Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Neurospora”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1998

Structure of the chromosome VII centromere region in Neurospora crassa: degenerate transposons and simple repeats.

DNA from the centromere region of linkage group (LG) VII of Neurospora crassa was cloned previously from a yeast artificial chromosome library and was found to be atypical of Neurospora DNA in both composition (AT rich) and complexity (repetitive). We have determined the DNA sequence of a small portion (approximately 16.1 kb) of this region and have identified a cluster of three new retrotransposon-like elements as well as degenerate fragments from the 3' end of Tad, a previously identified LINE-like retrotransposon. This region contains a novel full-length but nonmobile copia-like element, designated Tcen, that is only associated with centromere regions. Adjacent DNA contains portions of a gypsy-like element designated Tgl1. A third new element, Tgl2, shows similarity to the Ty3 transposon of Saccharomyces cerevisiae. All three of these elements appear to be degenerate, containing predominantly transition mutations suggestive of the repeat-induced point mutation (RIP) process. Three new simple DNA repeats have also been identified in the LG VII centromere region. While Tcen elements map exclusively to centromere regions by restriction fragment length polymorphism analysis, the defective Tad elements appear to occur most frequently within centromeres but are also found at other loci including telomeres. The characteristics and arrangement of these elements are similar to those seen in the Drosophila centromere, but the relative abundance of each class of repeats, as well as the sequence degeneracy of the transposon-like elements, is unique to Neurospora. These results suggest that the Neurospora centromere is heterochromatic and regional in character, more similar to centromeres of Drosophila than to those of most single-cell yeasts.

Algorithms↗
PubMed2003

Phosphorylation of FREQUENCY protein by casein kinase II is necessary for the function of the Neurospora circadian clock.

FREQUENCY (FRQ), a key component of the Neurospora circadian clock, is progressively phosphorylated after its synthesis. Previously, we identified casein kinase II (CKII) as a kinase that phosphorylates FRQ. Disruption of the catalytic subunit of CKII abolishes the clock function; it also causes severe defects in growth and development. To further establish the role of CKII in clock function, one of the CKII regulatory subunit genes, ckb1, was disrupted in Neurospora. In the ckb1 mutant strain, FRQ proteins are hypophosphorylated and more stable than in the wild-type strain, and circadian rhythms of conidiation and FRQ protein oscillation were observed to have long periods but low amplitudes. These data suggest that phosphorylation of FRQ by CKII regulates FRQ stability and the function of the circadian feedback loop. In addition, mutations of several putative CKII phosphorylation sites of FRQ led to hypophosphorylation of FRQ and long-period rhythms. Both CKA and CKB1 proteins are found in the cytoplasm and in the nucleus, but their expressions and localization are not controlled by the clock. Finally, disruption of a Neurospora casein kinase I (CKI) gene, ck-1b, showed that it is not required for clock function despite its important role in growth and developmental processes. Together, these data indicate that CKII is an important component of the Neurospora circadian clock.

Biological Clocks↗
PubMed2003

Synthesis of signals for de novo DNA methylation in Neurospora crassa.

Most 5-methylcytosine in Neurospora crassa occurs in A:T-rich sequences high in TpA dinucleotides, hallmarks of repeat-induced point mutation. To investigate how such sequences induce methylation, we developed a sensitive in vivo system. Tests of various 25- to 100-bp synthetic DNA sequences revealed that both T and A residues were required on a given strand to induce appreciable methylation. Segments composed of (TAAA)(n) or (TTAA)(n) were the most potent signals; 25-mers induced robust methylation at the special test site, and a 75-mer induced methylation elsewhere. G:C base pairs inhibited methylation, and cytosines 5' of ApT dinucleotides were particularly inhibitory. Weak signals could be strengthened by extending their lengths. A:T tracts as short as two were found to cooperate to induce methylation. Distamycin, which, like the AT-hook DNA binding motif found in proteins such as mammalian HMG-I, binds to the minor groove of A:T-rich sequences, suppressed DNA methylation and gene silencing. We also found a correlation between the strength of methylation signals and their binding to an AT-hook protein (HMG-I) and to activities in a Neurospora extract. We propose that de novo DNA methylation in Neurospora cells is triggered by cooperative recognition of the minor groove of multiple short A:T tracts. Similarities between sequences subjected to repeat-induced point mutation in Neurospora crassa and A:T-rich repeated sequences in heterochromatin in other organisms suggest that related mechanisms control silent chromatin in fungi, plants, and animals.

