FBL

This gene product is a component of a nucleolar small nuclear ribonucleoprotein (snRNP) particle thought to participate in the first step in processing preribosomal RNA. It is associated with the U3, U8, and U13 small nuclear 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. [provided by RefSeq, Jul 2008]

Fibrillarin

S-adenosyl-L-methionine-dependent methyltransferase that has the ability to methylate both RNAs and proteins (PubMed:24352239, PubMed:30540930, PubMed:32017898).

Involved in pre-rRNA processing by catalyzing the site-specific 2'-hydroxyl methylation of ribose moieties in pre-ribosomal RNA (PubMed:30540930).

Site specificity is provided by a guide RNA that base pairs with the substrate (By similarity).

Methylation occurs at a characteristic distance from the sequence involved in base pairing with the guide RNA (By similarity).

Probably catalyzes 2'-O-methylation of U6 snRNAs in box C/D RNP complexes (PubMed:32017898).

U6 snRNA 2'-O-methylation is required for mRNA splicing fidelity (PubMed:32017898).

Also acts as a protein methyltransferase by mediating methylation of 'Gln-105' of histone H2A (H2AQ104me), a modification that impairs binding of the FACT complex and is specifically present at 35S ribosomal DNA locus (PubMed:24352239, PubMed:30540930).

Box C/D RNA 3'-end processing Source: GO_Central
Histone glutamine methylation Source: UniProtKB
Osteoblast differentiation Source: UniProtKB
rRNA methylation Source: UniProtKB
rRNA processing Source: ProtInc
SnoRNA localization Source: UniProtKB

Nucleolus; Nucleoplasm. Fibrillar region of the nucleolus.

Ubiquitinated. Ubiquitination leads to proteasomal degradation (PubMed:19208757). Deubiquitinated by USP36 (PubMed:19208757).
By homology to other fibrillarins, some or all of the N-terminal domain arginines are modified to asymmetric dimethylarginine (DMA).By similarity
Acetylated by CREBBP/CBP, preventing methylation of 'Gln-105' of histone H2A (H2AQ104me), without affecting rRNA methylation (PubMed:30540930). Deacetylation by SIRT7 restores methylation of 'Gln-105' of histone H2A (H2AQ104me) (PubMed:30540930).