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I Tessman

Publications and source records attributed to I Tessman.

At least 37 records · Page 2Linked to original sources
PubMed1991

Excision and transposition of Tn5 as an SOS activity in Escherichia coli.

Excision and transposition of the Tn5 element in Escherichia coli ordinarily appear to occur by recA-independent mechanisms. However, recA(Prtc) genes, which encode RecA proteins that are constitutively activated to the protease state, greatly enhanced excision and transposition; both events appeared to occur concomitantly and without destruction of the donor DNA. The recombinase function of the RecA protein was not required. Transposition was accompanied by partial, and occasionally full, restoration of the functional integrity of the gene vacated by the excised Tn5. The stimulation of transposition was inhibited by an uncleavable LexA protein and was strongly enhanced by an additional role of the RecA(Prtc) protein besides its mediation of LexA cleavage. To account for the enhanced transposition, we suggest that (i) there may be a LexA binding site within the promoter for the IS50 transposase, (ii) activated RecA may cleave the IS50 transposition inhibitor, and (iii) the transposase may be formed by RecA cleavage of a precursor molecule.

Bacterial Proteins↗
PubMed1991

LexA protein of Escherichia coli represses expression of the Tn5 transposase gene.

The LexA protein of Escherichia coli represses expression of a variety of genes that, by definition, constitute the SOS regulon. Genetic evidence suggests that Tn5 transposition is also regulated by the product of the lexA gene (C.-T. Kuan, S.-K. Liu, and I. Tessman, Genetics 128:45-57, 1991). We now show that the LexA protein represses expression of the tnp gene, located in the IS50R component of Tn5, which encodes a transposase, and that LexA does not repress expression of the IS50R inh gene, which encodes an inhibitor of transposition. Elimination of LexA resulted in increased expression of the tnp gene by a factor of 2.7 +/- 0.4, as indicated by the activity of a lacZ gene fused to the tnp gene. LexA protein retarded the electrophoretic movement of a 101-bp segment of IS50R DNA that contained a putative LexA protein-binding site in the tnp promoter; the interaction between the LexA repressor and the promoter region of the tnp gene appears to be relatively weak. These features show that the IS50R tnp gene is a member of the SOS regulon.

Bacterial Proteins↗
PubMed1990

Error-prone SOS repair can be error-free.

Most of the mutagenesis that accompanies the SOS repair of ultraviolet light-induced lesions in the single-stranded DNA of phage S13 is eliminated when the groES or the groEL gene of Escherichia coli is defective. Therefore, this SOS mutagenesis is not a necessary consequence of what is commonly called error-prone repair, but is additionally imposed on the repair system by the GroE heat shock proteins, which are responsible for the assembly of polypeptides into multimeric structures.

Bacterial Proteins↗
PubMed1990

Mutagenesis by proximity to the recA gene of Escherichia coli.

Escherichia coli recA (Prtc) strains, which produce protease constitutive RecA proteins in the absence of DNA-damaging treatments, display an increased frequency of spontaneous mutations. These mutations occurred preferentially in the neighborhood of the recA gene. This cis-like mutagenic effect was observed in the recA, rexAB, phoE and bio genes. The localized mutagenesis can be explained by the ease with which RecA(Prtc) proteins are activated to the protease state, which implies that there should be a relatively high concentration of activated RecA protein near the recA gene, where the protein is synthesized. The unusually high frequency of mutation in the recA gene is a novel example of an overactive gene preferentially turning itself down by mutation.

Chromosome Mapping↗
PubMed1990

groE genes affect SOS repair in Escherichia coli.

Repair of UV-irradiated bacteriophage in Escherichia coli by Weigle reactivation requires functional recA+ and umuD+C+ genes. When the cells were UV irradiated, the groE heat shock gene products, GroES and GroEL, were needed for at least 50% of the Weigle reactivation of the single-stranded DNA phage S13. Because of repression of the umuDC and recA genes, Weigle reactivation is normally blocked by the lexA3(Ind-) mutation (which creates a noncleavable LexA protein), but it was restored by a combination of a high-copy-number umuD+C+ plasmid and a UV dose that increases groE expression. Maximal reactivation was achieved by elevated amounts of the Umu proteins, which was accomplished in part by UV-induced expression of the groE genes. By increasing the number of copies of the umuD+C+ genes, up to 50% of the normal amount of reactivation of S13 was achieved in an unirradiated recA+ host.