AT Rich Sequence↗
PubMed1986

Primary structure and spectroscopic studies of Neurospora copper metallothionein.

When Neurospora crassa is grown in the presence of Cu(II) ions, it accumulates the metal with the concomitant synthesis of a low molecular weight copper-binding protein. The molecule binds 6 g-atom of copper per mole protein (Mr = 2200) and shows a striking sequence homology to the zinc- and cadmium-binding vertebrate metallothioneins. Absorption, circular dichroism, and electron paramagnetic resonance spectroscopy of Neurospora metallothionein indicate the copper to be bound to cysteinyl residues as a Cu(I)-thiolate complex of the polymeric mu-thiolate structure [Cu(I)6RS7]-. This metal-binding mode is also in agreement with the unusual luminescence of the protein. Spectral perturbation studies with HgCl2 and p-(chloromercuri)benzoate suggest that the 6 Cu(I)ions are coordinated to the seven cysteinyl residues in the form of a single metal cluster. Neurospora apometallothionein is also capable of binding in vivo group IIB metal ions [Zn(II), Cd(II), and Hg(II)] as well as paramagnetic Co(II) ions with an overall metal-to-protein stoichiometry of 3. The spectroscopic properties of the fully substituted forms are indicative of a distorted tetrahedral coordination. However, metal titration of the apoprotein shows the third metal ion to be differently coordinated than the other two metal ions. This difference can be explained by the presence of only seven cysteine residues in Neurospora metallothionein as opposed to nine cysteine residues in the three-metal cluster of the mammalian metallothioneins.

Amino Acid Sequence↗
PubMed1997

A kinesin-like mechanoenzyme from the zygomycete Syncephalastrum racemosum shares biochemical similarities with conventional kinesin from Neurospora crassa.

The kinesin superfamily consists of mechanoenzymes that convert chemical energy, stored in nucleoside triphosphates, into movement along microtubules. The founding member of this protein superfamily, the so-called conventional kinesin, was only known from animal sources until the recent description of kinesin from the filamentous fungus Neurospora crassa (G. Steinberg, M. Schliwa, Mol. Biol. Cell 6, 1605-1618 (1995)). To determine whether similar motors with comparable features are common in other filamentous fungi, a kinesin from a zygomycete, Syncephalastrum racemosum, was purified. Here, the isolation and characterization of this motorenzyme is described. The purified protein consisted of a doublet at 112 kDa and 115 kDa with no additional polypeptides. This was consistent with a calculated molecular mass of approximately 240 kDa and suggests that the motor is a dimer with a more globular shape than conventional kinesin from animal sources. In gliding assays the enzyme moved microtubules at 2.5 to 3.4 microns/s and had a nucleotide specificity similar to the Neurospora kinesin motor. Peptide antibodies against conserved regions in the head and the tall domain of conventional kinesins cross-reacted with the Syncephalastrum motor. In vitro, the enzyme was able to drive the microtubule-dependent movement of vesicles isolated from Syncephalastrum racemosum, as well as Neurospora crassa, and Aspergillus nidulans. In summary, the Syncephalastrum motor has many of the unique features in common with the conventional kinesin from the ascomycete Neurospora crassa and probably shares a similar function in living hyphae.

Animals↗
PubMed1984

Nucleotide sequence of the cloned mRNA and gene of the ADP/ATP carrier from Neurospora crassa.

A cDNA complementary to the mRNA of the ADP/ATP carrier from Neurospora crassa was identified among ordered cDNA clones by hybridizing total polyadenylated RNA to pools of 96 cDNA recombinant plasmids and subsequent cell-free translation of hybridization-selected mRNA. Further carrier cDNAs were found by colony filter hybridization at a frequency of 0.2-0.3%. The gene of the carrier was cloned and isolated on a 4.6-kbp EcoRI fragment of total Neurospora DNA, and the start of the mRNA was determined by S1 nuclease mapping. From the nucleotide sequence of the cDNA and the genomic DNA, the primary structure of the gene, of the mRNA and of the ADP/ATP carrier protein could be deduced. The gene occurs in a single copy in the genome and related genes are absent. It contains two short introns, and a pyrimidine-rich promoter region. The mRNA has a 46-bp 5' end and a 219-bp 3' end. There is an open reading frame coding for the 313 amino acid residues of the Neurospora carrier protein. The amino acid sequence is homologous in 148 positions with the established primary structure of the beef heart carrier.

