Conaway R C, Lehman I R
Proc Natl Acad Sci U S A. 1982 Apr;79(8):2523-7. doi: 10.1073/pnas.79.8.2523.
Preparations of DNA polymerase alpha from early embryos of Drosophila melanogaster catalyze the ATP-dependent synthesis of DNA with single-stranded M13 DNA or poly(dT) templates. In the case of M13 DNA, GTP, but not UTP or CTP, can replace ATP. The reaction is completely dependent on added template and is not inhibited by alpha-amanitin. Alkaline hydrolysis of the product synthesized in the presence of [alpha-32P]dATP and poly(dT) generates 32P-labeled 3'(2') adenylate, showing that a covalent ribo-deoxynucleotide linkage is formed. Furthermore, incorporation of ribonucleotides occurs at the 5' end of the newly synthesized polynucleotide chain. These findings are consistent with the hypothesis that a ribo-oligonucleotide primer is synthesized by primase action and subsequently elongated by DNA polymerase. Under the appropriate conditions, DNA polymerase I from Escherichia coli can elongate primers formed by primase in the presence of ATP and poly(dT). Primase activity copurifies with DNA polymerase alpha and may be part of the multisubunit polymerase molecule.
从黑腹果蝇早期胚胎中制备的DNA聚合酶α，能以单链M13 DNA或聚（dT）为模板催化依赖ATP的DNA合成。以M13 DNA为模板时，GTP可替代ATP，而UTP或CTP则不能。该反应完全依赖于添加的模板，且不受α-鹅膏蕈碱抑制。在[α-32P]dATP和聚（dT）存在下合成的产物经碱性水解，产生32P标记的3'（2'）腺苷酸，表明形成了共价的核糖-脱氧核苷酸连接。此外，核糖核苷酸掺入新合成的多核苷酸链的5'末端。这些发现与以下假设一致：核糖寡核苷酸引物由引发酶作用合成，随后由DNA聚合酶延伸。在适当条件下，大肠杆菌的DNA聚合酶I能在ATP和聚（dT）存在下延伸由引发酶形成的引物。引发酶活性与DNA聚合酶α共纯化，可能是多亚基聚合酶分子的一部分。
