The process of RNA interference (RNAi) can be moderated by either siRNA or miRNA, but there are subtle differences between the two. Both are processed inside the cell by the enzyme called Dicer and incorporated into a complex called RISC. siRNA, however, is considered exogenous double-stranded RNA that is taken up by cells, or enters via vectors like viruses, while miRNA is single stranded and comes from endogenous (made inside the cell) non-coding RNA, found within the introns of larger RNA molecules.
Another difference is that, in animals, siRNA typically binds perfectly to its mRNA target, a perfect match to the sequence, whereas miRNA can inhibit translation of many different mRNA sequences because its pairing is imperfect. In plants, miRNA tends to have a more perfectly complimentary sequence which induces mRNA cleavage as opposed to just repression of translation.
The process of RNA interference (RNAi) can be moderated by either siRNA or miRNA, but there are subtle differences between the two. Both are processed inside the cell by the enzyme called Dicer and incorporated into a complex called RISC. siRNA, however, is considered exogenous double-stranded RNA that is taken up by cells, or enters via vectors like viruses, while miRNA is single stranded and comes from endogenous (made inside the cell) non-coding RNA, found within the introns of larger RNA molecules.
Another difference is that, in animals, siRNA typically binds perfectly to its mRNA target, a perfect match to the sequence, whereas miRNA can inhibit translation of many different mRNA sequences because its pairing is imperfect. In plants, miRNA tends to have a more perfectly complimentary sequence which induces mRNA cleavage as opposed to just repression of translation.
Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA molecules, 20-25 base pairs in length. siRNA plays many roles, but its most notable is in the RNA interference (RNAi) pathway, where it interferes with the expression of specific genes with complementary nucleotide sequence. siRNA also acts in RNAi-related pathways, e.g., as an antiviral mechanism or in shaping the chromatin structure of a genome. The complexity of these pathways is only now being elucidated.
A microRNA (miRNA) is a small non-coding RNA molecule (22 nucleotides) found in plants and animals, which functions in transcriptional and post-transcriptional regulation of gene expression. Encoded by eukaryotic nuclear DNA, miRNAs function via base-pairing with complementary sequences within mRNA molecules, usually resulting in gene silencing via translational repression or target degradation.