DNA of minute virus of mice: self-priming, nonpermuted, single-stranded genome with a 5'-terminal hairpin duplex

Abstract

The genome of the nondefective parvovirus minute virus of mice (MVM) is a linear DNA molecular weight 1.48 x 10(6), which is single stranded for approximately 94% of its length. In contrast to the genomes from defective parvoviruses MVM DNA does not contain a detectable inverted terminal redundancy. A combination of enzymatic and physical techniques has shown that the molecule contains a stable hairpin duplex of approximately 130 base pairs located at the 5' terminus of the genome. MVM DNA is efficiently utilized as a template-primer by a number of DNA polymerases, including reverse transcriptases. Polymerases lacking 5' to 3' exonuclease activity yield a duplex DNA product with a molecular weight 1.96 times that of the viral genome, in which the newly synthesized complementary strand is covalently attached to the template. This duplex contains an internal "nick" that can be sealed by DNA ligase to produce a self-complementary single-strand circle. The MVM DNA duplex is cleaved twice by EcoR-RI restriction endonuclease to yield three distinct fragments in molar amounts. These results suggest that the initiation of DNA synthesis in vitro occurs at a point within 100 bases of the 3' end of the genome, using the 3' terminus of viral DNA as a primer, and that the sequence of nucleotides in the genome is not permuted.