Reiter T, Fett R, Knippers R
Eur J Biochem. 1987 Apr 1;164(1):59-63. doi: 10.1111/j.1432-1033.1987.tb10992.x.
Protein extracts were prepared at various times after serum stimulation of growth-arrested mouse 3T3 fibroblasts. The extracts were fractionated by sucrose gradient centrifugation and used to determine the activities of DNA polymerase alpha and DNA primase. We found that polymerase and primase appeared in close association in one homogeneous 8.2-S peak. Neither polymerase, free of associated primase, nor primase, free of polymerase, could be detected at any time after serum stimulation. The activities of both enzymes started to increase concomitantly at the beginning of the DNA replication phase of the cell cycle. We found five to six times more DNA primase activity in replicating than in resting 3T3 cells. Besides DNA primase, a second additional priming activity could be detected. This activity sedimented at 12.5 S and corresponded most probably to RNA polymerase I.
在血清刺激生长停滞的小鼠3T3成纤维细胞后的不同时间制备蛋白质提取物。提取物通过蔗糖梯度离心进行分级分离，并用于测定DNA聚合酶α和DNA引发酶的活性。我们发现聚合酶和引发酶在一个均匀的8.2-S峰中紧密相关。在血清刺激后的任何时间，均未检测到不含相关引发酶的聚合酶或不含聚合酶的引发酶。两种酶的活性在细胞周期的DNA复制阶段开始时同时开始增加。我们发现，正在复制的3T3细胞中的DNA引发酶活性比静止细胞中的高五到六倍。除了DNA引发酶外，还可检测到第二种额外的引发活性。该活性在12.5 S处沉降，最有可能对应于RNA聚合酶I。
