Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated three aspects of RNA turmor virus replication and cell transformation: (1) the properties of the purified avian and mammalian viral RNA-directed DNA polumerase, (2) some characteristics of the viral 60-70S RNA genome, 30-40S RNA subunits and intracellular viral RNA species, and (3) the interaction of the viral DNA polymerase with its RNA template early during infection and cell transformation by the murine sarcoma-leukemia virus (MSV[MLV]). Avian myeloblastosis virus (AMV) contains two forms of RNA-directed DNA polymerase, alpha, consisting of a single polypeptide of molecular weight 65,000, and alphabeta, consisting of two polypeptides of molecular weights 65,000 and 105,000. The alpha and alphabeta forms of AMV DNA polymerase both possess RNase H activity that requires free end termini on the ribopolymer and can degrade the RNA of the RNA-DNA hybrid in the 3' to 5' and 5' to 3' directions. But, alpha and alphabeta possess a different mode of exoribonuclease activity. While alphabeta RNase H is a processive exoribonuclease that degrades the polynucleotide chain to a core residue before attacking a second chain, alpha RNase H is a random exoribonuclease that releases the polynucleotide after each scission. Highly purified Moloney-MSV(MLV) DNA polymerase has both RNase H activity and the ability to read viral 60-70S RNA. These activities comigrate through five different steps of purification and are present at levels comparable to those found in purified AMV DNA polymerase. The MSV(MLV) 60-70S RNA genome and 35S RNA subunits were shown by periodate oxidationtritiated borohydride reduction to contain adenosine as the major 3'-terminal nucleoside. Poly (A) segments were isolated from viral 60-70S and 35S RNA by treatment with RNase A or RNase T1 and purified by afinity chromatography and gel electrophoresis. Viral poly(A) was shown to be present at the 3' terminus as -G(C,U)A190AOH. The similar sequence reported for poly(A) present in mammalian mRNA suggests that similar mechanisma are involved in the transcription and processing of both cellular and viral DNA sequences. Within transformed cells replicating MSV(MLV), viral 35S and 20S RNA were found in membrane-bound polyribosomes, whereas only 35S RNA was detected in free polyribosomes. The origin and function of 20S RNA is unknown. The early events during rapid infection and cell transformation of mouse 3T6 cells by the Harvey strain of MSV(MLV) were studied. By both autoradiographic analysis and molecular hybridization, viral DNA synthesis was detected in the cytoplasm by 1 hour after infection, reached a maximum at 2 hours, and subsequently decreased. Cytological chase experiments produced evidence that cytoplasmic viral DNA was transported to the nucleus. In situ hybridization experiments using radioactive viral DNA product as a probe demonstrated the rapid association of viral DNA sequences with the chromocenters of interphase nuclei and with the centromeric heterochromatin regions of some chromosomes.
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PMID:Properties of oncornavirus RNA-directed DNA polymerase, the RNA template, and the intracellular products formed early during infection and cell transformation. 5 Sep 2

Earlier we reported that herpes simplex virus 1 DNA contains a sequence which binds a host protein in a sequence-specific manner as either a single-stranded or a double-stranded DNA or RNA and that this sequence is located in a transcriptional unit whose RNA traverses the origin of viral DNA replication (OriSRNA) (R.J. Roller, L. McCormick, and B. Roizman, Proc. Natl. Acad. Sci. USA 86:6518-6522, 1989). The protein reacts with both DNA and RNA in band-shift assays and protects the single-stranded RNA sequence from digestion by RNase. We report that the minimal cognate sequence required for these interactions consisted of [N(GTGGGTGGG)2(N less than or equal to 10)]. The ninemer repeat sequence was located at nucleotides -1 to -18 relative to the transcription initiation of the major species of OriSRNA. The activity of the cognate sequence required at least three guanines between thymines and tolerates the insertion of additional thymines, but it was inactivated by the insertion of adenines or by the substitution of some of the guanines with cytosines in one repeat. Replacement of the 10 3' nucleotides has no effect on binding activity, whereas deletion of these sequences abolished it. Among the related sequences with no demonstrable binding activity were some telomeric sequences which interact with known cognate proteins. The electrophoretic mobility of the herpes simplex virus cognate sequences in nondenaturing gels suggests that they may be able to form higher-order structures, but the conditions under which they were formed were different from the optimal conditions for binding the protein. UV light cross-linking studies of labeled RNA-protein complexes following digestion with RNases indicated that the electrophoretic mobility of the protective activity corresponded to that of a protein with an apparent molecular weight of 100,000.
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PMID:Characterization of a herpes simplex virus sequence which binds a cellular protein as either a single-stranded or double-stranded DNA or RNA. 131 59

