Fibrillarin is a highly conserved component of a nucleolar small ribonucleoprotein (SnRNP) complex in mammals, involved in the processing of ribosomal RNA during ribosomal biogenesis (1). The molecule runs at about 35kDa on SDS-PAGE, and the N terminal ~80 amino acids contain multiple copies based on the peptide RGG, or arginine-glycine-glycine, sometimes referred to as GAR repeats, characteristic of the GAR family of molecules. The remaining ~240 amino acids consist of the so called fibrillarin domain (1,2). Human fibrillarin has been characterized (accession P22087)
and the human fibrillarin gene is located on chromosome 19 (19q13.1)
. Autoantibodies to fibrillarin are seen in the blood of scleroderma patients (2). The yeast homologue of human fibrillarin is Nop1p (3). Recent studies show that knock out of the fibrillarin gene in mice results in embryonic lethality, although mice with only one functional fibrillarin/Nop1p gene were viable (4). Our antibody was made against a recombinant protein expressed in bacteria and is identical to the human sequence. The antibody is an excellent marker of nucleoli. The HGNC
name for this protein is FBL
1. Aris JP and Blobel G. cDNA cloning and sequencing of human fibrillarin, a conserved nucleolar protein recognized by autoimmune antisera. Proc. Natl. Acad. Sci. 88:931-935 (1991).
2. Ochs RL, Lischwe MA, Spohn WH, Busch H. Fibrillarin: a new protein of the nucleolus identified by autoimmune sera. Biol Cell 54:123-133 (1985).
3. Aris JP and Blobel G. Identification and characterization of a yeast nucleolar protein that is similar to a rat liver nucleolar protein. J. Cell Biol. 107:17-31 (1988).
4. Newton K, Petfalski E, Tollervey D, Caceres JF. Fibrillarin is essential for early development and required for accumulation of an intron-encoded small nucleolar RNA in the mouse. Mol Cell Biol. 23:8519-8527 (2003).