FBL
FBL (fibrillarin rRNA 2'-O-methyltransferase, also known as fibrillarin, FIB, FLRN, RNU3IP1 and Nop1) is an S-adenosyl-L-methionine-dependent methyltransferase of the nucleolus. It methylates both RNA and protein substrates and contributes to pre-rRNA processing. Browse Assay Genie's current range of FBL research reagents below, or read on for the biology behind the target.
FBL is an S-adenosyl-L-methionine-dependent methyltransferase that can methylate both RNAs and proteins. In pre-rRNA processing it catalyses site-specific 2'-hydroxyl methylation of ribose moieties in pre-ribosomal RNA. Site specificity comes from a guide RNA that base pairs with the substrate, and methylation occurs at a characteristic distance from the sequence involved in that base pairing. FBL is also thought to catalyse 2'-O-methylation of U6 snRNAs in box C/D RNP complexes, a modification required for mRNA splicing fidelity.
As a protein methyltransferase, FBL methylates Gln-105 of histone H2A (H2AQ104me). This mark impairs binding of the FACT complex and is specifically present at the 35S ribosomal DNA locus. FBL is also part of the small subunit (SSU) processome, the first precursor of the small eukaryotic ribosomal subunit. During SSU processome assembly in the nucleolus, ribosome biogenesis factors, an RNA chaperone and ribosomal proteins associate with the nascent pre-rRNA. Together they generate RNA folding, modification, rearrangement and cleavage, and the RNA exosome targets pre-ribosomal RNA for degradation.
The FBL gene product is a component of a nucleolar small nuclear ribonucleoprotein (snRNP) particle associated with the U3, U8 and U13 small nuclear RNAs. It is located in the dense fibrillar component of the nucleolus, and is also found in the nucleoplasm. The protein has an N-terminal repetitive domain rich in glycine and arginine, as in fibrillarins from other species, and a central region resembling an RNA-binding domain with an RNP consensus sequence. It belongs to the methyltransferase superfamily, fibrillarin family. Antisera from about 8% of people with the autoimmune disease scleroderma recognise fibrillarin.
FBL takes part in pre-rRNA processing and is part of the SSU processome that assembles the small ribosomal subunit in the nucleolus.
FBL catalyses guide RNA-directed 2'-O-methylation of ribose in pre-rRNA and probably of U6 snRNA within box C/D RNP complexes.
FBL methylates histone H2A at Gln-105, a mark that impairs FACT complex binding and is present at the 35S ribosomal DNA locus.
Antisera from approximately 8% of people with scleroderma recognise fibrillarin, making FBL a recognised nucleolar autoantigen.
FBL is an S-adenosyl-L-methionine-dependent methyltransferase. It methylates ribose 2'-hydroxyl groups in pre-rRNA, guided by base-pairing RNAs, and methylates histone H2A at Gln-105. It is part of the SSU processome in the nucleolus. Check the datasheet of any product for its validated reactivity.
FBL is also called fibrillarin, FIB, FLRN, RNU3IP1 and Nop1. The HGNC name is fibrillarin rRNA 2'-O-methyltransferase, and UniProt lists it as rRNA 2'-O-methyltransferase fibrillarin. HGNC places it in the U3 small nucleolar ribonucleoprotein gene group.
Mouse and rat both have an Fbl ortholog, and the NCBI summary notes that the glycine- and arginine-rich N-terminal domain is shared with fibrillarins in other species. Antisera from about 8% of people with scleroderma recognise fibrillarin.
Other targets with similarly spelled gene symbols, listed for navigation; they are not functional partners of FBL.
Gene and protein annotations from HGNC, NCBI Gene and UniProt P22087; product specifications from Assay Genie datasheets.