rRNA 2'-O-methyltransferase fibrillarin is an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
that in humans is encoded by the ''FBL''
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 b ...
.
Function
This gene product is a component of a nucleolar small nuclear ribonucleoprotein (snRNP) particle thought to participate in the first step in processing pre-ribosomal (r)RNA. It is associated with the
U3,
U8, and
U13 small nucleolar RNAs and is located in the dense fibrillar component (DFC) of the
nucleolus. The encoded protein contains an N-terminal repetitive domain that is rich in glycine and arginine residues, like fibrillarins in other species. Its central region resembles an RNA-binding domain and contains an RNP consensus sequence. Antisera from approximately 8% of humans with the autoimmune disease
scleroderma recognize fibrillarin.
Fibrillarin is a component of several ribonucleoproteins including a nucleolar small nuclear ribonucleoprotein (
SnRNP) and one of the two classes of
small nucleolar ribonucleoproteins (snoRNPs). SnRNAs function in
RNA splicing while snoRNPs function in
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 ...
processing.
Fibrillarin is associated with U3, U8 and U13
small nuclear RNAs in mammals and is similar to the yeast NOP1 protein. Fibrillarin has a well conserved sequence of around 320 amino acids, and contains 3 domains, an N-terminal Gly/Arg-rich region; a central domain resembling other RNA-binding proteins and containing an RNP-2-like consensus sequence; and a C-terminal alpha-helical domain. An evolutionarily related pre-rRNA processing protein, which lacks the Gly/Arg-rich domain, has been found in various archaea.
A study by Schultz et al. indicated that the K-turn binding 15.5-kDa protein (called Snu13 in yeast) interacts with
spliceosome proteins hPRP31, hPRP3, hPRP4, CYPH and the small nucleolar ribonucleoproteins
NOP56,
NOP58, and fibrillarin. The 15.5-kDa protein has sequence similarity to other RNA-binding proteins such as ribosomal proteins S12, L7a, and L30 and the snoRNP protein
NHP2. The U4/U6 snRNP contains 15.5-kDa protein. The 15.5-kDa protein also exists in a ribonucleoprotein complex that binds the U3 box B/C motif. The 15.5-kDa protein also exists as one of the four core proteins of the
C/D small nucleolar ribonucleoprotein that mediates methylation of pre-ribosomal RNAs.
Structural evidence supporting the idea that fibrillarin is the snoRNA
methyltransferase has been reviewed.
The structure and function of small nucleolar ribonucleoproteins
by Steve L. Reichow, Tomoko Hamma, Adrian R. Ferré-D'Amaré and Gabriele Varani in '' Nucleic Acids Research'' (2007) Volume 35, pages 1452–1464.
Interactions
Fibrillarin has been shown to interact with DDX5 and SMN1.
References
Further reading
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{{PDB Gallery, geneid=2091
Molecular biology