Base Sequence↗
PubMed1976

Genetic and metabolic regulation of purine base transport in Neurospora crassa.

Neurospora crassa can utilize various purine bases such as xanthine or uric acid and their catabolic products as a nitrogen source. The early purine catabolic enzymes in this organism are regulated by induction and by ammonium repression. Studies were undertaken to investigate purine base transport and its regulation in Neurospora. The results of competition experiments with uric acid and xanthine transport strongly suggest that uric acid and xanthine share a common transport system. It was also shown that the common transport system for uric acid and xanthine is distinct from a second transport system shared by hypoxanthine, adenine and guanine, and apparently also distinct from the transport system(s) for adenosine, cytosine and uracil. Regulation of the uric acid-xanthine transport system and the hypoxanthine-adenine-guanine transport system was studied. The results reveal that the uric acid-xanthine transport system is regulated by ammonium repression, but does not require uric acid induction. Neither ammonium repression nor uric acid induction controls the hypoxanthine-adenine-guanine transport system. A gene, designated amr, which is believed to be a positive regulatory gene for nitrogen metabolism of Neurospora crassa, was found to dramatically affect both the uric acid-xanthine transport system and the hypoxanthine-adenine-guanine transport system. A model for the action of the amr locus as a positive regulatory gene and for the interaction between the amr gene product and its recognition sites will be discussed.

Binding, Competitive↗
PubMed1987

Orientation of enzymic domains in tryptophan synthase of Neurospora crassa: an immunoblot analysis of TRP3 mutant products.

Extracts of 52 TRP3 mutants of Neurospora crassa were tested for the presence of serologically cross-reacting material by the method of electrophoretic blot analysis. The test antigen was obtained by excision of lightly stained bands of denatured pure tryptophan synthase after SDS-polyacrylamide gel electrophoresis. Rabbit antisera raised against this antigen neutralized and precipitated native tryptophan synthase. Of the 52 strains, 19 exhibited banding patterns similar to wild type on electrophoretic blots, 25 strains gave no apparent bands, and 8 strains showed unique banding patterns. This evidence and related genetic fine structure mapping data indicate that strains exhibiting banding patterns similar to wild type carry missense mutations. Strains which did not exhibit any obvious bands may have resulted from certain kinds of missense or nonsense mutations or from frameshift mutations or extended deletions. Strains exhibiting unique banding patterns on electrophoretic blots were interpreted as carrying chain-terminating mutations or deletions. Genetic fine structure mapping data place the mutant lesions of these strains in a linear order corresponding to the apparent molecular weights of the crossreacting protein fragments which they exhibit. The direction of transcription and translation of the TRP3 locus in Neurospora was inferred from these relationships. The apparent organization of the Neurospora TRP3 gene is consistent with that ascribed to the Saccharomyces TRP5 system and suggests that the N-terminal portion of the protein corresponds to the "A" protein of the Escherichia coli system and that the C-terminal portion of the protein corresponds to the "B" protein of the bacterial system.

Crosses, Genetic↗
PubMed1987

Phylogenetic implication of heterogeneity of the nontranscribed spacer of rDNA repeating unit in various Neurospora and related fungal species.

Nontranscribed spacer (NTS) regions of ribosomal (r)RNA genes are non-conserved and are shown to be useful for phylogenetic studies. 32P-labelled N. crassa NTS pCC3400 DNA, was used as a molecular probe to hybridize Southern blots of genomic DNAs obtained from Neurospora, Gelacinospora, Sordaria, bacteria, plants, and animals. Our studies conclude that: (a) the homotahllic species of Neurospora should not belong to genus Gelacinospora (a historical question) and that Neurospora homothallic species are closer to Gelacinospora than to Sordaria; and that (b) all of the filamentous fungal species tested are indeed closer to the higher plant genome than to higher primate animal genome based on shared restriction sites of 12 enzymes. Our studies also demonstrate the usefulness of nontranscribed rRNA gene probes in resolving questions regarding phylogenetic relatedness between widely separated organisms using the parsimony principle based on mutation sites from DNA restriction maps; it has not been possible to do this using DNA: DNA hybridization procedures that involved the total genome.

DNA Restriction Enzymes↗
PubMed1988

Cyclic AMP-dependent, constitutive thermotolerance in the adenylate cyclase-deficient cr-1 (crisp) mutant of Neurospora crassa.

