Expression of ?early? and ?late? viral functions in a somatic cell hybrid between a mouse cell and a spontaneous yielder SV 40-transformed Chinese hamster cell

Abstract

A somatic cell hybrid (Cl. 6d) was originated from the fusion of mouse 3T3-4E) and spontaneous yielder SV 40-transformed Chinese hamster (CHK/SVLP AG) cells. During the early stages of its history, the C1. 6d hybrid underwent a rapid chromosome loss, preferentially loosing hamster chromosomes. This was not a constant tendency of the hybrid cells. As the parental CHK)SVLP AG cells, the hybrid cells were always found 100 per cent SV40 T-antigen positive. While CHK/SVLP AG cells infectious SV 40 DNA, V-antigen and virus were regularly detected, in the hybrid cells only infectious DNA was occasionally detected. This was not due either to the loww of an essential Chinese hamster gene(s) or to the presence of an inhibiting mouse cell component(s); it was apparently the consequence of inability of the cells to properly activate the resident SV 40 genome(s). After superinfection with SV 40 DNA, the hybrid cells-though capable of synthesizing SV 40 V-antigen--were unable to ensure virus assembly. Experimental evidence was obtained suggesting that SV 40 maturation is dependent of a cellular function(s).

Chromosomes Involved in Production of Infectious SV40 Particles in Mouse/SV40-Transformed Chinese Hamster Cell Hybrids

“…As we showed previously [15] the CHK/SVLP AG cell line was regularly found 100% SV40 T-antigen positive. Also the Cl 6d and the different superhybrid clones were always found 100% S V 40 T-antigen positive.…”

“…There was no significant difference between these clones, at least in terms of the total number of Chinese hamster chromosomes identified. These three superhybrid clones were also capable of synthesizing SV40 V-antigen and virus after superinfection [15], Knowing that the Chinese hamster kidney cells, whether transformed or not by SV40, were all potential ly permissive for the virus [11] we thought it was im portant to try and see whether or not certain chromo somal pairs were involved in the expression of viral functions. Therefore, we compared each pair of Chinese hamster chromosomes present in Cl 6d with its evolu tion in Cl 6d.6BU.…”

“…(3) Cl 6d is an established hybrid clone originating from fusion of 3T3-4E and CHK/SVLP AG cells (15).…”

“…We have reported previously isolation of a hybrid cell line (Cl 6d) derived from fusion of mouse 3T3-4E and SV40-transformed Chinese hamster kidney (CHK/ SVLP AG) cells [15]. The hybrid cells were SV40 T-antigcn positive.…”