Evidence of an Unusual Poly(A) RNA Signature Detected by High-Throughput Chemical Mapping

Homopolymeric adenosine RNA plays numerous roles in both cells and noncellular genetic material. We report herein an unusual poly(A) signature in chemical mapping data generated by the Eterna Massive Open Laboratory. Poly(A) sequences of length seven or more show unexpected results in the selective 2'-hydroxyl acylation read out by primer extension (SHAPE) and dimethyl sulfate (DMS) chemical probing. This unusual signature first appears in poly(A) sequences of length seven and grows to its maximum strength at length ∼10. In a long poly(A) sequence, the substitution of a single A by any other nucleotide disrupts the signature, but only for the 6 or so nucleotides on the 5' side of the substitution.