We investigated the heat shock response of the adenylate cyclase deficient mutant cr-1 (crisp) of Neurospora crassa. This strain was observed to be much more resistant to a lethal temperature of 50 degrees C than the wild type. This constitutive thermotolerance was absent in cr-1 conidiospores raised on cyclic AMP (cAMP, 2.5 mM) supplemented solid medium, but was partially restored when the conidiospores were germinated at 30 degrees C, a temperature which fails to induce thermotolerance in the wild-type strain. Two other crisp-like Neurospora mutants, cr-2 and cr-3 which, in contrast to cr-1, contain normal levels of cAMP, did not exhibit the thermotolerance phenomenon observed for cr-1. A cr-1, pe, fl (crisp-microconidial) strain also lacked the ability to tolerate a lethal heat treatment. Our results demonstrate that the adenylate cyclase deficient cr-1 mutant of Neurospora crassa expresses a constitutive thermotolerant phenotype as a consequence of its primary genetic defect: low levels of cAMP.

Adenylyl Cyclases↗
PubMed1982

Regulation of L-amino acid oxidase and of D-amino acid oxidase in Neurospora crassa.

Neurospora crassa possesses an inducible L-amino acid oxidase that is expressed only when cells are derepressed for nitrogen in the presence of an amino acid. Enzyme synthesis requires both induction by an amino acid and simultaneous nitrogen catabolite derepression. Carbon limition in the presence of an amino acid does not permit induction of L-amino acid oxidase. The nit-2 gene is a major regulatory locus which is believed to mediate nitrogen catabolite repression in Neurospora. Mutants of nit-2 are repressed for L-amino acid oxidase activity under conditions which lead to good enzyme induction in wild type and nit-2 revertants. The loss of the enzyme in nit-2 mutants does not result from inducer exclusion, which suggests that the nit-2 gene product has a direct role in controlling the expression of this enzyme. Substantial amounts of L-amino acid oxidase were detected in the growth medium as well as in cell extracts of the wild type strain. Biochemical data indicates that the intracellular and the extracellular L-amino acid oxidases are identical. Inhibitors of protein and of RNA synthesis block accumulation of L-amino acid oxidase, suggesting that enzyme expression is controlled at the level of transcription. D-amino acid oxidase can be detected in cell extracts of Neurospora grown in the presence of a D-amino acid. The enzyme is present in cys-3 mutants and is not repressed by high concentrations of sulfate or nitrogen indicating that D-amino acid oxidase is not a member of the sulfur or nitrogen regulatory circuits of this organism.

Amino Acid Oxidoreductases↗
PubMed1984

Preparation of a cell-free translation system from a wild-type strain of Neurospora crassa and translation of pyruvate kinase messenger RNA.

A cell-free in vitro translation system exhibiting high activity has been developed from wild-type Neurospora crassa mycelium. The isolation is simple and fast, and the homogenization does not appear to affect the activity of mycelial proteases and nucleases. This system is capable of supporting efficient translation of exogenously added homologous RNA as demonstrated by the experiments with PK-specific mRNA. In addition, it translates heterologous RNA efficiently, shown by the translation of globin mRNA. We did not examine the Neurospora lysate for post-translational modification activity. The procedure used for the preparation of Neurospora cell-free extracts should be readily applicable to the other filamentous fungi.

Cell-Free System↗
PubMed1978

Current-voltage relationships for the plasma membrane and its principal electrogenic pump in Neurospora crassa: I. Steady-state conditions.

