Suppression of dual-effect mutants of the L-ribulokinase structural gene of Escherichia coli B/r

1971 ◽  
Vol 17 (8) ◽  
pp. 1105-1114
Author(s):  
Morad Abou-Sabe
Keyword(s):  
Enzyme Level ◽  
The Other ◽  
Wild Type ◽  
Dual Effect ◽  
Wild Type Level ◽  
Suppressor Mutations ◽  
Extragenic Suppressors ◽  
Escherichia Coli B ◽  
Distinct Increase ◽  
Arabinose Isomerase

A number of extragenic suppressors for two-dual effect, polarity, and hyperinducible L-ribulokinaseless mutants were isolated and enzymatically characterized. The effect of the suppressors on L-arabinose isomerase and L-ribulokinase enzyme activities was tested using a variety of arar suppressor-carrying strains. The effect of these suppressor mutations on T4 amber and ocher mutants was also studied. Results show that low-dual-effect, i.e. polarity, araB− suppressor-carrying strains invariably have a distinct increase in the L-arabinose isomerase enzyme level, above the wild-type level, irrespective of the restoration of the L-ribulokinase enzyme activity. High-dual-effect, hyperinducible, suppressed mutants, on the other hand, were not significantly altered in their L-arabinose isomerase enzyme level. It is also found that four different T4 amber mutants were suppressible by all tested suppressor-carrying strains, while T4 ocher mutants were not. It is concluded that the suppressor mutations studied are amber-like suppressors acting at the translation level, and that both polarity mutant araB68 and hyperinducible mutant araBA87 are nonsense mutants. The phenomenon of hyperinducibility is also discussed.

scholarly journals Differential Suppression of priA2::kan Phenotypes in Escherichia coli K-12 by Mutations in priA, lexA, and dnaC

Genetics ◽  
1996 ◽  
Vol 143 (1) ◽  
pp. 5-13 ◽  
Author(s):  
Steven J Sandler ◽  
Hardeep S Samra ◽  
Alvin J Clark
Keyword(s):  
Escherichia Coli ◽  
Dna Replication ◽  
Mutant Allele ◽  
Wild Type ◽  
Suppressor Mutations ◽  
Dnab Helicase ◽  
K 12 ◽  
Extragenic Suppressors ◽  
Assembly Activity

Abstract First identified as an essential component of the ϕX174 in vitro DNA replication system, PriA has ATPase, helicase, translocase, and primosome-assembly activities. priA1::kan strains of Escherichia coli are sensitive to UV irradiation, deficient in homologous recombination following transduction, and filamentous. priA2::kan strains have eightfold higher levels of uninduced SOS expression than wild type. We show that (1) priA1::kan strains have eightfold higher levels of uninduced SOS expression, (2) priA2::kan strains are UVS and Rec−, (3) lexA3 suppresses the high basal levels of SOS expression of a priA2::kan strain, and (4) plasmid-encoded priA300 (K230R), a mutant allele retaining only the primosome-assembly activity of priA+, restores both UVR and Rec+ phenotypes to a priA2::kan strain. Finally, we have isolated 17 independent UVR Rec+ revertants of priA2::kan strains that carry extragenic suppressors. All 17 map in the C-terminal half of the dnaC gene. DnaC loads the DnaB helicase onto DNA as a prelude for primosome assembly and DNA replication. We conclude that priA's primosome-assembly activity is essential for DNA repair and recombination and that the dnaC suppressor mutations allow these processes to occur in the absence of priA.

Suppressor mutations for crs mutants of Bacillus subtilis

1985 ◽  
Vol 31 (5) ◽  
pp. 429-435 ◽  
Author(s):  
D. Sun ◽  
I. Takahashi
Keyword(s):  
Alkaline Phosphatase ◽  
Bacillus Subtilis ◽  
Resistance Gene ◽  
Resistance Mutation ◽  
Suppressor Mutation ◽  
Wild Type ◽  
Erythromycin Resistance ◽  
Wild Type Level ◽  
Suppressor Mutations ◽  
Metabolic Activities

