1. The synthesis of
mitochondrial DNA in CEF in vivo at 3,4 and 6 days after
infection with RSV (Schmidt-Ruppin, subgroup A) was progressively stimulated 2 to 4-fold as compared with that in uninfected CEF cells grown in parallel. 2. The stimulation of
mtDNA synthesis in vivo upon transformation was found to be temperature dependent when the thermosensitive mutant of RSV, T5, was used to infect the cells. 3. In contrast to
mtDNA synthesis, nuclear
DNA synthesis did not differ in transformed and uninfected cells, nor did it change significantly upon temperature shifts. 4.
MtDNA (monomeric and catenated dimeric forms) in transformed and uninfected CEF replicate by displacement synthesis. Various replication intermediates are described. 5. The
restriction endonuclease EcoRI cleaves closed circular
mtDNA from CEF at one specific site. 6. Heteroduplex molecules formed between nicked circular and/or EcoRI cleaved mt
DNA molecules from uninfected and transformed CEF revealed, with a few exceptions, no detectable base sequence heterogeneity in at least 98% of cases. 7. Intramitochondrial virus like particles (IMV) are described in hamster
tumor cells. The evidence suggests both engulfment of cytoplasmic particles by mitochondria and the presence of intramitochondrial incomplete forms of particles.
Bromodeoxyuridine was found to enhance the frequency of IMV.