uvi15(+) is induced by various stresses including exposure to UV-light. Previously, we demonstrated that the UV-induction is mainly regulated at the post-transcriptional level through a cis-acting element in the pre-mRNA. Here we show that deletion analyses define an 18-nt element responsible for the UV-induction. RNA gel mobility shift assay showed that a specific protein(s) could form a complex with the 54-nt element but its binding ability is moderately decreased in response to UV-light. Using yeast three-hybrid screen, we isolated a homolog of fibrillarin as a protein interacting with the 54-nt element, which is a key nucleolar protein for pre-rRNA processing. We further showed that the recombinant fibrillarin specifically binds to the element in a sequence-specific manner. Thus, the data suggest that fission yeast fibrillarin might regulate uvi15(+) mRNA stability via binding with the 54-nt element in the pre-mRNA, implying that fibrillarin is involved in both pre-mRNA and pre-rRNA processing. (C) 2002 Elsevier Science (USA). All rights reserved.