Liposome-mediated insertion of intact DNA into isolated nuclei. Potential for a new in vitro transcription system

DNA molecules sequestered within negatively charged liposomes became nuclei-associated following interaction between isolated mouse plasmacytoma nuclei and liposomes. Few if any liposomes appeared to adhere to washed nuclei following their interaction with liposomes, suggesting that DNA was internalized. Liposome-delivered, radioactive pBR322 DNA re-extracted from nuclei appeared intact, whereas DNA from nuclei incubated with naked DNA was degraded. Up to 2 × 10¹⁰ D of DNA were inserted into each nucleus. DNA delivered into nuclei via liposome was transcribed as shown by the fact that about 1% of the RNA synthesized in nuclei injected with pBR322 or E. coli DNA hybridized with moderate excess of homologous DNA. pBR322-specific RNA synthesized in isolated nuclei consisted of large MW transcripts. Experiments in which SV40 DNA and pBR322 DNA were delivered simultaneously in equimolar amounts into nuclei indicated that SV40 DNA was transcribed as efficiently as pBR322 DNA.