Mutants of Bacillus subtilis which carried suppressor mutations for catabolite-resistance gene crsA47 were isolated from methylmethanesulfonate-treated cultures of GLU-47 (crsA47). The suppressor mutation, sca19, suppressed resistance of crsA47 mutant to glucose and other inhibitors of sporulation. Moreover, the suppressor mutation could restore the rate of growth and the level of IMP dehydrogenase and alkaline phosphatase of crsA47 mutant to the wild-type level. The sca19 mutation was also able to suppress catabolite resistance of other crs mutants. The map position of the sea19 mutation indicated that this mutation was an intergenic suppressor for the crs mutants. It was also found that an erythromycin-resistance mutation, ery1, could suppress the catabolite resistance of some of the crs mutants. Our results were discussed in relation to the importance of a proper state of metabolic activities and membrane functions during the initiation of sporulation.

scholarly journals RECESSIVE LETHAL AMBER SUPPRESSORS IN YEAST

Genetics ◽  
1975 ◽  
Vol 79 (4) ◽  
pp. 551-560
Author(s):  
Marjorie C Brandriss ◽  
Larry Soll ◽  
David Botstein
Keyword(s):  
Saccharomyces Cerevisiae ◽  
The Other ◽  
Wild Type ◽  
Diploid Strain ◽  
Recessive Lethal ◽  
Suppressor Mutations ◽  
Amber Suppressor ◽  
Chromosome Iii

ABSTRACT Recessive lethal amber suppressor mutations have been isolated in a diploid strain of Saccharomyces cerevisiae. Diploids carrying these suppressors upon sporulation yield asci with only two live spores, both lacking the suppressor. At least two classes of recessive lethal suppressors exist. Aneuploid strains carrying one wild type and one suppressor locus have been isolated and used in mapping studies; one suppressor maps on chromosome III, the other does not.

ISOLEMENT ET CHARACTÉRISATION DE MUTANTS SENSIBLES OU RÉSISTANTS À L'OZONE CHEZESCHERICHIA COLIB

1982 ◽  
Vol 24 (5) ◽  
pp. 593-600 ◽  
Author(s):  
L. Poliquin ◽  
C. Hamelin ◽  
Y. S. Chung
Keyword(s):  
Escherichia Coli ◽  
Single Gene ◽  
Dna Lesions ◽  
The Other ◽  
Wild Type ◽  
Ozone Sensitivity ◽  
Other Hand ◽  
Radio Sensitivity ◽  
Escherichia Coli B

Escherichia coli B strains, either more sensitive or resistant to ozone than wild-type (OZsor OZr), were obtained after mutagenesis. OZsstrains carrying a mutation in ozrA or orzB, two genes located on both sides of malB, appeared as phenotypically different with regards to radio-sensitivity and cellular filamentation. OZrstrains, on the other hand, probably carry an allele of ozrA but were radioresistant and divided normally even with induction. A single gene (ozrA) thus seems to determine three levels of sensitivity to ozone, sensitivity to radiation and cellular filamentation in this organism. The possible involvement of a specific endonuclease in the repair of ozone-induced DNA lesions is considered.

scholarly journals Rvs161p and Sphingolipids Are Required for Actin Repolarization following Salt Stress

2002 ◽  
Vol 1 (6) ◽  
pp. 1021-1031 ◽  
Author(s):  
Axelle Balguerie ◽  
Michel Bagnat ◽  
Marc Bonneu ◽  
Michel Aigle ◽  
Annick M. Breton
Keyword(s):  
Lipid Rafts ◽  
Nacl Stress ◽  
Salt Sensitivity ◽  
The Other ◽  
Salt Medium ◽  
Wild Type ◽  
Wild Type Level ◽  
Bud Emergence ◽  
Suppressor Mutants ◽  
Sphingolipid Biosynthesis

ABSTRACT In Saccharomyces cerevisiae, the actin cytoskeleton is depolarized by NaCl stress. In this study, the response was maximal after 30 min, and then actin patches repolarized. Rvs161p was required for actin repolarization because the rvs161Δ mutant did not repolarize actin patches after growth in a salt medium. Mutations suppressing the rvs161Δ-related salt sensitivity all occurred in genes required for sphingolipid biosynthesis: FEN1, SUR4, SUR2, SUR1, and IPT1. These suppressors also suppressed act1-1-related salt sensitivity and the defect in actin repolarization of the rvs161Δ mutant, providing a link between sphingolipids and actin polarization. Indeed, deletion of the suppressor genes suppressed the rvs161Δ defect in actin repolarization in two ways: either actin was not depolarized at the wild-type level in a set of suppressor mutants, or actin was repolarized in the absence of Rvs161p in the other suppressor mutants. Rvs161p was localized as cortical patches that concentrated at polarization sites, i.e., bud emergence and septa, and was found to be associated with lipid rafts. An important link between sphingolipids and actin polarization is that Rvs161p was required for actin repolarization and was found to be located in lipid rafts.