An antinuclear antibody specific for nuclear membrane (ANMA) was observed by the immunofluorescence method in sera from patients with primary biliary cirrhosis (PBC). ANMA was present in 18 of 63 PBC sera (28.5) and in 1 of 431 control sera (0.2%). Its reaction appeared as a thin fluorescent ring confined to the nuclear envelope and was more evident when the sera were highly diluted and the fluorescence, due to frequently associated antimitochondrial antibody, faded. The ANMA fluorescent pattern was confirmed by indirect immunoperoxidase staining. ANMA was seen on both tissue cryostat sections and HEp-2 cells. It was a poorly or non-complement-fixing IgG, specific for an antigen resistant to DNase I, RNase, and trypsin. The significance of its presence in PBC in unknown at present. Identification of its antigen with one of the centromeric antigens is suggested.
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PMID:Nuclear membrane-staining antinuclear antibody in patients with primary biliary cirrhosis. 241 13

A telomere terminal transferase activity was identified in developing macronuclear extracts from Euplotes crassus. The activity was essentially unregulated in vitro: up to 50 tandem repeats of the Euplotes telomeric repeat sequence TTTTGGGG were added onto synthetic telomeric oligonucleotide primers. Both the structure of the telomere substrate and its 3'-terminal sequence were recognized. The activity was destroyed by low concentrations of RNase A.
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PMID:Telomere terminal transferase activity from Euplotes crassus adds large numbers of TTTTGGGG repeats onto telomeric primers. 247 61

Antibodies to DNA in the left-handed (Z) conformation bind to acid-fixed polytene chromosomes of both Chironomus thummi and Drosophila melanogaster, as shown by direct and indirect immunofluorescence. Comparison of the phase-contrast, immunofluorescence, and DNA staining patterns shows a predominant localization of the antibody to the regions of high contrast and DNA density, the bands. The immunofluorescence is completely abolished by competition with polynucleotides in the Z conformation but not by those in the B form. DNase but not RNase treatment eliminates the antibody staining. Actinomycin D inhibits binding, whereas mithramycin has no effect. The highly reproducible immunofluorescence patterns obtained with the anti-Z-DNA antibodies demonstrate variations in fluorescence intensity between particular bands, which can be quantitated by laser scanning and photon counting techniques. The telomeric regions and DNA strands associated with end-to-end chromosome linkage and ectopic pairing are exceptionally bright. At saturation, average values of 1 IgG molecule per 3,000 base pairs and 1 per 15,000 base pairs are found in the intensely and weakly staining regions, respectively. An alternative statement is that the left-handed Z-DNA conformation is present at a frequency of 0.02-0.1%. The measured differences reflect variations in the local density of Z-DNA sites and not in the affinity for the specific antibody, which appears to be relatively constant throughout the chromosomes (Kd approximately equal to 10 nM). These observations taken together with results of biophysical studies on the properties of Z-DNA in solution suggest that regions of DNA in the left-handed conformation could be involved in higher-order structural organization of chromosomes and possibly in modulation of their functional state.
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PMID:Left-handed Z-DNA in bands of acid-fixed polytene chromosomes. 641 Mar 90

DNA strandness changes occurring during in situ hybridization were monitored using monoclonal antibodies. Our results show that: 1) RNase induces formation of single stranded DNA, 2) after denaturation-renaturation, single stranded DNA is found principally in centromeric areas, and 3) double stranded DNA is still observed after each step.
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PMID:DNA strandness changes during in situ hybridization conditions. 751 May 36

Telomerase activity was demonstrated in cell-free extracts from S. cerevisiae through the use of a PCR-based assay. As expected, this activity was eliminated by RNase or phenol treatment of the extract and was dependent on dGTP and dTTP. Telomerase was not detected in extracts prepared from cells grown for approximately 30 or more cell divisions in the absence of the EST1 product, Est1p. TLC1 RNA, which determines the sequence of telomeric DNA in vivo, was present in normal amounts in est1 delta cells. Moreover, TLC1 RNA specifically precipitated with epitope-tagged Est1p. These data indicate that Est1p is either a subunit of yeast telomerase or an accessory protein associated with telomerase that is essential in vitro for its activity.
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PMID:An in vitro assay for Saccharomyces telomerase requires EST1. 760 May 80

