Biomaterial Database

DNA replication initiates at multiple sites on plasmid DNA in Xenopus egg extracts. 1992

H M Mahbubani, and T Paull, and J K Elder, and J J Blow

ICRF Clare Hall Laboratories, Potters Bar, Herts, UK.

Cell-free extracts of Xenopus eggs will replicate plasmid DNA molecules under normal cell cycle control. We have used the neutral/neutral 2-D gel technique to map the sites at which DNA replication initiates in this system. Three different plasmids were studied: one containing the Xenopus rDNA repeat, one containing single copy Xenopus genomic DNA, and another containing the yeast 2 microns replication origin. 2-D gel profiles show that many potential sites of initiation are present on each plasmid, and are randomly situated at the level of resolution of this technique (500-1000 bp). Despite the abundance of sites capable of supporting the initiation of replication, pulse-chase experiments suggest that only a single randomly situated initiation event occurs on each DNA molecule. Once initiation has taken place, conventional replication forks appear to move away from this site at a rate of about 10nt/second, similar to the rate observed in vivo.

UI	MeSH Term	Description	Entries
D010063	Ovum	A mature haploid female germ cell extruded from the OVARY at OVULATION.	Egg,Egg, Unfertilized,Ova,Eggs, Unfertilized,Unfertilized Egg,Unfertilized Eggs
D010957	Plasmids	Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.	Episomes,Episome,Plasmid
D002457	Cell Extracts	Preparations of cell constituents or subcellular materials, isolates, or substances.	Cell Extract,Extract, Cell,Extracts, Cell
D004261	DNA Replication	The process by which a DNA molecule is duplicated.	Autonomous Replication,Replication, Autonomous,Autonomous Replications,DNA Replications,Replication, DNA,Replications, Autonomous,Replications, DNA
D004275	DNA, Ribosomal	DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.	Ribosomal DNA,rDNA
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D014982	Xenopus laevis	The commonest and widest ranging species of the clawed "frog" (Xenopus) in Africa. This species is used extensively in research. There is now a significant population in California derived from escaped laboratory animals.	Platanna,X. laevis,Platannas,X. laevi
D015180	Electrophoresis, Gel, Two-Dimensional	Electrophoresis in which a second perpendicular electrophoretic transport is performed on the separate components resulting from the first electrophoresis. This technique is usually performed on polyacrylamide gels.	Gel Electrophoresis, Two-Dimensional,Polyacrylamide Gel Electrophoresis, Two-Dimensional,2-D Gel Electrophoresis,2-D Polyacrylamide Gel Electrophoresis,2D Gel Electrophoresis,2D PAGE,2D Polyacrylamide Gel Electrophoresis,Electrophoresis, Gel, 2-D,Electrophoresis, Gel, 2D,Electrophoresis, Gel, Two Dimensional,Polyacrylamide Gel Electrophoresis, 2-D,Polyacrylamide Gel Electrophoresis, 2D,Two Dimensional Gel Electrophoresis,2 D Gel Electrophoresis,2 D Polyacrylamide Gel Electrophoresis,Electrophoresis, 2-D Gel,Electrophoresis, 2D Gel,Electrophoresis, Two-Dimensional Gel,Gel Electrophoresis, 2-D,Gel Electrophoresis, 2D,Gel Electrophoresis, Two Dimensional,PAGE, 2D,Polyacrylamide Gel Electrophoresis, 2 D,Polyacrylamide Gel Electrophoresis, Two Dimensional,Two-Dimensional Gel Electrophoresis