Normal Synaptonemal Complex and Abnormal Recombination Nodules in Two Alleles of the Drosophila Meiotic Mutant mei-W68

Genetics ◽  
2003 ◽  
Vol 163 (4) ◽  
pp. 1337-1356 ◽  
Author(s):  
Adelaide T C Carpenter
Keyword(s):  
Electron Microscopy ◽  
Synaptonemal Complex ◽  
High Frequency ◽  
Serial Section ◽  
The Other ◽  
Wild Type ◽  
Recombination Nodules ◽  
Section Electron ◽  
Serial Section Electron Microscopy ◽  
Section Electron Microscopy

Abstract The meiotic phenotypes of two mutant alleles of the mei-W68 gene, 1 and L1, were studied by genetics and by serial-section electron microscopy. Despite no or reduced exchange, both mutant alleles have normal synaptonemal complex. However, neither has any early recombination nodules; instead, both exhibit high numbers of very long (up to 2 μm) structures here named “noodles.” These are hypothesized to be formed by the unchecked extension of identical but much shorter structures ephemerally seen in wild type, which may be precursors of early recombination nodules. Although the mei-W68L1 allele is identical to the mei-W681 allele in both the absence of early recombination nodules and a high frequency of noodles (i.e., it is amorphic for the noodle phene), it is hypomorphic in its effects on exchange and late recombination nodules. The differential effects of this allele on early and late recombination nodules are consistent with the hypothesis that Drosophila females have two separate recombination pathways—one for simple gene conversion, the other for exchange.

scholarly journals A Screen for Genes That Function in Abscisic Acid Signaling in Arabidopsis thaliana

Genetics ◽  
2002 ◽  
Vol 161 (3) ◽  
pp. 1247-1255 ◽  
Author(s):  
Eiji Nambara ◽  
Masaharu Suzuki ◽  
Suzanne Abrams ◽  
Donald R McCarty ◽  
Yuji Kamiya ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Growth And Development ◽  
Plant Hormone ◽  
The Other ◽  
Aba Signaling ◽  
Wild Type ◽  
Plant Growth And Development ◽  
Diverse Range ◽  
Abscisic Acid Signaling ◽  
Aba Insensitive

Abstract The plant hormone abscisic acid (ABA) controls many aspects of plant growth and development under a diverse range of environmental conditions. To identify genes functioning in ABA signaling, we have carried out a screen for mutants that takes advantage of the ability of wild-type Arabidopsis seeds to respond to (−)-(R)-ABA, an enantiomer of the natural (+)-(S)-ABA. The premise of the screen was to identify mutations that preferentially alter their germination response in the presence of one stereoisomer vs. the other. Twenty-six mutants were identified and genetic analysis on 23 lines defines two new loci, designated CHOTTO1 and CHOTTO2, and a collection of new mutant alleles of the ABA-insensitive genes, ABI3, ABI4, and ABI5. The abi5 alleles are less sensitive to (+)-ABA than to (−)-ABA. In contrast, the abi3 alleles exhibit a variety of differences in response to the ABA isomers. Genetic and molecular analysis of these alleles suggests that the ABI3 transcription factor may perceive multiple ABA signals.

scholarly journals act Operon Control of Developmental Gene Expression in Myxococcus xanthus

2002 ◽  
Vol 184 (4) ◽  
pp. 1172-1179 ◽  
Author(s):  
Thomas M. A. Gronewold ◽  
Dale Kaiser
Keyword(s):  
Fruiting Body ◽  
Myxococcus Xanthus ◽  
The Other ◽  
Loss Of Function ◽  
Wild Type ◽  
Developmental Gene ◽  
Developmental Gene Expression ◽  
Mutant Strains ◽  
Genes Encoding ◽  
Signal Production

ABSTRACT Cell-bound C-signal guides the building of a fruiting body and triggers the differentiation of myxospores. Earlier work has shown that transcription of the csgA gene, which encodes the C-signal, is directed by four genes of the act operon. To see how expression of the genes encoding components of the aggregation and sporulation processes depends on C-signaling, mutants with loss-of-function mutations in each of the act genes were investigated. These mutations were found to have no effect on genes that are normally expressed up to 3 h into development and are C-signal independent. Neither the time of first expression nor the rate of expression increase was changed in actA, actB, actC, or actD mutant strains. Also, there was no effect on A-signal production, which normally starts before 3 h. By contrast, the null act mutants have striking defects in C-signal production. These mutations changed the expression of four gene reporters that are related to aggregation and sporulation and are expressed at 6 h or later in development. The actA and actB null mutations substantially decreased the expression of all these reporters. The other act null mutations caused either premature expression to wild-type levels (actC) or delayed expression (actD), which ultimately rose to wild-type levels. The pattern of effects on these reporters shows how the C-signal differentially regulates the steps that together build a fruiting body and differentiate spores within it.

