TABLE 1.

Specific activity of various Pol preparations

Reaction mixtures (10 μl) contained 20 mm Tris-HCl, pH 7.5, 0.2 mm DTT, 100 μg/ml BSA, 50 μm [α−³²P]dTTP (3400 cpm/pmol), 2 mm ATP, 0.2 m sodium glutamate (not added with Pol δ), 6 nm hRFC, 100 nm hPCNA, 350 nm E. coli SSB, 25 μm (as nucleotides), poly(dA)₄₀₀₀-oligo(dT)_12–18 (20:1). Variable levels of Pols were incubated for 20 min at 37 °C, and nucleotide incorporation was measured.

Protein preparation	Specific activity	Turnovera
	μmol/h/mg protein	pmol incorporated/min/pmol protein
S. cerevisiae Pol ϵ	120	690
hPol δ	51	212
p261N	29	48.3
p261-FL	14	60.1
p261-p59	12	88.5
4S hPol ϵ (four-subunit)	10	72
p261-p12-p17	14	68

^a Turnover refers to pmol of nucleotide incorporated/min/pmol of protein. S. cerevisiae Pol ϵ assays were carried out using S. cerevisiae RFC/S. cerevisiae PCNA in place of the human homologs.