Small Cajal body-specific RNAs (scaRNAs) are a class of

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 ...

s (snoRNAs) that specifically localise to the Cajal body, a

nuclear Nuclear may refer to: Physics Relating to the nucleus of the atom: * Nuclear engineering *Nuclear physics *Nuclear power *Nuclear reactor *Nuclear weapon *Nuclear medicine *Radiation therapy *Nuclear warfare Mathematics *Nuclear space *Nuclear ...

organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' the ...

(cellular sub-organelle) involved in the biogenesis of small nuclear ribonucleoproteins (snRNPs or snurps). ScaRNAs guide the modification (

methylation In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...

and

pseudouridylation Pseudouridine (abbreviated by the Greek letter psi- Ψ) is an isomer of the nucleoside uridine in which the uracil is attached via a carbon-carbon instead of a nitrogen-carbon glycosidic bond. (In this configuration, uracil is sometimes referred ...

) of

RNA polymerase II RNA polymerase II (RNAP II and Pol II) is a multiprotein complex that transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNAP enzymes found in the nucleus of eukaryoti ...

transcribed spliceosomal RNAs U1, U2, U4, U5 and U12. The first scaRNA identified was U85. It is unlike typical snoRNAs in that it is a composite C/D box and H/ACA box snoRNAs and can guide both pseudouridylation and 2′-''O''-methylation. Not all scaRNAs are composite C/D and H/ACA box snoRNA and most scaRNAs are structurally and functionally indistinguishable from snoRNAs, directing

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 ribosomal ...

(rRNA) modification in the

nucleolus The nucleolus (, plural: nucleoli ) is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis, which is the synthesis of ribosomes. The nucleolus also participates in the formation of sig ...

''Drosophila'' scaRNAs

Several studies identified scaRNAs in ''

Drosophila ''Drosophila'' () is a genus of flies, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species ...

.'' One of the studies showed that several ''Drosophila'' scaRNAs could function equally well in the nucleoplasm of mutant flies that lack Cajal bodies. Further investigation showed that scaRNA pugU6-40 targets U6 snRNA, whose modification occurs in the nucleolus not CB and that pugU1-6 and pug U2-55 guide 2 RNAs: snRNA and 28s rRNA.

Small Cajal body-specific RNA 1

molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physi ...

, Small Cajal body-specific RNA 1 (also known as SCARNA1 or ACA35) is a small nucleolar RNA found in Cajal bodies and believed to be involved in the pseudouridylation of U2 spliceosomal RNA at residue U89. scaRNA1 is a non-coding RNA, which are functional products of

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

s not

translated Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...

into

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

s. Such RNA molecules usually contain important

secondary structure Protein secondary structure is the three dimensional conformational isomerism, form of ''local segments'' of proteins. The two most common Protein structure#Secondary structure, secondary structural elements are alpha helix, alpha helices and beta ...

or ligand- binding motifs and are involved in many important biological processes in the cell. scaRNA1 belongs to the H/ACA box class of snoRNAs, as it has the predicted hairpin-hinge-hairpin-tail structure, conserved H/ACA-box motifs, and is found associated with GAR1 protein.

References

External links

snoRNAbase: human H/ACA and C/D box snoRNA database
* Non-coding RNA Small nuclear RNA Spliceosome RNA splicing {{genetics-stub