Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Following EMS mutagenesis we recovered a mutant of D. melanogaster that grows at concentrations of alpha-amanitin lethal to wild-type. To our knowledge this mutant represents the first example of an amanitin-resistant eucaryotic organism. The amanitin resistance of the mutant (AmaC4) is due to an alteration in its DNA-dependent RNA polymerase II, which is approximately 250 times less sensitive to inhibition by amanitin than the wild-type polymerase II whether tested in nuclei, in partially-fractionated extracts or as a highly purified enzyme. While the wild-type enzyme activity is inhibited 50% by 2.1 x 10(-8) M alpha-amanitin, inhibition of 50% of the AmaC4 RNA polymerase II activity requires a toxin concentration of 5.6 x 10(-6) M. The mutation responsible for the amanitin resistance of AmaC4 is on the X chromosome near the vermillion locus.
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PMID:Alpha-amanitin-resistant D. melanogaster with an altered RNA polymerase II. 11

Spontaneous and EMS-induced alpha-amanitin-resistant Aedes albopictus cells have been isolated and characterized. Two mutant sublines, one of intermediate resistance (alpha A2) and the other highly resistant (Ama18) contained RNA polymerase II activity, the resistance of which in vitro to alpha-amanitin correlated well with the resistance of these cells in vivo. The resistance of these cells to alpha-amanitin can likely be attributed to the presence of an altered RNA polymerase II.
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PMID:alpha-Amanitin resistant RNA polymerase II from Aedes albopictus cell mutants resistant to alpha-amanitin. 50 43

Spontaneous and EMS-induced alpha-amanitin-resistant CHO cells have been isolated and characterized. DNA-dependent RNA polymerase II in cell-free extracts from a mutant (ARM-1) was partially resistant to alpha-amanitin. Growing mutants for several generations in the presence or absence of alpha-amanitin did not change the pattern of inhibition. The mutants grew with a lag following transfer to medium with or without alpha-amanitin. The mutants have an altered RNA polymerase II, and possibly an altered cell membrane.
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PMID:alpha-Amanithin-resistant mutants of Chinese hamster ovary (CHO) cells. 62 84

Mutations in the Caenorhabditis elegans dpy-13 (dumpy) gene result in a short, chunky body shape. This gene was tagged by insertion of the Tc1 transposon, and the wild-type gene was cloned by chromosomal walking 11 kb from ama-1, a cloned gene encoding the large subunit of RNA polymerase II. Three transposon insertion sites in dpy-13 are located near the 5' end of a 1.2 kb transcribed region. The EMS-induced reference allele, dpy-13(e184), carries a small deletion near the middle of this gene. The DNA sequence reveals that dpy-13 is a member of the collagen multi-gene family, and it could encode a polypeptide of 302 amino acids. A 146 base pair sequence, encoding amino acids 56-103, is unique in the C. elegans genome, and it hybridizes to a 1 kb mRNA of moderate abundance.
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PMID:dpy-13: a nematode collagen gene that affects body shape. 284 84

Mutants of Caenorhabditis elegans resistant to alpha-amanitin have been isolated at a frequency of about 1.6 x 10(-6) after EMS mutagenesis of the wild-type strain, N2. Four new dominant resistance mutations have been studied genetically. Three are alleles of a previously identified gene, ama-1 IV, encoding the largest subunit of RNA polymerase II. The fourth mutation defines a new gene, ama-2 V. Unlike the ama-1 alleles, the ama-2 mutation exhibits a recessive-lethal phenotype. Growth and reproduction of N2 was inhibited at a concentration of 10 micrograms/ml amanitin, whereas ama-2/+ animals were inhibited at 100 micrograms/ml, and 800 micrograms/ml was required to inhibit growth of ama-1/+ larvae. We have also determined that two reference strains used for genetic mapping, dpy-11(e224)V and sma-1(e30)V, are at least four-fold more sensitive to amanitin that the wild-type strain. Using an amanitin-resistant ama-1(m118) or ama-1(m322) strain as a parent, we have isolated amanitin-sensitive mutants that carry recessive-lethal ama-1 alleles. The frequency of EMS-induced lethal ama-1 mutations is approximately 1.7 x 10(-3), 1000-fold higher than the frequency of amanitin-resistance alleles. Nine of the lethal alleles are apparent null mutations, and they exhibit L1-lethal phenotypes at both 20 degrees and 25 degrees. Six alleles result in partial loss of RNA polymerase II function as determined by their sterile phenotypes at 20 degrees. All but one of these latter mutations exhibit a more severe phenotype at 25 degrees C. We have also selected seven EMS-induced revertants of three different ama-1 lethals. These revertants restore dominant resistance to amanitin. The selection for revertants also produced eight new dominant amanitin resistance alleles on the balancer chromosome, nT1.
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PMID:Lethal and amanitin-resistance mutations in the Caenorhabditis elegans ama-1 and ama-2 genes. 319 54

