Small Cajal body-specific RNAs (scaRNAs) are a class of
small nucleolar RNAs (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 (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as Organ (anatomy), organs are to th ...
(cellular sub-organelle) involved in the biogenesis of
small nuclear ribonucleoproteins (snRNPs or snurps). ScaRNAs guide the modification (
methylation
Methylation, in the chemistry, chemical sciences, is the addition of a methyl group on a substrate (chemistry), substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replac ...
and
pseudouridylation) of
RNA polymerase II
RNA polymerase II (RNAP II and Pol II) is a Protein complex, multiprotein complex that Transcription (biology), transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNA pol ...
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 (; : nucleoli ) is the largest structure in the cell nucleus, nucleus of eukaryote, eukaryotic cell (biology), cells. It is best known as the site of ribosome biogenesis. The nucleolus also participates in the formation of signa ...
.
''Drosophila'' scaRNAs
Several studies identified scaRNAs in ''
Drosophila
''Drosophila'' (), from Ancient Greek δρόσος (''drósos''), meaning "dew", and φίλος (''phílos''), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or p ...
.''
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
In
molecular biology
Molecular biology is a branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, biomolecular synthesis, modification, mechanisms, and interactio ...
, 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
A non-coding RNA (ncRNA) is a functional RNA molecule that is not Translation (genetics), translated into a protein. The DNA sequence from which a functional non-coding RNA is transcribed is often called an RNA gene. Abundant and functionally imp ...
, which are functional products of
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
s not
translated into
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
s. Such RNA molecules usually contain important
secondary structure
Protein secondary structure is the local spatial conformation of the polypeptide backbone excluding the side chains. 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