Linear simian virus 40 DNA fragments exhibit a propensity for rolling-circle replication.

A linear simian virus 40 origin-containing DNA fragment replicated in monkey COS cells, generating tandemly repeated (head-to-tail) structures. Electron microscopy revealed circle-and-tail configurations characteristic of rolling-circle replication intermediates. Circularization of the same DNA before transfection led to a theta type of replication which generated supercoiled DNA molecules.