A fine-structure genetic map has been constructed for ama-1 IV, an essential gene in Caenorhabditis elegans encoding the amanitin-binding subunit of RNA polymerase II. Sixteen EMS-induced recessive-lethal mutations have been positioned in the gene by determining their intragenic recombination frequencies with m118, a mutation that confers dominant resistance to alpha-amanitin. The 16 mutants, all isolated in the ama-1(m118) background, include 13 that are early larval lethals, and three that are mid-larval lethals, at 25 degrees. Six of the mutants exhibit temperature-dependence in the severity of their phenotype. Intragenic recombination between the lethal site and the parental resistance mutation was detected by means of resistance to amanitin. Recombinants were detected at frequencies as low as 2 X 10(-6). The segregation of the closely linked flanking markers, unc-17 and unc-5, revealed whether the lethal mutation was to the left or the right of m118. By adding the distances between the extreme left and right mutations, the ama-1 gene is estimated to be 0.011 map unit long, with m118 positioned 0.004 map unit from the left-most lethal mutation. To order the lethal mutations with respect to each other, viable heteroallelic strains were constructed using the free duplication, mDp1[unc-17(e113) dpy-13(+) ama-1(+)]. The heteroallelic strains were sensitive to amanitin, and recombination events between the lethal mutations were specifically selected by means of the dominant amanitin resistance encoded on the recombinant chromosome. The segregation of outside markers revealed the left-right order of the lethal mutations. The position of mutations within the gene is nonrandom. Functional domains of the ama-1 gene indicated by the various lethal phenotypes are discussed.
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PMID:Fine-structure genetics of ama-1, an essential gene encoding the amanitin-binding subunit of RNA polymerase II in Caenorhabditis elegans. 319 55

We previously described an alpha-amanitin-resistant mutant of D. melanogaster (AmaC4 or simply C4) with an altered, amanitin-resistant RNA polymerase II. We have now more fully characterized this mutant genetically and biochemically. We genetically mapped C4 to position 35.66 on the X chromosome and cytogenetically localized it to the polytene chromosome band interval 10C2-10D4. We then demonstrated that C4 is allelic to a previously known lethal-mutable locus I(1)L5 in this chromosomal region. Several known lethal alleles of L5 in fact affected the properties of RNA polymerase II in vitro. Following EMS mutagenesis of the C4-bearing chromosome we recovered new lethal L5 alleles, some of which were shown biochemically to have an altered amanitin-resistance polymerase II component. Furthermore, we induced mutants of C4 that had lost amanitin-resistance and showed that these mutants were also lethal alleles of L5. All the lethal alleles of L5 failed to completely complement each other genetically, and when analyzed biochemically their polymerase II displayed altered enzymatic properties. We conclude that C4 is an allele of the L5 locus and that this locus is most probably a structural gene for a subunit of RNA polymerase II. Some of the mutants at this locus display developmental abnormalities.
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PMID:Genetic and biochemical characterization of mutants at an RNA polymerase II locus in D. melanogaster. 677 48

