MOLECULAR-CLONING AND SEQUENCE-ANALYSIS OF U3 SNORNA-ASSOCIATED MOUSEFIBRILLARIN

We have isolated and determined the sequence of a 1.1-kb cDNA from a m urine WEHI-3 macrophage library which encodes the highly conserved, nu cleolar protein, fibrillarin. The murine fibrillarin protein sequence displays 94.2% identity with human fibrillarin, 82.9% identity with am phibian fibrillarin and 74.0% identity with the yeast fibrillarin homo log, NOP1. Immunoprecipitation showed that anti-fibrillarin autoantibo dies from human scleroderma sera and the monoclonal autoantibody 72B9 recognize the approx. 34-36 kDa in vitro transcribed and translated pr otein. Mouse fibrillarin contains a N-terminal glycine- and arginine-r ich (GAR) domain which although conserved among the fibrillarins is no t as strongly conserved as several regions in the carboxy tail of the protein. Specific amino acid residues in yeast NOP1 thought to be asso ciated with the synthesis and maturation of ribosomes show strong cons ervation between the mouse, human. amphibian and yeast protein sequenc es.