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Ribonuclease 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 EC 2.7 and 3.1 classes of enzymes.
Ribonuclease H is a family of non-sequence-specific endonuclease enzymes that catalyze the cleavage of RNA in an RNA/DNA substrate via a hydrolytic mechanism. Members of the RNase H family can be found in nearly all organisms, from bacteria to archaea to eukaryotes.
Retrotransposons are a type of genetic component that copy and paste themselves into different genomic locations (transposon) by converting RNA back into DNA through the reverse transcription process using an RNA transposition intermediate.
Ranpirnase is a ribonuclease enzyme found in the oocytes of the Northern Leopard Frog. Ranpirnase is a member of the pancreatic ribonuclease protein superfamily and degrades RNA substrates with a sequence preference for uracil and guanine nucleotides. Along with amphinase, another leopard frog ribonuclease, Ranpirnase has been studied as a potential cancer and antiviral treatment due to its unusual mechanism of cytotoxicity tested against transformed cells and antiviral activity.
Transcriptional modification or co-transcriptional modification is a set of biological processes common to most eukaryotic cells by which an RNA primary transcript is chemically altered following transcription from a gene to produce a mature, functional RNA molecule that can then leave the nucleus and perform any of a variety of different functions in the cell. There are many types of post-transcriptional modifications achieved through a diverse class of molecular mechanisms.
Ribonuclease P is a type of ribonuclease which cleaves RNA. RNase P is unique from other RNases in that it is a ribozyme – a ribonucleic acid that acts as a catalyst in the same way that a protein-based enzyme would. Its function is to cleave off an extra, or precursor, sequence of RNA on tRNA molecules. Further, RNase P is one of two known multiple turnover ribozymes in nature, the discovery of which earned Sidney Altman and Thomas Cech the Nobel Prize in Chemistry in 1989: in the 1970s, Altman discovered the existence of precursor tRNA with flanking sequences and was the first to characterize RNase P and its activity in processing of the 5' leader sequence of precursor tRNA. Recent findings also reveal that RNase P has a new function. It has been shown that human nuclear RNase P is required for the normal and efficient transcription of various small noncoding RNAs, such as tRNA, 5S rRNA, SRP RNA and U6 snRNA genes, which are transcribed by RNA polymerase III, one of three major nuclear RNA polymerases in human cells.
Ribonuclease III (RNase III or RNase C)(BRENDA 3.1.26.3) is a type of ribonuclease 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.
Drosha is a Class 2 ribonuclease III enzyme that in humans is encoded by the DROSHA gene. It is the primary nuclease that executes the initiation step of miRNA processing in the nucleus. It works closely with DGCR8 and in correlation with Dicer. It has been found significant in clinical knowledge for cancer prognosis and HIV-1 replication.
RNase MRP is an enzymatically active ribonucleoprotein with two distinct roles in eukaryotes. RNAse MRP stands for RNAse for mitochondrial RNA processing. In mitochondria it plays a direct role in the initiation of mitochondrial DNA replication. In the nucleus it is involved in precursor rRNA processing, where it cleaves the internal transcribed spacer 1 between 18S and 5.8S rRNAs. Despite distinct functions, RNase MRP has been shown to be evolutionarily related to RNase P. Like eukaryotic RNase P, RNase MRP is not catalytically active without associated protein subunits.
In molecular biology, nuclear ribonuclease P is a ubiquitous endoribonuclease, found in archaea, bacteria and eukarya as well as chloroplasts and mitochondria. Its best characterised enzyme activity is the generation of mature 5′-ends of tRNAs by cleaving the 5′-leader elements of precursor-tRNAs. Cellular RNase Ps are ribonucleoproteins. The RNA from bacterial RNase P retains its catalytic activity in the absence of the protein subunit, i.e. it is a ribozyme. Similarly, archaeal RNase P RNA has been shown to be weakly catalytically active in the absence of its respective protein cofactors. Isolated eukaryotic RNase P RNA has not been shown to retain its catalytic function, but is still essential for the catalytic activity of the holoenzyme. Although the archaeal and eukaryotic holoenzymes have a much greater protein content than the bacterial ones, the RNA cores from all three lineages are homologous—the helices corresponding to P1, P2, P3, P4, and P10/11 are common to all cellular RNase P RNAs. Yet there is considerable sequence variation, particularly among the eukaryotic RNAs.
An exoribonuclease is an exonuclease ribonuclease, which are enzymes that degrade RNA by removing terminal nucleotides from either the 5' end or the 3' end of the RNA molecule. Enzymes that remove nucleotides from the 5' end are called 5'-3' exoribonucleases, and enzymes that remove nucleotides from the 3' end are called 3'-5' exoribonucleases.
Pancreatic ribonuclease family is a superfamily of pyrimidine-specific endonucleases found in high quantity in the pancreas of certain mammals and of some reptiles.
Exoribonuclease II is an enzyme. This enzyme catalyses the following chemical reaction
The degradosome is a multiprotein complex present in most bacteria that is involved in the processing of ribosomal RNA and the degradation of messenger RNA and is regulated by Non-coding RNA. It contains the proteins RNA helicase B, RNase E and Polynucleotide phosphorylase.
In enzymology, an alanine—tRNA ligase is an enzyme that catalyzes the chemical reaction
In enzymology, a tRNA nucleotidyltransferase is an enzyme that catalyzes the chemical reaction
Ribonuclease pancreatic is an enzyme that in humans is encoded by the RNASE1 gene.
Ribonuclease H1 also known as RNase H1 is an enzyme that in humans is encoded by the RNASEH1 gene. The RNase H1 is a non-specific endonuclease and catalyzes the cleavage of RNA via a hydrolytic mechanism.
Ribonuclease E is a bacterial ribonuclease that participates in the processing of ribosomal RNA and the chemical degradation of bulk cellular RNA.
Ribonuclease V1 is a ribonuclease enzyme found in the venom of the Caspian cobra. It cleaves double-stranded RNA in a non-sequence-specific manner, usually requiring a substrate of at least six stacked nucleotides. Like many ribonucleases, the enzyme requires the presence of magnesium ions for activity.
References
- ↑ Sekiya T, Contreras R, Takeya T, Khorana HG (July 1979). "Total synthesis of a tyrosine suppressor transfer RNA gene. XVII. Transcription, in vitro, of the synthetic gene and processing of the primary transcript to transfer RNA". The Journal of Biological Chemistry. 254 (13): 5802–16. PMID 109442.
