Corn is a fluorogenic RNA aptamer that forms a high-affinity quasi-symmetric homodimer. The Corn dimer interface binds DFHO, resulting in highly photostable yellow fluorescence. Because of its photostability, Corn would be useful in RNA-based small-molecule biosensors, where quantitative accuracy would be affected by photobleaching. Here we describe a strategy for converting the constitutive Corn dimer into a small-molecule-regulated fluorescent biosensor that detects S-adenosylmethionine (SAM) in vitro and in living cells. We fused the Corn aptamer into a helical stem that was engineered by circularly permuting the SAM aptamer from the SAM-III riboswitch. In the absence of SAM, the Corn portion of this fusion RNA is unable to dimerize. However, upon binding SAM, the RNA dimerizes and binds DFHO. This RNA-based biosensor enables detection of SAM dynamics in living mammalian cells. Together, these data describe a class of RNA-based biosensor based on small-molecule-regulated dimerization of Corn.

中文翻译：

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基于代谢物诱导的RNA二聚化活化的基于荧光RNA的传感器。

玉米是形成高亲和力的准对称同型二聚体的荧光RNA适体。玉米二聚体界面与DFHO结合，产生高度光稳定的黄色荧光。由于其光稳定性，玉米将可用于基于RNA的小分子生物传感器，该传感器的定量准确性会受到光漂白的影响。在这里，我们描述了将本构玉米二聚体转化为可在体外和活细胞中检测S-腺苷甲硫氨酸（SAM）的小分子调节型荧光生物传感器的策略。我们将玉米适体融合到一个螺旋茎中，该螺旋茎是通过从SAM-III核糖开关中循环排列SAM适体而设计的。在没有SAM的情况下，该融合RNA的玉米部分不能二聚。但是，结合SAM后，RNA会二聚并结合DFHO。这种基于RNA的生物传感器能够检测哺乳动物活细胞中的SAM动态。这些数据一起描述了基于小分子调节的玉米二聚化的一类基于RNA的生物传感器。