forename: J P
authors.initials: JP
authors.lastname: Vaughn
authors.forename: P A
authors.initials: PA
authors.lastname: Dijkwel
authors.forename: J L
authors.initials: JL
authors.lastname: Hamlin
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D004261:DNA Replication; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D005784:Gene Amplification; D010053:Ovary; D015183:Restriction Mapping; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*; D014162:Transfection
chemical_list: D004247:DNA; D013762:Tetrahydrofolate Dehydrogenase