Fibrillarin is a 2'-O-methyltransferase located in fibrillar regions and Cajal bodies of the nucleolus, where RNA transcription and pre-RNA processing take place (1,2). Fibrillarin associates with several other structual proteins as well as box C/D snoRNA to form a complex that functions in pre-rRNA processing, pre-rRNA methylation and ribosome assembly. This complex catalyzes site-specific 2'-O-ribose methylation of targeted nucleotides within the rRNA sequence (3,4). The sequence, structure and function of fibrillarin are highly conserved and fibrillarin gene expression is essential for early embryonic development (5).
