Dicer is a type of Ribonuclease that processes potentially harmful double-stranded RNA (dsRNA) into microRNA and small-interfering RNA (siRNA) to be used in the process of RNA interference. Dicer is commonly utilized by cells in order to prevent the assimilation of viral DNA into the cells’ genome. The viral DNA is butchered into smaller segments that are each about 21 nucleotides long; the cut take places at the 5’ phosphate and the 3’ hydroxyl, and usually includes a 2 nucleotide overhang. There is a single processing center in HS Dicer implying that there are two catalytic sites which help form products with the 2 3' overhang. These newly formed segments attach themselves to single stranded mRNA which ultimately leads to mRNA degradation by the cell and translational suppression. The dicer enzyme in humans contains two domains the RNase IIIa and the RNase IIIb. There are three classes of RNase III proteins which are divided into categories called Escherichia coli RNase III, Drosha, and Dicer which are given the numbers one, two, and three respectively. The Escherichia coli RNase III class has one domain while the Drosha and dicer have two domains each. There is no evidence of the first class of enzymes in mammals.
Paz Domain
RNase III 1
RNase III 2
Structure
Human Dicer (hDicer) is a dimer. Each chain is a large multidomain enzyme whose C-terminal half includes a PAZ domain, a pair of tandem RNase III domains, and a double-stranded RNA-binding domain. There are four magnesium ions that bind to the hDicer RNase IIIb homodimer. There are oxygen ligands bonded to each Magnesium, which create an octahedral geometry on each Magnesium. The amino acids amino acids present on the oxygen ligands are Glutamic Acid and Aspartic Acid.