scholarly journals Prostacyclin-IP signaling and prostaglandin E2-EP2/EP4 signaling both mediate joint inflammation in mouse collagen-induced arthritis

2006 ◽  
Vol 203 (2) ◽  
pp. 325-335 ◽  
Author(s):  
Tetsuya Honda ◽  
Eri Segi-Nishida ◽  
Yoshiki Miyachi ◽  
Shuh Narumiya
Keyword(s):  
Rheumatoid Arthritis ◽  
Synovial Fluid ◽  
Joint Inflammation ◽  
Synovial Fibroblasts ◽  
The Other ◽  
Receptor Subtype ◽  
Significant Suppression ◽  
Wild Type ◽  
Collagen Induced Arthritis

Prostaglandin (PG)I2 (prostacyclin [PGI]) and PGE2 are abundantly present in the synovial fluid of rheumatoid arthritis (RA) patients. Although the role of PGE2 in RA has been well studied, how much PGI2 contributes to RA is little known. To examine this issue, we backcrossed mice lacking the PGI receptor (IP) to the DBA/1J strain and subjected them to collagen-induced arthritis (CIA). IP-deficient (IP−/−) mice exhibited significant reduction in arthritic scores compared with wild-type (WT) mice, despite anti-collagen antibody production and complement activation similar to WT mice. IP−/− mice also showed significant reduction in contents of proinflammatory cytokines, such as interleukin (IL)-6 in arthritic paws. Consistently, the addition of an IP agonist to cultured synovial fibroblasts significantly enhanced IL-6 production and induced expression of other arthritis-related genes. On the other hand, loss or inhibition of each PGE receptor subtype alone did not affect elicitation of inflammation in CIA. However, a partial but significant suppression of CIA was achieved by the combined inhibition of EP2 and EP4. Our results show significant roles of both PGI2-IP and PGE2-EP2/EP4 signaling in the development of CIA, and suggest that inhibition of PGE2 synthesis alone may not be sufficient for suppression of RA symptoms.

scholarly journals Suppressor Mutations Bypass the Requirement of fluG for Asexual Sporulation and Sterigmatocystin Production in Aspergillus nidulans

Genetics ◽  
2003 ◽  
Vol 165 (3) ◽  
pp. 1083-1093
Author(s):  
Jeong-Ah Seo ◽  
Yajun Guan ◽  
Jae-Hyuk Yu
Keyword(s):  
Aspergillus Nidulans ◽  
Molecular Mechanisms ◽  
Dominant Negative ◽  
Wild Type ◽  
Dominant Mutation ◽  
Site Mutation ◽  
Asexual Sporulation ◽  
Dominant Negative Mutation ◽  
Suppressor Mutations ◽  
Early Developmental

Abstract Asexual sporulation (conidiation) in the filamentous fungus Aspergillus nidulans requires the early developmental activator fluG. Loss of fluG results in the blockage of both conidiation and production of the mycotoxin sterigmatocystin (ST). To investigate molecular mechanisms of fluG-dependent developmental activation, 40 suppressors of fluG (SFGs) that conidiate without fluG have been isolated and characterized. Genetic analyses showed that an individual suppression is caused by a single second-site mutation, and that all sfg mutations but one are recessive. Pairwise meiotic crosses grouped mutations to four loci, 31 of them to sfgA, 6 of them to sfgB, and 1 each to sfgC and sfgD, respectively. The only dominant mutation, sfgA38, also mapped to the sfgA locus, suggesting a dominant negative mutation. Thirteen sfgA and 1 sfgC mutants elaborated conidiophores in liquid submerged culture, indicating that loss of either of these gene functions not only bypasses fluG function but also results in hyperactive conidiation. While sfg mutants show varying levels of restored conidiation, all recovered the ability to produce ST at near wild-type levels. The fact that at least four loci are defined by recessive sfg mutations indicates that multiple genes negatively regulate conidiation downstream of fluG and that the activity of fluG is required to remove such repressive effects.

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