Detection of a DNA polymerase β stimulating protein in hela cell nuclear extracts

HeLa cell nuclei contain a protein which stimules the $\text{in}\text{vitro}$ activity of HeLa cell DNA polymerase β, but does not affect the activity of DNA polymerase α and γ. The protein, which binds to both single- and double-stranded DNA, does not possess nuclease activity and is heat stable, surviving 100 degrees C for 10 min. The molecular weight of the protein is approximately 85,000 and evidence is presented that it may exert its stimulatory effect by direct interaction with β-polymerase.