XB-ART-23834Nucleic Acids Res April 11, 1992; 20 (7): 1457-62.
DNA replication initiates at multiple sites on plasmid DNA in Xenopus egg extracts.
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.
PubMed ID: 1579437
PMC ID: PMC312222
Article link: Nucleic Acids Res
References [+] :
Bakken, Mapping of transcription initiation and termination signals on Xenopus laevis ribosomal DNA. 1982, Pubmed, Xenbase