Ariizumi K, Ariga H
Mol Cell Biol. 1986 Nov;6(11):3920-7. doi: 10.1128/mcb.6.11.3920-3927.1986.
A small circular DNA was found extrachromosomally in a clone of F9 embryonal carcinoma (EC) cells at high copy numbers per cell. The DNA was cloned in plasmid pUC19. Restriction endonuclease analyses of the DNA indicated that the DNA (fPyF9) was a mutant of polyomavirus (Py) DNA and had a mutation in a noncoding regulatory region. There have been many reports on the isolation of Py mutants capable of replication in undifferentiated cells. However, fPyF9 was different from other Py mutants in the following aspects: it was harbored stably as a free copy at 1 X 10(4) to 5 X 10(4) copies per cell in EC cells; it replicated in undifferentiated cells better than in differentiated cells; it was extremely rearranged in the sequences of the enhancer B domain; and it carried in the enhancer B domain three copies of an exogenous sequence which does not exist in Py strain A2. From these observations, we propose a new class of Py EC mutant which has an autonomous state similar to that of plasmid and small circular DNA in host cells.
在F9胚胎癌细胞克隆中，发现一种小环状DNA以每个细胞高拷贝数存在于染色体外。该DNA被克隆到质粒pUC19中。对该DNA的限制性内切酶分析表明，该DNA（fPyF9）是多瘤病毒（Py）DNA的突变体，且在一个非编码调控区域存在突变。关于能够在未分化细胞中复制的Py突变体的分离已有许多报道。然而，fPyF9在以下方面与其他Py突变体不同：它在EC细胞中以每个细胞1×10⁴至5×10⁴个拷贝的游离拷贝形式稳定存在；它在未分化细胞中的复制能力优于分化细胞；它在增强子B结构域的序列中极度重排；并且它在增强子B结构域中携带了三个Py A2株中不存在的外源序列拷贝。基于这些观察结果，我们提出了一类新的Py EC突变体，其在宿主细胞中具有类似于质粒和小环状DNA的自主状态。
