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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

45S ribosomal precursor RNA and large heterogeneous RNA molecules (greater than 45S) extracted from human leukemic cells were incubated in vitro with purified RNase III, which specifically attacks double-helical RNA regions. About 50% of the ribosomal precursor was cleaved into two major fragments sedimenting at 28S and 32S respectively. A limited number of cleavages was also introduced in about 40% of heterogeneous RNA molecules sedimenting faster than 45S, causing a partial 'shift' to a polydisperse distribution in the 10S-45S range.
Mol Biol Rep 1977 Dec
PMID:In vitrocleavage of 45S pre-ribosomal RNA and of giant heterogeneous RNA extracted from human leukemic cells. 59 70

1. New high molecular weight RNA species have been found in an RNase III deficient mutant of E. coli. These RNA's were very minor but stable components of the cells, and their molecular weights, which range from 3-5.5 million daltons, are higher than that of 30S precursor ribosomal RNA. In these respects these RNAs are similar to the 2.5 M RNA reported previously (Yuki and Wittmann, 1974). 2. A method to analyse minor RNA components is described. A linear relationship between logarithms of molecular weights and logarithms of distance moved in 1.5-7.5% polyacrylamide concentration gradient gels is also described in this report. 3. DNA species whose molecular weights ranged from 1.8 to 5.5 million daltons and also a species of 8 million daltons are described. two techniques commonly used to identify RNA, viz. DNase treatment and labeling with radioactive uridine, are discussed in connection with these DNAs. 4. The determination of the molecular weight of 30S precursor ribosomal RNA is discussed and it is suggested that this RNA is heterogenous, consisting of two species of molecular weight 1.8 million daltons and 2.0 million daltons, respectively.
Mol Gen Genet 1976 Mar 22
PMID:Detection of ribonucleic acids which are larger than 30S precursor ribosomal RNA in RNase III deficient E. coli cells. 77 88

An isogenic pair of Escherichia coli strains, one carrying an rnc+ and the other an rnc- allele (a mutation which reduces the level of ribonuclease III), was compared. The rnc- strain fails to grow at very elevated temperatures (for E. coli) while the rnc+ strain does grow exponentially. Assaying the residual RNase III like activity in extracts of the rnc- strain at different pHs and at different temperatures suggested that this residual RNase III like activity is not due to RNase III. This raised the possibility that the rnc- strain is devoid of any RNase III activity in the cell. Comparing the decay of newly synthesized RNA and functional decay of beta-galactosidase mRNA in such strains revealed that in both strains these parameters proceed in similar rates, which suggests that RNase III is not involved in the metabolism of mRNA. During carbon starvation preexisting total RNA, as well as 23S and 16S rRNA, decay faster in the rnc- strain, thus eliminating the possibility that RNase III is the endoribonuclease which initiates the decay of rRNA during starvation (Kaplan and Apirion, 1975a).
Mol Gen Genet 1976 Mar 22
PMID:Consequences of losing ribonuclease III on the Escherichia coli cell. 77 91

"SPACER" SEQUENCES OF AN RRNA gene transcript were detected with high efficiency by hybridization with DNA of the specilized transducing phase phi80rrn. Hybridization-competition studies revealed that 20 to 23% of the 30S precursor rRNA, obtained from E. coli mutant strain AB301/105, consist of "spacer" sequences. The "spacer" sequences formed hybrids with E. coli DNA, but not with Vibrio DNA. Experiments with RNA labeling in the presence of rifampicin showed that more than 80% of the spacer sequences arrive in full-length 30S pre rRNA chains before any cleavage of the RNA occurs. The hybridization assays also permitted the detection of "spacer" sequences in pulse-labeled rRNA of wild-type cells, in which the 30S pre-rRNA is already cleaved during its synthesis. Many of these "spacer" sequences degraded to alcohol-soluble materials with a half-life time of 1.2 min. The half-life was not lengthened by the treatment of cells with chloramphenicol, which stabilizes bulk mRNA. However, unstable "spacer" sequences transcribed in cells deficient in RNase III exhibited slower degradation, with a half-life time of about 9 min, whereas the cleavage of 30S pre-rRNA to smaller RNA species occurred with a half-life of about 3 min. These results are consistent with the notion that a rate-limiting action of RNase III in the initial attack leads to degradation of "spacer" sequences in rRNA gene transcript; and that degradation is not at all connected with ribosome translocation.
Mol Gen Genet 1976 Aug 02
PMID:Stability of "spacer" sequences of pre-ribosomal RNA in Escherichia coli. 79 93

