| Abstract
| - Flbrillarin is a nucleolar protein which is associated with small nucleolar RNAs, and is required for pre-rRNA processing. We have cloned and characterized the gene encoding flbrillarin in the fission yeast Schlzosaccharomyces pombe and we have followed Its expression under various conditions. Fission yeast flbrillarin is a 305 amino-acld protein which appears to be highly conserved throughout evolution. In Xenopus, human or Saccharomyces cerevlslae, a single flbrillarin mRNA is detected while, in S.pombe a single copy gene encodes different mRNAs which differ at the 3′ ends. Under normal growth conditions, two mRNAs of 1.1 and 1.35 kb are detected with the 1.1 kb being the most abundant. Both the total amount and relative abundance of these two mRNAs are strongly affected by exposure to low temperature, namely the 1.1 kb mRNA almost disappears while the 1.35 kb is less markedly diminished. A new species of 3.2 kb accumulates in the cell, which contains an unusually long 3′ untranslated region of 2 kb. We have found that exposure of the cells to a cold shock has a profound effect on 3′ end formation in S.pombe since the transcription of several other mRNAs is also capable of skipping the normal 3′ end site to terminate at a further downstream site.
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