Coliphages↗
PubMed1990

SOS repair can be about as effective for single-stranded DNA as for double-stranded DNA and even more so.

As ordinarily measured, the SOS repair of damaged DNA by Weigle reactivation appears to be more effective for double-stranded (ds) than for single-stranded (ss) DNA bacteriophages. A complicating feature, which is usually not considered, is the possibility of DNA-protein cross-linking of ssDNA to the viral capsid, which would conceivably be an extraneous source of nonreactivable lesions. This idea is supported in studies of phage S13 by the observation that photoreactivation more than doubles when naked ssDNA is substituted for encapsidated ssDNA as the UV target. The same effect was observed for Weigle reactivation; there was little, if any, difference in the reactivation of ssDNA and dsDNA when naked DNA was irradiated. Moreover, in a uvrA mutant, ssDNA actually had the advantage; Weigle reactivation was then more than twice as effective for ssDNA as for dsDNA. It is also shown that when a suitable measure of Weigle mutagenesis is used, there is no convincing evidence that dsDNA is mutagenized more effectively than ssDNA.

Bacteriophage lambda↗
PubMed1989

Levels of DNA topoisomerases, single-stranded-DNA-binding protein, and DNA polymerase I in rho+ and rho-15 strains of Escherichia coli.

The Escherichia coli rho-15 mutant, which is highly defective in transcription termination, was examined to see whether its reduced DNA superhelicity could be explained by altered expression of proteins that may affect DNA structure. Levels of DNA gyrase and topoisomerase I were normal; levels of single-stranded-DNA-binding protein, DNA polymerase I, and a protein tentatively identified as Lon were significantly altered.

DNA Polymerase I↗
PubMed1988

Activation of protease-constitutive recA proteins of Escherichia coli by all of the common nucleoside triphosphates.

To understand why the RecA proteins of the protease-constitutive recA1202 and recA1211 mutants show very high protease activities in vivo without the usual need for DNA damage (E. S. Tessman and P. Peterson, J. Bacteriol. 163:677-687, 1985), we examined the activation of the mutant proteins by nucleoside triphosphates (NTPs) in vitro. In vivo, the mutant protease activities are resistant to inhibition by cytidine plus guanosine (C + G) in the growth medium, in contrast to the activities of weaker mutants, such as recA441, which are sensitive to C + G inhibition. We found that RecA1202 and RecA1211 proteins, in contrast to RecA+, can use natural NTPs other than ATP and dATP as cofactors in the cleavage of LexA repressor. The effectiveness of NTPs in promoting LexA cleavage by RecA1202 and RecA1211 proteins decreased in roughly the following order: dATP greater than ATP greater than UTP greater than ATP-gamma S greater than dCTP greater than CTP greater than dGTP greater than GTP greater than TTP. These mutant proteins showed higher affinities for ATP and single-stranded DNA and higher repressor cleavage activities than RecA+ protein. With the various effectors (single-stranded DNA or NTPs), the RecA1202 protein always showed more activity than RecA1211 in the cleavage of LexA repressor in vitro, which is consistent with the greater activity of the recA1202 mutant in vivo. The results explain, in part, why some recA mutants have unusually high constitutive RecA protease activity and why that activity is more or less resistant to C + G inhibition.

Adenosine Triphosphate↗
PubMed1988

Activation of protease-constitutive recA proteins of Escherichia coli by rRNA and tRNA.

