5tRFs

5tRFs (5' tRNA-derived fragments) are a class of small non-coding RNAs derived from the 5' end of mature transfer RNAs. They are part of the broader tRNA-derived fragment (tRF) family and are distinct from tRNA halves (tiRNAs) produced by cleavage in the anticodon loop. 5tRFs are typically 14–30 nucleotides long, depending on the tRNA and organism, and can be generated under normal conditions as well as during cellular stress.

Biogenesis and properties: 5tRFs arise when specific ribonucleases cleave mature tRNAs near the 5' end, producing a fragment from the 5' end. Enzymes implicated in 5tRF production include angiogenin and Dicer in some systems, though the exact enzymes and pathways vary among species. 5tRFs can be stable in cells and can associate with RNA-binding proteins, and in certain contexts they are found associated with Argonaute proteins, enabling miRNA-like regulation.

Functions and roles: 5tRFs can regulate gene expression at post-transcriptional levels, influence translation initiation, and modulate mRNA stability. In some cases they act in a manner similar to microRNAs, guiding silencing complexes to target transcripts, while in others they affect ribosome biogenesis or translation directly by interacting with ribosomes or initiation factors.

Research and significance: 5tRFs have been detected in diverse organisms, including humans, and have been found in intracellular and extracellular compartments. They have been implicated in development and stress responses, and there is interest in their roles as biomarkers or therapeutic targets in cancer and neurodegenerative diseases. Ongoing work seeks to clarify their biogenesis pathways, target spectra, and context-dependent functions.