Cloned cat cells (CCC) transformed by the ml isolate of Moloney murine sarcoma virus (MSV) have the properties of sarcoma-positive, leukemia-negative (S+L-) cells. Over the past 5 years, partially flat as well as very contact-inhibited variant cloneswere isolated from several clonal generations of S+l— cat cells. Partially flat subclones still contained the MSV genome and could serve as useful cell systems for quantal assays for a number of replicating retroviruses. The frequency of isolation of rescue-negative, very flat subclones diminished with sequential cloning cycles of S+l—cells. The rescue-negative revertant cells grew to low density in liquid media, were more similar to normal cells in soft-agar colony formation, and were intermediate in concanavalin A agglutinability when compared to normal or S+l- cells. Revertants could be retransformed by pseudotypes of MSV other than MSV coated with feline endogenous xenotropic virus. Feline endogenous xenotropic virus was readily induced from S+L-cells but was not inducible from some revertants by halogenated pyrimidines. Rescue-negative revertants could support the growth of a number of helper viruses. Chromosomes of parental CCC normal cells, MSV producer cells, S+l— cells, or revertants were all significantly hypodiploid. No stable pathognomonic changes were observed relative to type and chromosome number among the above. The MSV-coded precursor polyprotein with a molecular weight of 60,000 was detected in producer and S+l— cells but not detected in revertants. Producer and S+l- cells had multiple MSV src copies in their DNA, whereas revertants did not contain residual src DNA. The number of either feline endogenous xenotropic virus or feline leukemia virus-like DNA copies was not different amongproducer, S + L-, or revertant cells. Accordingly, all rescue-negative cat cell revertants tested have lost multiple copies of MSV proviral DNA.
|Original language||English (US)|
|Number of pages||8|
|State||Published - Mar 1 1981|
ASJC Scopus subject areas
- Cancer Research