The RecA proteins of the unusually strong protease-constitutive mutants recA1202 and recA1211 can use RNA in addition to single-stranded DNA (ssDNA) as a cofactor in the cleavage of the LexA repressor in vitro. In the presence of rRNA or tRNA, the effectiveness of these proteins decreased in the order RecA1202 greater than RecA1211 much greater than RecA+, which is also the order of their in vivo constitutive protease activities. The effectiveness of rRNA was comparable to that of ssDNA in the cleavage of the LexA repressor by either mutant protease. Although all the common nucleoside triphosphates can act as positive effectors for LexA cleavage by the two mutant proteins in the presence of ssDNA (W. B. Wang, M. Sassanfar, I. Tessman, J. W. Roberts, and E. S. Tessman, J. Bacteriol. 170:4816-4822, 1988), only dATP, ATP, and ATP-gamma-S were effective in the presence of RNA. Our results explain more fully why certain recA mutants have high constitutive protease activities in vivo.

Bacterial Proteins↗
PubMed1988

Regulation of DNA superhelicity by rpoB mutations that suppress defective Rho-mediated transcription termination in Escherichia coli.

The highly defective rho-15 mutant of Escherichia coli produces plasmid DNA that is 22% less negatively supercoiled than DNA from an isogenic wild-type strain (J. S. Fassler, G. F. Arnold, and I. Tessman, Mol. Gen. Genet. 204:424-429, 1986). We extended our measurements of plasmid superhelicity to additional rho mutants and to strains containing mutations that suppress rho transcription termination defects; the suppressor mutations were in the rpoB and the rho genes. The superhelicity of plasmid DNA was reduced by 11 and 10%, respectively, in the rho-702 and rho-201 mutants, both of which are less defective in Rho-mediated transcription termination than rho-15. Plasmid superhelicity was restored in all the suppressed rho mutants; in one rpoB mutant, plasmid DNA was even more negatively supercoiled than in rpoB+ cells, whether in a rho+ or rho mutant background. Suppression of rho mutants enabled them to maintain plasmids that could not be maintained in the mutants in the absence of the suppressor mutations. The results indicate that in addition to DNA gyrase, topoisomerase I, and Rho, RNA polymerase is also a determinant of DNA superhelicity, and its effect is modified by the Rho protein. We propose that Rho may increase the degree of DNA unwinding by the transcription complex, possibly at transcription termination sites.

DNA, Bacterial↗
PubMed1986

Reduced superhelicity of plasmid DNA produced by the rho-15 mutation in Escherichia coli.

The plasmid pJSF6, a derivative of pBR327, could be maintained at 30 degrees C in strains of Escherichia coli containing the strong rho mutation, rho-15. Plasmids extracted from rho-15 cells were always less negatively supercoiled than plasmids from rho+ cells. Transduction experiments designed to separate the rho gene from possible extragenic suppressors showed that the rho allele consistently determined the degree of plasmid superhelicity. Comparison of the superhelicity of plasmids extracted from the rho-15 and from a gyrB mutant showed that at 30 degrees C the negative supercoiling was reduced by the amounts delta Wrho = 4.0 +/- 0.3 and delta Wgyr = 6.0 +/- 0.3 turns; the effect of the rho-15 mutation on supercoiling was thus comparable to that of the gyrB mutation. A similar effect of the rho-15 mutation on the superhelicity of pBR329 was observed. The observation that the Rho protein has a role in determining DNA superhelicity (though not necessarily a direct role) provides a new point of view for studying the pleiotropic properties of rho mutants.

DNA Topoisomerases, Type II↗
PubMed1986

Roles of RecA protease and recombinase activities of Escherichia coli in spontaneous and UV-induced mutagenesis and in Weigle repair.

The RecA protein has a second, direct role in the mutagenesis of Escherichia coli and bacteriophage lambda in addition to its first, indirect role of inducing the SOS system by enhancing the proteolytic cleavage of the LexA repressor protein. The need for RecA protease and recombinase functions in the direct role was examined in cells containing split-phenotype RecA mutations, in the absence of LexA protein. Spontaneous mutation of E. coli (his----his+) required both the protease and recombinase activities. The mutation frequency increased with increasing RecA protease strength. In contrast, UV-induced mutation of E. coli required only the RecA protease activity. Weigle repair and mutation of UV-irradiated phage S13 required only RecA protease activity, and even weak activity was highly effective; RecA recombinase activity was not required. RecA+ protein inhibited RecA (Prtc [protease constitutive] Rec+) protein in effecting spontaneous mutation of E. coli. We discuss the nature of the direct role of the RecA protein in spontaneous mutation and in repair and mutagenesis of UV-damaged DNA and also the implications of our results for the theory that SOS-mutable cryptic lesions might be responsible for the enhanced spontaneous mutation in Prtc Rec+ strains.

