Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

the ability of the core isolated from Escherichia coli RNA polymerase to interact with specificity-determining subunits isolated from Bacillus subtilis RNA polymerase has been determined by measuring the transcription of "early" and "middle" genes of phage SP82. Two specificity-determining subunits were tested: the sigma subunit and a 28,000 dalton (28 K) peptide isolated from a modified polymerase produced at approximately 8 min after infection of B. subtilis with SP82. Earlier experiments (Spiegelman, G. B. and Whiteley, H. R. (1978) Biochem. Biophys. Res. Commun. 81, 1058-1065) demonstrated that sigma and the 28K peptide are required for the recognition of early and middle gene promoters, respectively, by the B. subtilis core assembly. The present investigation showed that E. coli core interacted more efficiently with the B. subtilis sigma than with the 28K peptide, as judged by the rate of RNA synthesis. Early RNA was produced by the E. coli and B. subtilis holoenzymes and by E. coli core supplenented with B. subtilis sigma and only minor differences were found in comparisons of transcripts by hybridization and by electrophoretic analysis. Measurements of template specificity, the formation of stable enzyme . DNA complexes, and the hybridization of transcripts to fragments of SP82 DNA produced by digestion with restriction endonuclease Hha indicated that E. coli core supplemented with the 28K-supplemented E. coli core with those synthesized by the modified polymerase extracted from B. subtilis 8 min after infection with SP82 suggest that both preparations recognized the same initiation and termination sequences.
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PMID:The interaction of Escherichia coli core RNA polymerase with specificity-determining subunits derived from unmodified and SP82-modified Bacillus subtilis RNA polymerase. 616 Jan 56

The physical map of 2C DNA (cf. following paper in this journal) was compared to the maps of SP01, SP82 and phi e (three other Bacillus subtilis phages containing hydroxymethyluracil in place of thymine in their DNA). The overall organization of the four genomes was remarkably similar, as indicated by the topology of HaeIII and SalI cleavage segments. The proof was gathered for the presence in the four phage DNAs of large redundant ends carrying a single HaeIII recognition site. The location of the latter proved identical for 2C and SP01, but was shifted in the DNAs of SP82 and phi e. Since the redundant end components of these hydroxymethyluracil genomes are colinear, as shown by cross-hybridization studies, the shifting of the HaeIII cleavage site is presumably due to two base substitutions, suppressing an endonuclease recognition site and establishing a new site elsewhere. Relatedness between the genomes of this family of viruses was evaluated from the fraction of conserved restriction fragments. According to these calculations, 6% base substitutions have occurred within the four viral DNAs, in the course of evolution. However, specific segments of 2C DNA were not present in SP01 and phi e DNA, as shown by cross-hybridization with restriction fragments. These data indicate the occurrence of deletions, in addition to base substitutions, as evolutionary mechanisms prevailing in the genomes of this family of phages.
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PMID:Comparison of the physical maps and redundant ends of the chromosomes of phages 2C, SP01, SP82 and phi e. 640 31

We have determined the DNA sequence encoding three sites in Bacillus subtilis phage SP82 early mRNA that are cleaved by a B. subtilis processing endonuclease. The products generated by cleavage of the RNA were sequenced to determine the exact points of RNA strand scission. We propose that the RNA surrounding each processing site forms a stable stem-loop structure and that cleavage occurs at the 5- side of specific adenosine residues located on the loop. The model is consistent with our previous observations that the active site of the enzyme recognizes double-stranded RNA. S1 mapping experiments with RNA-DNA hybrids established that the same cleavage sites are used both in vivo and in vitro. Examination of the B. subtilis processing sites on SP82 mRNA reveals distinctive features of primary and secondary structure that are not present in any of the E. coli RNAase III processing sites previously studied.
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PMID:Bacillus subtilis RNAase III cleavage sites in phage SP82 early mRNA. 640 21

The closely related B. subtilis bacteriophages SPO1 and SP82 have similar introns inserted into a conserved domain of their DNA polymerase genes. These introns encode endonucleases with unique properties. Other intron-encoded "homing" endonucleases cleave both strands of intronless DNA; subsequent repair results in unidirectional gene conversion to the intron-containing allele. In contrast, the enzymes described here cleave one strand on both intron-containing and intronless targets at different distances from their common intron insertion site. Most surprisingly, each enzyme prefers DNA of the heterologous phage. The SP82-encoded endonuclease is responsible for exclusion of the SPO1 intron and flanking genetic markers from the progeny of mixed infections, a novel selective advantage imparted by an intron to the genome in which it resides.
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PMID:Beyond homing: competition between intron endonucleases confers a selective advantage on flanking genetic markers. 856 67

Here we describe the discovery of a group I intron in the DNA polymerase gene of Bacillus thuringiensis phage Bastille. Although the intron insertion site is identical to that of the Bacillus subtilis phages SPO1 and SP82 introns, the Bastille intron differs from them substantially in primary and secondary structure. Like the SPO1 and SP82 introns, the Bastille intron encodes a nicking DNA endonuclease of the H-N-H family, I-BasI, with a cleavage site identical to that of the SPO1-encoded enzyme I-HmuI. Unlike I-HmuI, which nicks both intron-minus and intron-plus DNA, I-BasI cleaves only intron-minus alleles, which is a characteristic of typical homing endonucleases. Interestingly, the C-terminal portions of these H-N-H phage endonucleases contain a conserved sequence motif, the intron-encoded endonuclease repeat motif (IENR1) that also has been found in endonucleases of the GIY-YIG family, and which likely comprises a small DNA-binding module with a globular betabetaalphaalphabeta fold, suggestive of module shuffling between different homing endonuclease families.
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PMID:The nicking homing endonuclease I-BasI is encoded by a group I intron in the DNA polymerase gene of the Bacillus thuringiensis phage Bastille. 1279 34

Many group I introns encode endonucleases that promote intron homing by initiating a double-stranded break-mediated homologous recombination event. In this work we describe intron homing in Bacillus subtilis phages SPO1 and SP82. The introns encode the DNA endonucleases I-HmuI and I-HmuII, respectively, which belong to the H-N-H endonuclease family and possess nicking activity in vitro. Coinfections of B. subtilis with intron-minus and intron-plus phages indicate that I-HmuI and I-HmuII are required for homing of the SPO1 and SP82 introns, respectively. The homing process is a gene conversion event that does not require the major B. subtilis recombination pathways, suggesting that the necessary functions are provided by phage-encoded factors. Our results provide the first examples of H-N-H endonuclease-mediated intron homing and the first demonstration of intron homing initiated by a nicking endonuclease.
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PMID:Group I intron homing in Bacillus phages SPO1 and SP82: a gene conversion event initiated by a nicking homing endonuclease. 1520 33