Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mating-type switching in fission yeast depends on an imprint at the mat1 locus. Previous data showed that the imprint is made in the DNA strand replicated as lagging. We now identify this imprint as an RNase-sensitive modification and suggest that it consists of one or two RNA residues incorporated into the mat1 DNA. Formation of the imprint requires swi1- and swi3-dependent pausing of the replication fork. Interestingly, swi1 and swi3 mutations that abolish pausing do not affect the use of lagging-strand priming site during replication. We show that the pausing of replication and subsequent formation of the imprint occur after the leading-strand replication complex has passed the site of the imprint and after lagging-strand synthesis has initiated at this proximal priming site. We propose a model in which a swi1- and swi3-dependent signal during lagging-strand synthesis leads to pausing of leading-strand replication and the introduction of the imprint.
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PMID:RNase-sensitive DNA modification(s) initiates S. pombe mating-type switching. 1505 61

The sexual locus mat1, in the fission yeast Schizosaccharomyces pombe, efficiently switches between the two mating types, P and M, by a process similar to gene conversion, using the silent mat2-P and mat3-M loci, respectively, as donors of the P and M genetic information . It has been proposed that an asymmetrically inherited, site- and strand-specific imprint at mat1 initiates the mating-type switching process . The molecular nature of the imprint is controversial; it was initially described as a double-strand break and then as a single-strand lesion or a strand-specific, alkali-labile modification . Here, we use E. coli DNA ligase in vitro to demonstrate that the imprint is a nick with no resection of nucleotides. By using ligation-mediated PCR, we show that the nick contains 3'OH and 5'OH unphosphorylated termini resistant to RNase treatments. This nonmutational mark on one of the DNA strands provides the first example of a novel type of imprint.
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PMID:A programmed strand-specific and modified nick in S. pombe constitutes a novel type of chromosomal imprint. 1588 85