saRNA stands for 'small activating RNA'. These are small snippets of RNA that inactivate a repressor protein, thus activating transcription of a target gene.
These are also sometimes also called self-amplifying mRNA
(still shortened as saRNA, tho), as they are a subclass of mRNA that can self-replicate to produce more copies within the cell; in fact, some viruses are essentially saRNA. This makes saRNA potentially very useful as a medicine, and tailored saRNA molecules are being developed potential treatment for a number of cancers; likewise, the recent malaria vaccine
is an saRNA vaccine.
saRNAs are a type of Double-stranded RNA (dsRNA), that is, RNA formed with two complementary strands, similar to the DNA (but much much much shorter). Other dsRNAs include small interfering RNA (siRNA) and microRNA (miRNA); these other forms of dsRNAs generally turn off expression of genes.