Reichard P, Eliasson R, Söderman G
Proc Natl Acad Sci U S A. 1974 Dec;71(12):4901-5. doi: 10.1073/pnas.71.12.4901.
During replication of polyoma DNA in isolated nuclei, RNA was found attached to the 5' ends of growing progeny strands. This RNA starts with either ATP or GTP and can be labeled at its 5' end with (32)P from beta-labeled nucleotides. Digestion of progeny strands with pancreatic DNase released (32)P-labeled RNA that, on gel electrophoresis, gave a distinct peak in the position expected for a decanucleotide. We believe that this short RNA is involved in the initiation of the discontinuous synthesis of DNA and propose the name "initiator RNA" for it. The covalent linkage of initiator RNA to 5' ends of growing DNA chains was substantiated by the finding that (32)P was transferred to ribonucleotides by alkaline hydrolysis of purified initiator RNA obtained by DNase digestion of polyoma progeny strands synthesized from [alpha-(32)P]dTTP. While initiator RNA was quite homogeneous in size, it had no unique base sequence since digestion with pancreatic RNase of initiator RNA labeled at its 5' end with (32)P released a variety of different [(32)P]oligonucleotides. The switch from RNA to DNA synthesis during strand elongation may thus depend on the size of initiator RNA rather than on a specific base sequence.
在多瘤病毒DNA于分离细胞核中复制期间，发现RNA附着于正在生长的子代链的5'末端。这种RNA以ATP或GTP起始，并且其5'末端可用来自β标记核苷酸的（32）P进行标记。用胰脱氧核糖核酸酶消化子代链会释放出（32）P标记的RNA，该RNA在凝胶电泳上，在十聚核苷酸预期的位置给出一个明显的峰。我们认为这种短RNA参与DNA的不连续合成起始，并为此提议将其命名为“引发RNA”。引发RNA与正在生长的DNA链5'末端的共价连接通过以下发现得到证实：通过对由[α-（32）P]dTTP合成的多瘤病毒子代链进行脱氧核糖核酸酶消化而获得的纯化引发RNA进行碱性水解，（32）P被转移到核糖核苷酸上。虽然引发RNA在大小上相当均匀，但它没有独特的碱基序列，因为用胰核糖核酸酶消化5'末端用（32）P标记的引发RNA会释放出各种不同的[（32）P]寡核苷酸。因此，链延伸过程中从RNA合成到DNA合成的转变可能取决于引发RNA的大小，而不是特定的碱基序列。