The arrangement of loops and chromomeres at the ends of lampbrush chromosomes in four species of bird is described with reference to chromomeres, loops and transcription units. Unlike the situation described in lampbrush chromosomes of amphibians, the lampbrush chromosomes of birds end in a terminal chromosome with conspicuous loops emerging from it. The fine-scale morphology of the ribonuclear protein matrix of these terminal loops is different from that of the majority of loops elsewhere on the chromosomes. In many cases the loops associated with the terminal chromomere are open ended, emerging from the chromomere but not returning to it at the other end. The distal ends of terminal open-ended loops therefore represent the true ends of the chromatids that make up a lampbrush half-bivalent. The pattern of binding of three telomeric DNA sequence probes to the terminal regions of bird lampbrush chromosomes, under conditions of DNA/DNA and DNA/RNA transcript in situ hybridization has been investigated by fluorescence in situ hybridization. All three probes gave the same results. With DNA/DNA and DNA/RNA transcript hybridization, three classes of structure were labelled: the terminal chromomere, a small number of interstitial chromomeres and the terminal transcription unit on telomere loops. Labelling of telomere loops, but not of terminal or interstitial chromomeres, was eliminated by ribonuclease treatment before in situ hybridization. The labelled regions of telomere loops were spaced away from the labelled terminal chromomere by an unlabelled sub telomeric transcription unit. After DNA/DNA in situ hybridization, no labelled loops were seen. DNA/RNA transcript in situ hybridization with single-stranded hexamers of each strand of telomeric DNA showed that the terminal transcription unit on telomere loops represents transcription exclusively from the C-rich strand of the repeat outwards towards the end of the chromosome. It is concluded that transcription specifically of the C-rich strand of strictly terminal clusters of telomere repeats is an obligatory event on the lampbrush chromosomes of birds and is unlikely to represent indiscriminate readthrough from proximally located gene elements.
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PMID:The arrangement and transcription of telomere DNA sequences at the ends of lampbrush chromosomes of birds. 783 23

Telomerase activity was identified in extracts from several different mouse cell lines. Addition of telomeric TTAGGG repeats was specific to telomeric oligonucleotide primers and sensitive to pretreatment with RNase A. In contrast to the hundreds of repeats synthesized by the human and Tetrahymena telomerase enzymes in vitro, mouse telomerase synthesized only one or two TTAGGG repeats onto telomeric primers. The products observed after elongation of primers with circularly permuted (TTAGGG)3 sequences and after chain termination with ddATP or ddTTP indicated that mouse telomerase pauses after the addition of the first dG residue in the sequence TTAGGG. The short length of the products synthesized by mouse telomerase was not due to a diffusible inhibitor in the mouse extract, because the human telomerase continued to synthesize long products when mixed with mouse fractions. Primer challenge experiments showed that the human enzyme synthesized long TTAGGG repeats processively in vitro, whereas the mouse telomerase appeared to be much less processive. The identification of short telomerase reaction products in mouse extracts suggests that extracts from other organisms may also generate only short products. This knowledge may aid in the identification of telomerase activity in organisms where activity has not yet been detected.
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PMID:Identification of a nonprocessive telomerase activity from mouse cells. 843 10

We describe a method of selectively enriching for murine telomere-proximal sequences using affinity capture followed by PCR amplification. The telomeric fragments were selected from NotI-digested and lambda exonuclease-resected mouse genomic DNA by annealing to a biotinylated riboprobe containing multiple copies of the telomere repeat (TTAGGG)n. The resultant DNA-RNA hybrids were selectively retained on a matrix with covalently bound avidin. The captured DNA was then specifically released by ribonuclease action, and PCR amplification was performed using mouse repeat primers. The PCR products were cloned and used to screen a mouse genomic cosmid library, and the resultant cosmid clones were analyzed by fluorescence in situ hybridization. Ten of 70 clones analyzed gave telomere-proximal hybridization signals, indicating an at least 500-fold enrichment for telomere-proximal sequences.
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PMID:Isolation of murine telomere-proximal sequences by affinity capture and PCR. 857 53


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