TABLE 1.

Virus production after transfection of permissive cells with wild-type or mutant MVM DNA clones^a

Indicator cell line	Virus titers (hybridization U/transfected culture) for producer cell line and virus DNA clone
	A9			NBK
	pMVM	pMVM-E2F	pMVM-Ets	pMVM	pMVM-E2F	pMVM-Ets
A9	8 × 105	ND	9 × 105	4 × 105	ND	4 × 105
NBK	9 × 105	ND	9 × 105	8 × 105	ND	9 × 105

^aCultures of 10⁶ A9 or NBK cells were transfected with 10 μg of DNA of the wild-type (pMVM) or mutant (pMVM-E2F and pMVM-Ets) MVM genomic clones. Cells and supernatants were collected 7 days after transfection and sonicated in order to release progeny viruses. After elimination of cell debris, virus titers were determined by single-cell DNA hybridization, with A9 or NBK indicator cultures. Data shown are average values from five independent experiments (standard deviation < 10%). The background value detected with the replication-deficient MVM genomic clone (pMVMori⁻) was subtracted. ND, nondetectable (<3 U/transfected culture).