RNase P

Ribonuclease P (RNase 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 other being the ribosome), the discovery of which earned Sidney Altman and Thomas Cech the Nobel Prize in Chemistry in 1989. In fact, Sidney 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 back in the 70's. 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 RNA genes, 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.

Guide RNA

Trypanosomatid protists and other kinetoplastids have a novel post-transcriptional mitochondrial RNA modification process known as "RNA editing". The mitochondrial genome in these cells consists of 20-50 maxicircles that encode genes and "cryptogenes" (and some gRNAs) and 10-20,000 minicircles that encode gRNAs. All of these molecules are catenated into a giant network of DNA that is situated at the base of the flagellum in the inner compartment of the single mitochondrion.

SmY RNA

SmY ribonucleic acids (SmY RNAs) are a family of small nuclear RNAs found in some species of nematode worms. They are thought to be involved in mRNA trans-splicing.SmY RNAs are about 70-90 nucleotides long and share a common secondary structure, with two stem-loops flanking a consensus binding site for Sm protein.Sm protein is a shared component of spliceosomal snRNPs.

Small nucleolar RNA

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, the C/D box snoRNAs which are associated with methylation, and the H/ACA box snoRNAs which are associated with pseudouridylation. snoRNAs are commonly referred to as guide RNAs but should not be confused with the guide RNAs that direct RNA editing in trypanosomes.

Small nuclear RNA

Small nuclear ribonucleic acid (snRNA) is a class of small RNA molecules that are found within the nucleus of eukaryotic cells. They are transcribed by RNA polymerase II or RNA polymerase III and are involved in a variety of important processes such as RNA splicing (removal of introns from hnRNA), regulation of transcription factors (7SK RNA) or RNA polymerase II (B2 RNA), and maintaining the telomeres. They are always associated with specific proteins, and the complexes are referred to as small nuclear ribonucleoproteins (snRNP) or sometimes as snurps. These elements are rich in uridine content.

Transfer-messenger RNA

Transfer-messenger RNA (abbreviated tmRNA, also known as 10Sa RNA and by its genetic name SsrA) is a bacterial RNA molecule with dual tRNA-like and messenger RNA-like properties. The tmRNA forms a ribonucleoprotein complex (tmRNP) together with Small Protein B (SmpB), Elongation Factor Tu (EF-Tu), and ribosomal protein S1. In trans-translation, tmRNA and its associated proteins bind to bacterial ribosomes which have stalled in the middle of protein biosynthesis, for example when reaching the end of a messenger RNA which has lost its stop codon. The tmRNA is remarkably versatile: it recycles the stalled ribosome, adds a proteolysis-inducing tag to the unfinished polypeptide, and facilitates the degradation of the aberrant messenger RNA. In the majority of bacteria these functions are carried out by standard one-piece tmRNAs. In other bacterial species, a permuted ssrA gene produces a two-piece tmRNA in which two separate RNA chains are joined by base-pairing.

Transfer RNA

Transfer RNA (tRNA) is a small RNA molecule (usually about 74-95 nucleotides) that transfers a specific active amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. It has a 3' terminal site for amino acid attachment. This covalent linkage is catalyzed by an aminoacyl tRNA synthetase. It also contains a three base region called the anticodon that can base pair to the corresponding three base codon region on mRNA. Each type of tRNA molecule can be attached to only one type of amino acid, but because the genetic code contains multiple codons that specify the same amino acid, tRNA molecules bearing different anticodons may also carry the same amino acid.