Escherichia coli DNA polymerase II is stimulated by DNA polymerase III holoenzyme auxiliary subunits

DNA polymerase III of Escherichia coli requires multiple auxiliary factors to enable it to serve as a replicative complex. We demonstrate that auxiliary components of the DNA polymerase III holoenzyme, the γδ complex and β subunit, markedly stimulate DNA polymerase II on long single-stranded templates. DNA polymerase II activity is enhanced by single-stranded DNA binding protein, but the stimulation by γδ and β can be observed either in the absence or presence of single-stranded DNA binding protein. In contrast with DNA polymerase III, the requirement of DNA polymerase II for γδ cannot be bypassed by large excesses of the β subunit at low ionic strength in the absence of the single-stranded DNA binding protein. The product of the DNA polymerase II-γδ-β reaction on a uniquely primed single-stranded circle is of full template length; the reconstituted enzyme apparently is incapable of strand displacement synthesis. The possible biological implications of these observations are discussed.