[Nuclear reconstitution around purified E. coli DNA in cell-free extracts of Xenopus laevis eggs]

In recent years we have succeeded in inducing various exogenous DNA to assembly typical nuclei in cell-free Xenopus egg extracts. However, it is not clear if prokaryotic chromosomal DNA can also form the nucleus in this eukaryotic system. In our experiment, we used the purified E. coli. chromosomal DNA to reconstitute the nucleus in the nuclear reconstitution extracts and found that typical nuclei can also be assembled around added DNA. We observed the process of nuclear reconstitution by using light microscopy and electronic microscopy. The scanning results of chromatin-like materials and assembled nuclei by microspectrophotometer showed that E. coli, chromosal DNA underwent obvious change from condensation to decondensation during nuclear reconstitution. Incorporation of alpha-32P-dCTP into DNA suggested that the reconstituted nuclei were capable of DNA replication.