Muller W J, Mueller C R, Mes A M, Hassell J A
J Virol. 1983 Sep;47(3):586-99. doi: 10.1128/JVI.47.3.586-599.1983.
To define the minimal cis-acting sequences required for polyomavirus DNA replication (ori), we constructed a number of polyomavirus-plasmid recombinants and measured their replicative capacity after transfection of a permissive mouse cell line capable of providing polyomavirus large T antigen in trans (MOP cells). Recombinant plasmids containing a 251-base-pair fragment of noncoding viral DNA replicate efficiently in MOP cells. Mutational analyses of these viral sequences revealed that they can be physically separated into two genetic elements. One of these elements, termed the core, contains an adenine-thymine-rich area, a 32-base-pair guanine-cytosine-rich palindrome, and a large T antigen binding site, and likely includes the site from which bidirectional DNA replication initiates. The other, termed beta, is located adjacent to the core near the late region and is devoid of outstanding sequence features. Surprisingly, another sequence element named alpha, located adjacent to beta but outside the borders of the 251-base-pair fragment, can functionally substitute for beta. This sequence too contains no readily recognized sequence features and possesses no obvious homology to the beta element. The three elements together occupy a contiguous noncoding stretch of DNA no more than 345 base pairs in length in the order alpha, beta, and core. These results indicate that the polyomavirus origin for DNA replication comprises multiple genetic elements.
为了确定多瘤病毒DNA复制所需的最小顺式作用序列（ori），我们构建了许多多瘤病毒 - 质粒重组体，并在转染了能够反式提供多瘤病毒大T抗原的允许性小鼠细胞系（MOP细胞）后测量了它们的复制能力。含有251个碱基对的非编码病毒DNA片段的重组质粒在MOP细胞中能高效复制。对这些病毒序列的突变分析表明，它们可在物理上分为两个遗传元件。其中一个元件称为核心，包含富含腺嘌呤 - 胸腺嘧啶的区域、一个32个碱基对的富含鸟嘌呤 - 胞嘧啶的回文序列以及一个大T抗原结合位点，并且可能包括双向DNA复制起始的位点。另一个元件称为β，位于晚期区域附近核心的相邻位置，没有突出的序列特征。令人惊讶的是，另一个名为α的序列元件，位于β相邻但在251个碱基对片段边界之外，在功能上可以替代β。该序列也不包含容易识别的序列特征，并且与β元件没有明显的同源性。这三个元件一起占据了一段连续的非编码DNA片段，长度不超过345个碱基对，顺序为α、β和核心。这些结果表明，多瘤病毒DNA复制起点由多个遗传元件组成。
