真核细胞染色质对单链DNA的高效复制。
Highly efficient copying of single-stranded DNA by eukaryotic cell chromatin.
作者信息
Kaftory A, Fry M
出版信息
Nucleic Acids Res. 1978 Jul;5(7):2679-93. doi: 10.1093/nar/5.7.2679.
Chromatin prepared from S phase hepatoma tissue culture (HTC) cell incorporates in vitro about 11-14 pmoles [3H]dTMP into DNA in 30 min. Single-stranded DNA added to this chromatin stimulates DNA synthesis more than 40-fold whereas activated DNA enhances it about 60-fold. By contrast, stimulation of DNA synthesis by activated DNA in a crude nuclear extract exceeds the stimulation exerted by denatured DNA by a factor of 7. Stimulation of DNA synthesis by denatured DNA is not due to stabilization of either the chromatin or the product of the endogenous reaction. On the other hand, we find that poly(dC) and poly (dT) enhance DNA synthesis by serving as templates which are copied by chromatin in a true complementary fashion. It seems therefore, that eukaryotic cell chromatin is able to copy single-stranded DNA at a high efficiency. Chromatin of G1 arrested cell copies exogenous templates at a considerably reduced rate. The enzyme responsible for the copying of denatured DNA is tentatively identified as DNA polymerase alpha on the basis of its sensitivity to sulfhydril group blocking, its requirements for ions and failure to copy the ribo strand of oligo(dT) poly(A).
从处于S期的肝癌组织培养（HTC）细胞制备的染色质，在体外30分钟内可将约11 - 14皮摩尔的[³H]dTMP掺入DNA中。添加到这种染色质中的单链DNA可将DNA合成刺激40倍以上，而活化DNA则可将其增强约60倍。相比之下，活化DNA在粗核提取物中对DNA合成的刺激比变性DNA所施加的刺激高7倍。变性DNA对DNA合成的刺激并非由于染色质或内源性反应产物的稳定。另一方面，我们发现聚（dC）和聚（dT）通过作为模板以真正互补的方式被染色质复制来增强DNA合成。因此，真核细胞染色质似乎能够高效复制单链DNA。处于G1期停滞的细胞的染色质以相当低的速率复制外源模板。根据其对巯基阻断的敏感性、对离子的需求以及无法复制寡聚（dT）聚（A）的核糖链，初步确定负责复制变性DNA的酶为DNA聚合酶α。
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