Schematic of a possible gene regulatory network via sgRNA and tRNase Z^L.

<p>Small RNA degradation products from tRNA or rRNA can work as sgRNA for tRNase Z^L, which exists ubiquitously in cells including mitochondria [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118631#pone.0118631.ref009" target="_blank">9</a>]. These RNAs may be also working as signaling molecules between cells.