Ribonuclease III (RNase III or RNase C)(BREND
3.1.26.3
is a type of

ribonuclease Ribonuclease (commonly abbreviated RNase) is a type of nuclease that catalyzes the degradation of RNA into smaller components. Ribonucleases can be divided into endoribonucleases and exoribonucleases, and comprise several sub-classes within the ...

that recognizes dsRNA and cleaves it at specific targeted locations to transform them into mature RNAs. These enzymes are a group of endoribonucleases that are characterized by their ribonuclease domain, which is labelled the RNase III domain. They are ubiquitous compounds in the cell and play a major role in pathways such as RNA precursor synthesis, RNA Silencing, and the ''pnp'' autoregulatory mechanism.

Types of RNase III

The RNase III superfamily is divided into four known classes: 1, 2, 3, and 4. Each class is defined by its domain structure.Liang Y-H, Lavoie M, Comeau M-A, Elela SA, Ji X. Structure of a Eukaryotic RNase III Post-Cleavage Complex Reveals a Double- Ruler Mechanism for Substrate Selection. Molecular cell. 2014;54(3):431-444. doi:10.1016/j.molcel.2014.03.006. Class 1 RNase III *Class 1 RNase III enzymes have a homodimeric structure whose function is to cleave dsRNA into multiple subunits. It is a Mg²⁺-dependent endonuclease and is largely found in

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

and

bacteriophage A bacteriophage (), also known informally as a ''phage'' (), is a duplodnaviria virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν ('), meaning "to devour". Bac ...

. Class 1 RNase III have been found in Glomeromycotan

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

, which was suspected to be the result of

horizontal gene transfer Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offspring (reproduction). H ...

from

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, bl ...

. Among the RNases III in the class are the rnc from '' E. coli''. Typically, class I enzymes possess a single RNase III domain (RIIID) followed by a dsRNA-binding domain (). They process precursors to

ribosomal RNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from riboso ...

(rRNA),

small nuclear RNA Small nuclear RNA (snRNA) is a class of small RNA molecules that are found within the splicing speckles and Cajal bodies of the cell nucleus in eukaryotic cells. The length of an average snRNA is approximately 150 nucleotides. They are transcribe ...

(snRNA) and

small nucleolar RNA In molecular biology, Small nucleolar RNAs (snoRNAs) are a class of small RNA molecules that primarily guide chemical modifications of other RNAs, mainly ribosomal RNAs, transfer RNAs and small nuclear RNAs. There are two main classes of snoRNA, t ...

(snoRNA). The basic dsRNA cleavage function of Class 1 RNase III is retained in most of the organisms in which it is present. However, in a number of species the function has changed and taken on different or additional biological roles. ::Rnc (UniProtK
P0A7Y0
-

E.Coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Esche ...

- this RNase III is involved in the processing of viral transcripts and some mRNAs through the cleavage of multiple areas on the dsRNA. This cleavage can be influenced by

ribosomal protein A ribosomal protein (r-protein or rProtein) is any of the proteins that, in conjunction with rRNA, make up the ribosomal subunits involved in the cellular process of translation. ''E. coli'', other bacteria and Archaea have a 30S small subunit an ...

presence. ::The variances of Class 1 RNase III, calle
Mini-III
are homodimeric enzymes and consist solely of the RNase III domains. Class 2 RNase III 4OOG

* Class II is defined by the presence of an N-terminal domain (NTD), a RIIID, and a . Class II is found in some fungi species. They process precursors to rRNA, snRNA, and snoRNA. :Yeast nucleases with the Class 2 RNase III domain: ::RNT1 (UniProtK
Q02555
-

S. cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been o ...

- this RNase III is involved in the transcription and processing of rDNA, the 3' end formation of U2 snRNA via cleavage of the terminal loop, cell wall stress response and degradation, and regulation of morphogenesis checkpoint genes. ::Pac1 (UniProtK
P22192
- S. pombe - this RNase III is located on chromosome II of the yeast nuclease and when over expressed, is directly involved in the sterility, lack of mating efficiency, abnormal mitotic cell cycle, and mutation suppression of the organism. Class 3 RNase III 5b16 drosha dgcr8

* Class 3 RNases III include the Drosha family of enzymes known to function in maturation of precursors to microRNA (miRNA). Class 4 RNase III * Class 4 RNases III include the Dicer family of enzymes known to function in

RNA interference RNA interference (RNAi) is a biological process in which RNA molecules are involved in sequence-specific suppression of gene expression by double-stranded RNA, through translational or transcriptional repression. Historically, RNAi was known by ...

(RNAi). Class 4 III RNases are S-RNase components. It is a component of the self-incompatibility system in Rosaceae, Solanaceae, and Plantaginaceae. They are recruited to cope with various environmental stress scenarios. *Dicer enzymes process dsRNA substrates into small RNA fragments of individual size ranging from 21-27 nucleotides in length. Dicer has an N-terminal helicase/ATPase domain which is followed by another domain of an unknown function. It also comprises the centrally positioned PAZ domain and a C-terminal configuration which includes one and two RNase III catalytic domains. Interactions of Dicer occurs with other proteins, which includes TRBP, PACT, and Ago2. RNAs that are produced by Dicer act as guides for a sequence of particular silencing of cognate genes through RNAi and related pathways.

Types of RNase III

Human proteins containing RNase III domain

See also

References

External links