Biebricher C K, Eigen M, McCaskill J S
Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
J Mol Biol. 1993 May 20;231(2):175-9. doi: 10.1006/jmbi.1993.1271.
In the absence of extraneously added templates, Q beta replicase produces different RNA species after long lag times spontaneously in vitro. The sequences of the spontaneous products are short (30 to 45 nucleotides) and bear little sequence relation to one another and no detectable sequence homology to Q beta virus RNA or to the host. Their replication rates are much lower than those of optimized products. Incubation without template in long closed capillaries produces after long lag times many separate RNA growth foci with heterogeneous kinetics. The template-free reaction is strongly dependent on the conditions: lowering the enzyme or the triphosphate concentrations abolishes the template-free RNA synthesis without affecting the template-dependent synthesis. An explanation of the emerging RNA species in template-free reactions by residual RNA contaminants in the incubation mixture is very unlikely in the light of the experimental evidence; however, the experimental evidence is fully compatible with a de novo mechanism (which may include instruction by non-replicatable oligonucleotides).
在没有额外添加模板的情况下，Qβ复制酶在体外长时间滞后后会自发产生不同的RNA种类。自发产物的序列很短（30至45个核苷酸），彼此之间几乎没有序列关系，与Qβ病毒RNA或宿主也没有可检测到的序列同源性。它们的复制速率远低于优化产物。在长封闭毛细管中无模板孵育，经过长时间滞后后会产生许多具有异质动力学的独立RNA生长位点。无模板反应强烈依赖于条件：降低酶或三磷酸浓度会消除无模板RNA合成，而不影响模板依赖性合成。根据实验证据，认为孵育混合物中残留的RNA污染物导致无模板反应中出现RNA种类的解释极不可能；然而，实验证据与从头合成机制（可能包括不可复制的寡核苷酸的指导）完全相符。