An EMS-induced, sex-linked recessive lethal mutation that in heterozygous condition mimics the third-chromosome dominant mutant Ultrabithorax-130 (Ubx130) has been discovered in Drosophila melanogaster. This Ultrabithorax-like (Ubl) mutant, when heterozygous, adds several hairs to and enlarges the apical segment (capitellum) of the haltere. Ubl fails to complement Ubln [previously called l (1) L5], a recessive lethal null allele located in section 10C of Bridges' (1938) map of the polytene X chromosome at map position 35.7 Ubl behaves as an antimorph: heterozygous deficiencies for section 10C do not display the Ubl dominant phenotype. Ubl shows a dosage effect: the maximum expression occurs in females with the genotype Ubl/Ubl; Dp Ubl+, in which the capitellum is about three times as large as that of Ubl/+, with two or more rows of bristles. These flies are poorly viable and sterile when mated to Ubl; Dp Ubl+ males, but produce a few offspring when mated to Ubl+ males. Ubl displays a complex series of interactions with loci other than Ubx and elicits expression of specific mutant phenotypes when it is heterozygous in trans with certain nonallelic deficiencies and recessive mutations. Greenleaf et al. (1980) have demonstrated thatUbl is allelic with an alpha-amanitin-resistant mutation that effects RNA polymerase II; therefore, the interactions observed between Ubl and other loci may result from an inability of heterozygous Ubl flies to undergo normal transcription.
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PMID:An RNA polymerase II mutation in Drosophila melanogaster that mimics ultrabithorax. 678 43

Purified RNA polymerase II (RNA nucleotidyl-transferase; EC 2.7.7.6) extracted from flies possessing lesions in the Ultrabithorax-like (Ubl) locus of Drosophila melanogaster has altered activity in vitro (Greenleaf et al. 1979, 1980; Coulter and Greenleaf 1982). This strongly suggests that the Ubl locus encodes a subunit of RNA polymerase II. Ethyl methanesulfonate was used to induce a temperature-sensitive mutation in this locus. Flies either homozygous or hemizygous for this new X-linked mutation (Ublts) display viability comparable to that of wild-type flies at 22 degrees C but are lethal at 29 degrees C. The temperature-sensitive period for Ublts flies is between gastrulation (6 h, 29 degrees C) and pupation (9-10 days, 22 degrees C). Zygotes shifted from 22 degrees C to 29 degrees C die at either the late embryonic or first larval instar stage while temperature shifts of second and third instar larvae result in the lethal phase occurring at the pupal stage. Most pupae shifted from 22 degrees C to 29 degrees C undergo metamorphosis and eclose as adults. Adults are viable if placed at 29 degrees C; however, all females and some males become sterile if maintained at this temperature. Somatic recombination was used to induce clones homozygous for a null allele of Ubl at different stages of development. Clones of this null allele appear to be cell lethal indicating that the Ubl+ gene product is required at all stages of development. The viability of Ublts pupae and adults at 29 degrees C may result from only a partial reduction in activity caused by the mutation at this nonpermissive temperature.
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PMID:Developmental genetics of a temperature-sensitive RNA polymerase II mutation in Drosophila melanogaster. 681 24

The amanitin-binding subunit of RNA polymerase II in Caenorhabditis elegans is encoded by the ama-1 gene, located approximately 0.05 map unit to the right of dpy-13 IV. Using the amanitin-resistant ama-1(m118) strain as a parent, we have isolated amanitin-sensitive mutants that carry recessive-lethal ama-1 alleles. Of the six ethyl methanesulfonate-induced mutants examined, two are arrested late in embryogenesis. One of these is a large deficiency, mDf9, but the second may be a novel point mutation. The four other mutants are hypomorphs, and presumably produce altered RNA polymerase II enzymes with some residual function. Two of these mutants develop into sterile adults at 20 degrees but are arrested as larvae at 25 degrees, and two others are fertile at 20 degrees and sterile at 25 degrees. Temperature-shift experiments performed with the adult sterile mutant, ama-1(m118m238ts), have revealed a temperature-sensitive period that begins late in gonadogenesis and is centered around the initiation of egg-laying. Postembryonic development at 25 degrees is slowed by 30%. By contrast, the amanitin-resistant allele of ama-1 has very little effect on developmental rate or fertility. We have identified 15 essential genes in an interval of 4.5 map units surrounding ama-1, as well as four gamma-ray-induced deficiencies and two duplications that include the ama-1 gene. The larger duplication, mDp1, may include the entire left arm of chromosome IV, and it recombines with the normal homologue at a low frequency. The smallest deficiency, mDf10, complements all but three identified genes: let-278, dpy-13 and ama-1, which define an interval of only 0.1 map unit. The terminal phenotype of mDf10 homozygotes is developmental arrest during the first larval stage, suggesting that there is sufficient maternal RNA polymerase II to complete embryonic development.
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PMID:A Caenorhabditis elegans RNA polymerase II gene, ama-1 IV, and nearby essential genes. 860 33


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