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Spontaneous and induced production of endogenous type‐C RNA virus from a clonal line of spontaneously transformed BALB/3T3
Author(s) -
Lieber Michael M.,
Todaro George J.
Publication year - 1973
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910110313
Subject(s) - biology , virus , endogeny , cell culture , 3t3 cells , virology , microbiology and biotechnology , endogenous retrovirus , clone (java method) , titer , antigen , transfection , genome , gene , genetics , biochemistry
This report describes the different levels of expression of the endogenous type‐C viral genome in a spontaneously transformed, tumor‐producing clone (S16) derived from the BALB/3T3 murine cell line. Four of nine subclones of S16 were found to continuously release high titers of endogenous virus. Five other S16 subclones were virus‐nonproducers, but could be readily induced with 5′‐bromodeoxyuridine to release large quantities of the endogenous virus. The transformed subclones were much more readily induced to produce virus compared to the parent BALB/3T3 cell line. All virus‐producing subclones and one non‐virus‐producing subclone contained considerably larger quantites of the major group‐specific antigens of the mouse type‐C viruses than did the untransformed BALB/3T3 cells themselves. Kinetics of induction of type‐C virus was studied in two clones that did not spontaneously release virus. Extracellular viral polymerase could be detected within 24 h of BrdU application; it increased exponentially over a thousand‐fold range during the next 48 h, and then slowly declined. Thus, the probability of expression of the endogenous type‐C viral genome is increased in spontaneously transformed BALB/3T3 cells.