Transfer RNA as a source of small functional RNA.

Since their discovery in the 1950s, transfer RNAs (tRNAs) have been best known as adapter molecules that play a central role in translating genetic information. However, recent biochemical and bioinformatic evidence has led to a previously unexpected conceptual consensus that tRNAs are not always end products; they further serve as a source of small functional RNAs. In many organisms, specific tRNA fragments are produced from mature tRNAs or their precursor transcripts not as random degradation products, but as functional molecules involved in many biological processes beyond translation. In this review, we summarize recent studies of tRNA fragments that have provided new insights into tRNA biology by examining the molecular functions of tRNA fragments and proteins with which they interact.