The nonlinear membrane current-voltage relationship (I-V curve) for intact hyphae of Neurospora crassa has been determined by means of a 3-electrode voltage-clamp technique, plus "quasi-linear" cable theory. Under normal conditions of growth and respiration, the membrane I-V curve is best described as a parabolic segment convex in the direction of depolarizing current. At the average resting potential of - 174 mV, the membrane conductance is approximately 190 micronhos/cm2; conductance increase to approximately 240 micronhos/cm2 at -300 mV, and decreases to approximately 130 micronhos/cm2 at 0 mV. Irreversible membrane breakdown occurs at potentials beyond this range. Inhibition of the primary electrogenic pump in Neurospora by ATP withdrawal (with 1 mM KCN) depolarizes the membrane to the range of -40 to -70 mV and reduces the slope of the I-V curve by a fixed scaling factor of approximately 0.8. For wild-type Neurospora, compared under control conditions and during steady-state inhibition by cyanide, the I-V difference curve--presumed to define the current-voltage curve for the electrogenic pump--is a saturation function with maximal current of approximately 20 muA/cm2, a half saturation potential near -300 mV, and a projected reversal potential of ca. -400 mV. This value is close to the maximal free energy available to the pump from ATP hydrolysis, so that pump stoichiometry must be close to 1 H+ extruded:1 ATP split. The time-courses of change in membrane potential and resistance with cyanide are compatible with the steady-state I-V curves, under the assumption the cyanide has no major effects other than ATP withdrawal. Other inhibitors, uncouplers, and lowered temperature all have more complicated effects. The detailed temporal analysis of voltage-clamp data showed three time-constants in the clamping currents: one of 10 msec, for charging the membrane capacitance (0.9 muF/cm/2); a second of 50-75 msec; and a third of 20-30 sec, perhaps representing changes of intracellular composition.

Biological Transport, Active↗
PubMed1975

Oscillations of an electrogenic pump in the plasma membrane of Neurospora.

The presence of the poky mutation in Neurospora crassa produces mitochondria which are defective in cytochromes b and aa3 but which compensate by means of an alternate, cyanide-insensitive oxidase. As previously reported (Slayman, Rees, Orchard & Slayman, J. Biol. Chem., 250:396, 1975) cyanide blockade of the poky strain carrying the partial suppressor f results in a metabolic downshift of only 56%, compared with a downshift of 98% in wild-type Neurospora; the downshift is accompanied by exponential decay of ATP in the wild type, but by an undershoot and monotonic recovery of ATP in poky f. Whereas the membrane potential declines with ATP in wild-type Neurospora, it oscillates near the resting level (ca. -- 185 mV) in poky f. Oscillations begin with a depolarizing swing of 30--100 mV, followed by slight hyperpolarization, then by 2--4 damped cycles having a frequency near 1/min. Similar oscillations arise with antimycin, salicyl hydroxamic acid, and several uncoupling agents, and depend on partial maintenance of respiration through either the defective cytochrome chain or the alternate oxidase. Small oscillations (maximally +/- 30% of the control value) in membrane conductance also occur, roughly in phase with the oscillations of membrane potential. The amplitude of these, in comparison with the nonlinearity of the normal current-voltage relationship for the membrane, strongly suggests that they arise as a secondary consequence of the voltage changes. Therefore, since it has previously been argued (Slayman, Long & Lu, J. Membrane Biol. 14:305, 1973) that most of the resting membrane potential in the organism arises from active extrusion of H+ ions, the simolest interpretation of the cyanide-induced voltage oscillations is that current through the H+ pump is modulated cyclically. The ultimate mechanism for this modulation is unresolved, but could plausible involve a metabolic feedback system, oscillations of intracellular pH, or both. In many respects the observed voltage oscillations resemble the well-known oscillations of mitochondrial H+ flux which are produced by sudden metabolic shifts.

Adenosine Triphosphate↗
PubMed1999

Transfer of Neurospora kalilo plasmids among species and strains by introgression.

There are four different variants of the kalilo "family" of linear mitochondrial plasmids. This family is found in several heterothallic species and one pseudohomothallic species of Neurospora, as well as in one homothallic species of Gelasinospora. The mode of dispersal of these plasmids is not known. Horizontal transmission has proved difficult to demonstrate. Another possibility is transfer by introgression, and this is modelled in the present paper. We have used introgression and subsequent heterokaryosis to successfully transfer the LA-kalilo plasmid from a Haitian strain of Neurospora crassa to the standard Oak Ridge N. crassa background, the LA-kalilo plasmid from the pseudohomothallic Neurospora tetrasperma to N. crassa, and the kalilo plasmid from N. crassa to N. tetrasperma. Thus, introgression is shown to be a possible avenue of dispersal between species. The recipient strains were all senescent but the mechanism of this senescence is not known. It could be caused by the plasmids, but if so the mechanism is novel since plasmid/mtDNA junction fragments of the type found in the standard mode of mtDNA insertion could not be detected. However, mtDNA changes were observed in the senescent recipients.

Base Sequence↗
PubMed1981

Effects of temperature acclimation on Neurospora phospholipids. Fatty acid desaturation appears to be a key element in modifying phospholipid fluid properties.

