Nucleic acid polymerases of the developing chicken embryo: a DNA polymerase preferring a hybrid template

This paper presents a preliminary survey of the nucleic acid polymerases of the developing chicken embryo, especially of the 4-day stage. The predominant activity is that of a DNA polymerase preferring a DNA-RNA hybrid as the template. The enzyme, which is activated by Mn(2+) ions and inhibited by p-chloromercuriphenylsulfonate, copies preferentially the ribo strand of a hybrid, such as poly(rA).poly(dT), but is relatively inactive with all-ribo duplexes. DNA polymerase I of Escherichia coli was also found to use the hybrid template with high efficiency, copying preferentially the ribo strand. With the chicken enzyme, the template activity of denatured DNA was increased tenfold by simultaneous transcription with RNA polymerase. DNA polymerase activity reaches a maximum in the 6- to 8-day chicken embryo and then declines progressively to about one-third of the maximal value in the adult chicken.