Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.3 (RNase III)
 1,015 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Core snRNP proteins bind snRNA through the conserved Sm site, PuA(U)n>/=3GPu. While yeast U1 snRNA has three matches to the Sm consensus, the U1 3'-terminal Sm site was found to be both necessary and sufficient for U1 function. Mutation of this site inhibited pre-mRNA splicing, blocked cell division and resulted in the accumulation of two 3'-extended forms of the U1 snRNA. Cells which harbor the Sm site mutation lack mature U1 RNA (U1alpha) but have a minor polyadenylated species, U1gamma, and a prominent, non-polyadenylated species, U1beta. Metabolic depletion of the essential Sm core protein, Smd1p, also resulted in the increased accumulation of U1beta and U1gamma. In vitro, synthetic U1 precursors were cleaved by Rnt1p (RNase III) very near the U1beta 3'-end observed in vivo. We propose that U1beta is an Rnt1p-cleaved intermediate and that U1 maturation to the U1alpha form occurs through an Sm-sensitive step. Interestingly, both U1alpha and a second, much longer RNA, U1straightepsilon, were produced in an rnt1 mutant strain. These results suggest that yeast U1 snRNA processing may progress through Rnt1p-dependent and Rnt1p-independent pathways, both of which require a fun-ctional Sm site for final snRNA maturation.
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PMID:U1 snRNA is cleaved by RNase III and processed through an Sm site-dependent pathway. 986 84

Genome-binding proteins with scaffolding and/or regulatory functions are common in living organisms and include histones in eukaryotic cells, histone-like proteins in some double-stranded DNA (dsDNA) viruses, and the nucleocapsid proteins of single-stranded RNA viruses. dsRNA viruses nevertheless lack these ribonucleoprotein (RNP) complexes and are characterized by sharing an icosahedral T=2 core involved in the metabolism and insulation of the dsRNA genome. The birnaviruses, with a bipartite dsRNA genome, constitute a well-established exception and have a single-shelled T=13 capsid only. Moreover, as in many negative single-stranded RNA viruses, the genomic dsRNA is bound to a nucleocapsid protein (VP3) and the RNA-dependent RNA polymerase (VPg). We used electron microscopy and functional analysis to characterize these RNP complexes of infectious bursal disease virus, the best characterized member of the Birnaviridae family. Mild disruption of viral particles revealed that VP3, the most abundant core protein, present at approximately 450 copies per virion, is found in filamentous material tightly associated with the dsRNA. We developed a method to purify RNP and VPg-dsRNA complexes. Analysis of these complexes showed that they are linear molecules containing a constant amount of protein. Sensitivity assays to nucleases indicated that VP3 renders the genomic dsRNA less accessible for RNase III without introducing genome compaction. Additionally, we found that these RNP complexes are functionally competent for RNA synthesis in a capsid-independent manner, in contrast to most dsRNA viruses.
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PMID:Infectious Bursal disease virus: ribonucleoprotein complexes of a double-stranded RNA virus. 1906