Molecular characterization of an Indian muntjac cell line deficient in aspects of DNA repair

• Main Author: Somia, Nikunj V.
• Published: University of Edinburgh 1990
• Subjects: 572.8
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.662261

An Indian muntjac cell line, SVM, is deficient in an array of DNA repair processes. It exhibits hypersensitivity to UV irradiation and alkylating agents. SVM was transformed with the DNA virus SV40, and some evidence in the literature suggests that this transformation process may of itself have an effect on the repair phenotype of a cell. In order to investigate this possibility for SVM, a spontaneous UV<SUP>r</SUP> partial revertant was isolated and aspects of the SV40 virus were characterized in the mutant cell line, SVM(M), and the revertant cell line, SVM(R). Investigation of the integration site of SV40 has revealed a change between SVM(M) and SVM(R). This change is due to an amplification of the control region of SV40 (containing an enhancer and an origin of replication) at the viral-cellular DNA junction. This amplification has no effect either qualitatively or quantitatively on the biologically important gene product of SV40, the large T-antigen. This study reveals novel T-antigens in the SVM cell lines apparent at 100kD and 76kD as compared to the reported wild-type produce at 94kD. The nature of the 100kD 'super T-antigen' was established as due to an internal duplication of SV40 sequences. The cellular sequence flanking the amplification was cloned and characterized. Northern blot analysis, utilizing probes generated from this region revealed that this cellular DNA encoded a 11kb transcript which was aberrantly overexpressed in SVM(M) and SVM(R) compared to CDM, a cell line considered normal with respect to its DNA repair capacity. Furthermore, one probe from this region revealed a 2.8kb transcript, which was also abundant in SVM cell lines compared to CDM. This transcript may also differ quantitatively between SVM(M) and SVM(R). In order to investigate whether aberrant overexpression of the 11kb transcript was responsible for the DNA repair phenotype of SVM(M), an experiment to decrease levels of this transcript utilising sense/antisense technology was performed. A model for the cause of the spontaneous reversion event in SVM(R) is discussed, and the means by which overexpression of a transcript can lead to a DNA repair deficient phenotype are considered.