In 1993 Victor Ambros finds a tiny RNA called lin-4 in a worm, and colleagues treat it as a curiosity. By 2001 the same kind of molecule appears in every animal examined, and in 2024 Ambros and Gary Ruvkun receive the Nobel Prize.
The Visitor follows one of these small RNAs to its target.
A Second Layer of Regulation
- The ENCODE project (2012) established that 80% of the human genome has biochemical activity, compared with about 2% that codes for protein.
- Three regulators carry the story. MicroRNAs (21 to 23 nucleotides) bind messenger RNA by a seed match and bring in the RISC complex. The page reports about 2,000 human miRNAs regulating about 60% of protein-coding genes. Long regulatory RNAs (lncRNA, over 200 nucleotides) scaffold chromatin complexes, and the 17 kb XIST molecule silences an entire X chromosome across 155 Mbp. Riboswitches bind metabolites such as SAM, TPP, and adenine and control translation directly.
- The page describes miRNA regulation as three parts working together: the miRNA gene, the RISC machinery, and the target sites in messenger RNA.
- The page sets two reading systems side by side on one genome: the genetic code reads the sense strand in triplets, and the miRNA system reads short segments and matches them to regulatory regions.
The small RNA finds its seed match on the message and the RISC ring closes around the site. The site page carries all three regulators.
Which RNA regulator binds a metabolite directly and controls translation?
The riboswitch.
The genome carries a second layer of regulation written in RNA, running alongside the protein recipes.
The Visitor lights node 07 and the map connects it to Ribozymes.
See the map