Bacterial Proteins↗
PubMed1985

UV-induced mutagenesis of phage S13 can occur in the absence of the RecA and UmuC proteins of Escherichia coli.

The UV-induced mutagenesis of phage S13 that accompanies Weigle repair is known to require the products of the recA and umuDC genes, as does the UV-induced mutagenesis of the Escherichia coli chromosome. I found that UV-induced mutagenesis of phage S13 occurred in the absence of both the RecA and UmuC functions when the irradiated phage was photoreactivated. Furthermore, UV-induced phage mutations were produced in a recA- umuC- cell even without photoreactivation and in the absence of any other known UV repair mechanism, at a frequency 29% of that found after photoreactivation and 7% of that found after Weigle repair, implying that DNA synthesis can proceed past a dimer at an unexpectedly high frequency even when unaided by the UmuC-RecA SOS repair functions. The unaided DNA synthesis appears capable of producing mutations in the vicinity of a pyrimidine dimer; by aiding synthesis past a dimer, a repair mechanism may disclose a mutation without having any active role in producing it.

Bacterial Proteins↗
PubMed1985

Lethality of the double mutations rho rep and rho ssb in Escherichia coli.

The similarity of rho mutants to rep and ssb mutants in sensitivity to UV light and in recombination deficiency suggested that the function of the Rho protein might be related to that of Rep and Ssb. In support of that idea, we found that rho rep and rho ssb double mutants are either nonviable, or at best only marginally viable. Viability could be restored by suppressor mutations, one of which mapped either in the rho gene or close to its 5'-end. Rho may thus share a role with Rep and Ssb in replication and the structural maintenance of DNA; a multifunctional Rho protein could account for the diversity of the defects seen in rho mutants, some of which appear to have no relation to the defect in transcription termination.

Adenosine Triphosphatases↗
PubMed1982

Relative map location of the rep and rho genes of Escherichia coli.

The rep gene of Escherichia coli was mapped between ilvC and rho by three-factor P1 transductional crosses and also by complementation with a set of lambda transducing phages that contain known amounts of bacterial DNA linked to ilvC. The physical distance between ilvC and rep and between rep and rho were calculated with an accuracy of +/- 0.4 kilobase to be 0 less than or equal to ilvC-rep less than or equal to 3.4 kilobases and 2.0 less than or equal to rep-rho less than or equal to 6.0 kilobases. It was shown that rho-15 is Gro+ for phage ST-1. An ilv::Tn10 mutation was located in ilvY.

Bacterial Proteins↗
PubMed1981

Relation between UV suppression of polarity in phi X174 and UV sensitivity of rho mutants.

The suppression of polarity by UV irradiation was similar to the suppression by rho mutants. This was demonstrated for a polar nonsense mutant of phage phi X174. Treatment of the host for 30 min with 100 micrograms of the radiomimetic drug mitomycin C per ml was about as effective as 550 J of UV irradiation per m2 in relieving polarity. The shape of the UV survival curves for rho mutants could be linked to a proposed mechanism of UV relief of polarity. Host cell reactivation of phage lambda and W-reactivation of phage G4 were unaffected by rho mutations. UV suppression of polarity is independent of the Hcr- and RecA- phenotypes. An explanation for the UV sensitivity of rho mutants is provided, and several ways are considered in which UV irradiation may deplete cellular rho activity and thereby cause UV relief of polarity. We propose a novel theory that relates the UV inactivation of normal repair-proficient cells to a decrease in rho activity.

Bacteriophage phi X 174↗