Experiments were conducted on the effect of growth temperature on phospholipids of Neurospora. Strains grown at high (37 degrees C) and low (15 degrees C) temperatures show large differences in the proportions of phospholipid fatty acid alpha-linolenate (18 : 3) which can vary by 10-fold over this temperature range. Changes in the phospholipid base composition are less dramatic; the most significant is an increase in phosphatidylethanolamines at low temperatures accompanied by a concomitant decrease in phosphatidylcholine. It appears that phospholipid fatty acid desaturation is closely regulated with respect to growth temperature. Over the 37 to 15 degrees C growth temperature range there appear to be at least two desaturase systems in Neurospora which are under different controls. Production of 18 : 1 and 18 : 2 species appears to occur at high levels over the entire temperature range, whereas the production of 18 : 3 seems to be inversely related to growth temperature. Shifting 37 degrees C-acclimated cultures to 15 degrees C produces a growth lag period of approximately 3 h, during which the level of 18 : 3 increases markedly. Differential scanning calorimetry of phospholipids from 37 degrees C cells shows a phase transition at -22 degrees C while lipids from 15 degrees C cultures exhibit a phase transition with reduced enthalpy at about -41 degrees C. The data are consistent with the idea that phospholipid composition in Neurospora is under strict control and suggest that membrane fluidity is regulated with respect to growth temperature through changes in membrane lipid composition.

Acclimatization↗
PubMed1980

3-Amino-1,2,4-triazole is an inhibitor of protein synthesis on mitoribosomes in Neurospora crassa.

The effects of the herbicide, 3-amino-1,2,4-triazole, an inhibitor of heme synthesis in rat liver, have been examined in the mold Neurospora crassa. The drug is a potent inhibitor of the growth of the mold and produces biochemical changes identical to those produced by chloramphenicol. 3-Amino-1,2,4-triazole, like chloramphenicol, is a direct and specific inhibitor of protein synthesis on mitoribosomes. A decrease in the levels of mitochondrial proteins which are completely or partly made on mitoribosomes and an accumulation in the levels of mitochondrial proteins of cytosolic origin have been observed. Both drugs depress porphyrin and heme levels, but there is actually an elevation in the levels of delta-aminolevulinate dehydratase, the rate-limiting enzyme of the heme-biosynthetic pathway in Neurospora crassa. In liver the enzyme is present in non-limiting amounts and the levels are depressed under conditions of 3-amino-1,2,4-triazole treatment. In Neurospora crassa the "derepression" of delta-aminolevulinate dehydratase under conditions of 3-amino-1,2,4-triazole or chloramphenicol treatment is only partial because the drugs inhibit protein synthesis on mitoribosomes. It is concluded that an optimal rate of protein synthesis on mitoribosomes is necessary to maintain an adequate rate of heme synthesis.

Amitrole↗
PubMed1981

Mutagen sensitivities and mutator effects of MMS-sensitive mutants in Neurospora.

7 mus (mutagen-sensitive) mutants of Neurospora crassa, which are more sensitive to the toxic effects of MMS (methyl methanesulfonate) than wild-type, were investigated for cross-sensitivities to other mutagens and inhibitors. These mutants have recently been mapped in 5 new genes, mus-7 to mus-11, and mutant alleles from each gene were checked for their effects on mutation frequencies. It was found that mutants in 3 of these 5 genes showed radiation-induced mutation frequencies similar to wild-type. These included 2 alleles of the gene mus-10, which were cross-sensitive only to UV and were the only mutants that produced some viable ascospores in homozygous crosses. The mutant of the second gene, mus-8, was especially sensitive to UV and mitomycin C and produced slightly reduced frequencies of spontaneous mutation. In contrast, the mutant of the third gene, mus-7, was not UV-sensitive but showed some cross-sensitivity to X-rays; mus-7 was highly sensitive to MMS and also to histidine, which inhibits various repair-defective mutants at concentrations well below those that reduce wild-type growth. None of these mus resemble mutants previously found in Neurospora, nor do they conform clearly to mutant types identified in E. coli or yeast. On the other hand mutants in 2 further genes, mus-11, and especially 2 alleles of mus-9, are very similar to uvs-3 of Neurospora and generally resemble mutants that are considered to be defective in "error-prone" repair. They were UV- as well as X-ray-sensitive, and showed strong spontaneous mutator effects but almost no increase in recessive lethal frequencies in heterokaryons after UV-treatments.

Deoxyribonucleases↗