Special Topic: Frontiers in RNA Research: The ever-expanding RNA world.

Abstract

RNA is perhaps the most mystical molecule in life. As a single molecule endowed with both informational and catalytic capacities, it was proposed by Alexander Rich 52 years ago to be the first molecule that self-replicated at the origin of life, to be taken over by DNA only later. Although this ‘RNA world’ (vividly phrased by Walter Gilbert in 1986) remains an enticing yet unproven hypothesis, the crucial roles of messenger RNAs (mRNAs), transfer RNAs (tRNAs), and ribosomal RNAs (rRNAs) in transcribing and translating genetic information into proteins and, in turn, life processes have been indisputably established and extensively illustrated in the past half-century, as elegantly simplified in the central dogma of molecular biology. The discovery of microRNAs (miRNAs) and small interfering RNAs (siRNAs) since early 1993 further enriched the dogma by revealing that these two classes of small non-coding RNAs mediate new mechanisms that regulate the turnover and translation of mRNAs. In the past 10 years, the advent of the DNA deep-sequencing technology further allowed the discovery of an even larger RNA world full of various types of novel non-coding RNAs, such asmillions of Piwi-interacting RNAs (piRNAs) and thousands of long non-coding RNAs (lncRNAs).