E. coli strains carrying the rnc-105 allele do not show any level of RNase III in extracts, grow slower than rnc+ strains at temperatures up to 45 degrees C and fail to grow at 45 degrees C. Revertants which can grow at 45 degrees C were isolated. The vast majority of them still do not grow as fast as rnc+ strains and did not regain RNase III activity. The mutation(s) which caused them are suppressor mutations (physiological suppressors) which do not map in the immediate vicinity of the rnc gene. A few of the revertants regain normal growth, and contain normal levels of RNase III. They do not harbor the rnc-105 allele and therefore are considered to be true revertants. By using purines other than adenine it was possible to isolate rnc + pur- revertants from an rnc- pur- strain with relative ease. They behaved exactly like the true rnd+ revertants isolated from rns- strains at 45 degrees C. A merodiploid strain which contains the rnc+ gene on an episome behaves exactly like an rnc+ strain with respect to growth and RNA metabolis, eventhough its specific RNase III activity is about 60% of that of an rnc+ strain; thus the level of RNase III is not limiting in the cell. The rnc- strains show a characteristic pattern of transitory molecules, related to rRNA, 30S, 25S, "p23" and 18S, which are not observed in rnc+ strains. This pattern is unchanged in rnc- strains and in the revertants which are still lacking RNase III, regardless of the temperature in which RNA synthesis was examined (30 degrees to 45 degrees C). On the other hand, in the rnc+ strains as well as in the true revertants and the rnc+/rnc- merodiploid, the normal pattern of p16 and p23 is observed at all temperatures. These findings suggest that all the effects observed in RNase III- strains are due to pleiotropic effects of the rnc-105 allele, and that the enzyme RNase III is not essential for the viability of the E. coli cell.
Mol Gen Genet 1976 Dec 08
PMID:Revertants from RNase III negative strains of Escherichia coli. 79 80

The hok/sok, srnB and pnd systems of plasmids R1, F and R438 mediate plasmid maintenance by killing plasmid-free segregants. The systems encode exceptionally stable full-length mRNAs that code for potent cell toxins that kill the cells from within. The systems also produce truncated mRNAs whose appearance is correlated with killing activity. The truncated mRNAs are shortened by 35 to 70 nucleotides in the 3' ends, but have the same 5' ends as the full-length transcripts. Translation of the stable killer mRNAs is regulated by unstable antisense RNAs that are complementary to the leader regions of the full-length and truncated mRNAs. We show here, that both the presence of the antisense RNA and of the host enzyme RNase III is required for rapid cleavage of the truncated mRNAs, and we map the cleavage point in the Hok mRNA in vitro and in vivo to be located between nucleotides +245 and +246. The RNase III cleavage products of the Hok mRNA were found to be very unstable in vivo. Thus, RNase III cleavage seems to be the initial event leading to decay of the killer mRNAs. In an rnc- strain, the truncated mRNA species were found in steady-state cells. This observation indicates that the truncated mRNAs are formed constitutively and independently of the presence of the antisense RNAs. Thus, the antisense RNAs prevent the accumulation of the truncated mRNAs solely by mediating their rapid hydrolysis by RNase III. Furthermore, the generation of the truncated killer mRNAs in the rnc- host indicate that RNase III is dispensable for induction of the killer gene systems. Based on these and on observations obtained previously, we present a molecular model that explains the activation of the killer mRNAs in plasmid-free segregants and after addition of rifampicin.
J Mol Biol 1992 Aug 05
PMID:Mechanism of killer gene activation. Antisense RNA-dependent RNase III cleavage ensures rapid turn-over of the stable hok, srnB and pndA effector messenger RNAs. 138 May 62

