Date of Award

1986

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Abstract

Minute virus of mice (MVM) is a helper-independent parvovirus that contains a linear, single-stranded DNA genome with short self-complementary regions at the termini. During an infection of mouse cells with MVM, a high rate of spontaneous deletion is observed. By hybridization with specific probes, it was determined that a proportion of the deleted DNA genomes had retained both termini but contained an internal deletion. Nucleotide sequence analysis of eight cloned isolates showed that internal deletions had occurred at short direct repeats. Slipped mispairing at a replication fork is a possible mechanism for the generation of these mutants. Deletion formation is apparently independent of the cellular background since several drug treatments and changes of host cell line had no appreciable effect.;Two other specific deletion mutants were excised from gels and examined. Each of the DNA fragments consisted of sequence exclusively from the 3' end of the wild type genome. In addition, both terminated within the same six-base consensus sequence (CT A/T (,2)TC). Since the same recognition site is used by the endonuclease that processes progeny viral strands during the MVM replication cycle, it is postulated that these deletion mutants were generated by site-specific cleavage. Since a CT (A/T)(,2)TC motif is also present near the deletion junctions in the internally deleted mutants, the activity of this enzyme may explain the high spontaneous deletion frequency during an infection with MVM.

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