期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1982
卷号：79
期号：12
页码：3697-3701
DOI：10.1073/pnas.79.12.3697
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Recombinant plasmids carrying a segment of Xenopus laevis chromosomal DNA were constructed with plasmid pBR322 as the vector. A recombinant plasmid pXY65 carrying a 3.2-kilobase BamHI segment of the chromosome of X. laevis has been found to contain a repetitive sequence dispersed throughout the X. laevis chromosomes. This plasmid initiated replication in vitro when the supercoiled circular molecules were incubated in a replication system. The other recombinant plasmids tested and the pBR322 vector were not replicated. Electron microscopic analysis of the replicative intermediates showed that the replication was initiated at a specific site in the 3.2-kilobase BamHI segment of pXY65 and that the replication usually proceeded bidirectionally. Analysis of the reaction products by centrifugation in alkaline sucrose gradients indicated that short pieces were synthesized in the in vitro replication system. DNA synthesis was inhibited in vitro by the addition of aphidicolin and by omission of dNTPs. These results indicate that the X. laevis segment cloned in pXY65 contains a site capable of initiating replication in vitro.