We have established that the long non-coding intercistronic region of the dicB operon of Escherichia coli expresses a trans-acting division inhibitor specified by a region dicF, at most 65 nucleotides-long. The present study deals with the processing of dicBF operon mRNA in vivo, and identifies the dicF gene product as a 53 nucleotide RNA species. A sequence at the end of DicF resembles, and behaves as, a Rho-independent terminator, but further processing of readthrough transcripts, presumably by RNase III, followed by a limited 3' to 5' degradation, appears to generate additional DicF-RNA 3' ends. For the 5' end of DicF-RNA, our results show that a 190 nucleotide precursor DicF-RNA species is formed by cleavage at an RNase III site, while the 53 nucleotide minimal DicF-RNA is generated by further processing requiring the presence of an active form of RNase E in vivo. These data indicate that an untranslated product derived from an operon RNA can have a regulatory activity by affecting cell division.
J Mol Biol 1990 Apr 05
PMID:Escherichia coli cell division inhibitor DicF-RNA of the dicB operon. Evidence for its generation in vivo by transcription termination and by RNase III and RNase E-dependent processing. 169 Dec 99

The transcripts of the rpsO-pnp operon of Escherichia coli, coding for ribosomal protein S15 and polynucleotide phosphorylase, are processed at four sites in the 249 nucleotides of the intercistronic region. The initial processing step in the decay of the pnp mRNA is made by RNase III, which cuts at two sites upstream from the pnp gene. The other two cleavages are dependent on the wild-type allele of the rne gene, which encodes the endonucleolytic enzyme RNase E. The cuts are made 37 nucleotides apart at the base of the stem-loop structure of the rho-independent attenuator located downstream from rpsO. The cleavage downstream from the attenuator generates an rpsO mRNA.nearly identical with the monocistronic attenuated transcript, while the cleavage upstream from the transcription attenuator gives rise to an rpsO mesage lacking the terminal 3' hairpin structure. The rapid degradation of the processed mRNA in an rne+ strain, compared to the slow degradation of the transcript that accumulates in an rne- strain, suggests that RNase E initiates the decay of the rpsO message by removing the stabilizing stem-loop at the 3' end of the RNA.
J Mol Biol 1991 Jan 20
PMID:Decay of mRNA encoding ribosomal protein S15 of Escherichia coli is initiated by an RNase E-dependent endonucleolytic cleavage that removes the 3' stabilizing stem and loop structure. 170 67

Cells overexpressing the RNA-processing enzymes RNase III, RNase E and RNase P were fractionated into membrane and cytoplasm. The RNA-processing enzymes were associated with the membrane fraction. The membrane was further separated to inner and outer membrane and the three RNA-processing enzymes were found in the inner membrane fraction. By assaying for these enzymatic activities we showed that even in a normal wild-type strain of Escherichia coli these enzymes fractionate primarily with the membrane. The RNA part of RNase P is found in the cytosolic fraction of cells overexpressing this RNA, while the overexpressed RNase P protein sediments with the membrane fraction; this suggests that the RNase P protein anchors the RNA catalytic moiety of the enzyme to a larger entity. The implications of these findings for the cellular organization of the RNA-processing enzymes in the cell are discussed.
Mol Microbiol 1991 Jul
PMID:Location of the RNA-processing enzymes RNase III, RNase E and RNase P in the Escherichia coli cell. 194 11

Using lambda phage clones containing segments of the Escherichia coli K12 chromosome as hybridization probes, we found one gene at 42 min on the E. coli chromosome map, the expression of which was affected by RNase III. The sequence of the DNA fragment containing this gene (gen-165) revealed the presence of an open reading frame encoding a polypeptide of 165 amino acid residues. The amino acid sequence deduced from the nucleotide sequence exhibited a remarkable similarity to that of the human ferritin H chain.
Mol Gen Genet 1991 Mar
PMID:Cloning and sequencing of an Escherichia coli K12 gene which encodes a polypeptide having similarity to the human ferritin H subunit. 201 45


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