Cell fusion-mediated improvement in transfection competence for repair-deficient mutant of mouse T cell line

A multiple mutagen-sensitive mutant (XUM1) of mouse T-cell lymphoma line, L5178Y, is hypersensitive to ionizing radiation, ultraviolet (UV) light, and cross-linking agents (such as mitomycin C). The frequency of transfection for XUM1 cells after exposure to calcium phosphate-coprecipitated pSV2neo DNA was more than 10(4)-fold less effective than that for Ltk-aprt- (LTA) cells. Other transfection methods (DEAE-dextran and polybrene-DMSO) were not effective for L5178Y and XUM1 cells. The transfection-proficient trait of LTA cells was demonstrated to be genetically dominant by examining the the transfection frequency in hybrid clones constructed between XUM1 and LTA cells. To circumvent the problem with XUM1, the LTA genes necessary for transformation processes were introduced into XUM1 cells by constructing hybrids between XUM1 and LTA cells irradiated with X-rays which causes directional chromosome elimination for hybrid cells. Four of 194 hybrid clones tested were transfection-proficient and hypersensitive to UV (XL102, XL107, XL215, and XL216). All four clones were not hypersensitive to X-rays or mitomycin C. The frequencies of transfection for XL102 and XL216 were nearly the same level as that for LTA cells. The efficiency of transfection for XL107 and XL215 was 10 to 100-fold lower than that for LTA cells.