rII Mutations Research Articles

Properties of Bacteriophage T4 Mutants Defective in Gene 30 (Deoxyribonucleic Acid Ligase) and the rII Gene

In Escherichia coli K-12 strains infected with phage T4 which is defective in gene 30 [deoxyribonucleic acid (DNA) ligase] and in the rII gene (product unknown), near normal levels of DNA and viable phage were produced. Growth of such T4 ligase-rII double mutants was less efficient in E. coli B strains which show the "rapidlysis" phenotype of rII mutations. In pulse-chase experiments coupled with temperature shifts and with inhibition of DNA synthesis, it was observed that DNA synthesized by gene 30-defective phage is more susceptible to breakdown in vivo when the phage is carrying a wild-type rII gene. Breakdown was delayed or inhibited by continued DNA synthesis. Mutations of the rII gene decreased but did not completely abolish the breakdown. T4 ligase-rII double mutants had normal sensitivity to ultraviolet irradiation.

Suppression of T4D ligase mutations by rIIa and rIIb mutations.

The introduction of rII mutations into polynucleotide ligase amber mutants (gene 30) of T4D bacteriophage results in the restoration of phage growth in the nonpermissive host E. coli B. When cells are mixedly infected with rII(+) -ligase(-) and rII-ligase(-) phage, growth is reduced, indicating that the rII mutations are recessive to the rII(+) alleles. Infection with the rII-ligase(-) double mutants results in nearly complete restoration of phage DNA synthesis and prevents the extensive degradation of parental phage DNA observed after infection with ligase(-) single mutants. Similar results are observed when cells are infected with ligase(-) mutants and chloramphenicol is added five minutes post infection.

Mutagenesis with light and proflavine in phage T4. II. Properties of the mutants.

In summary,rII mutations induced by exposure of T4 phage particles to either visible light or proflavine are acridine revertible. In both cases mutation occurs without inactivation. TherII mutations induced by the photodynamic action of proflavine on T4 phage particles are equally divided between the acridine revertible and base analogue revertible classes. It is proposed that photodynamic action induces base analogue mutations and that the acridine revertible category arises from the separate effects of light and proflavine.

On the expression of the rII mutation of T-even bacteriophages in Escherichia coli strain B

On the expression of the rII mutation of T-even bacteriophages in Escherichia coli strain B

AMBIVALENT rII MUTANTS OF PHAGE T4

The rII mutants of phage T4 differ from the standard type in being inactive on strains of Escherichia coli lysogenic for phage X. While the mutants attach to the cells and inject their DNA, progeny fail to appear. In this paper it is shown that one or another subset of the rII mutants can become active as a result of modification of the host, either by mutation or by the action of 5-fluorouracil. The effects are characterized by extreme specificity, applying only to certain rII mutations at certain points within the two rII cistrons. The phenomenon resembles what has been called, in many other systems, allele-specific suppression [1], in which a mutation outside a genetic region controlling a particular function suppresses the effects of some of the mutations within the region. An advantage of the phage system is that a given genetic message, in the form of a phage mutant, can be readily inserted into different hosts. The stimulus for the present investigation derives from the possibility that modifications of the host affecting the expression of specific phage mutations might be a key to the detection of alterations in the components of the cellular system for translating genetic information.

DNA synthesized in Escherichia coli K12 (lambda) after infection with an rII mutant of bacteriophage T4.

Abstract Deoxyribonucleic acid (DNA) synthesized in Escherichia coli K12 (λ) after abortive infection with rII mutants of phage T 4 was found to contain 5-hydroxymethylcytosine without any cytosine, as characteristic of phage DNA. It appears that physiological defect associated with the rII mutation is not a failure to form deoxycytidylate hydroxymethylase.

Physiological effects of rII mutations in bacteriophage T4.

Abstract The rII mutants of coliphage T4 are unable to produce progeny in host cells lysogenic for phage λ, if the infected cells are incubated in a medium containing a low concentration of Mg ++ ions. If a high Mg ++ concentration (0.05 M ) is provided, a normal yield of phage is obtained. In the low Mg ++ medium, phage development proceeds normally during the first 10 minutes after infection, as evidenced by the appearance of various phage-specific activities; also, deoxyribonucleic acid (DNA) and protein are synthesized at the normal rate during this period. Phage development, including DNA and protein syntheses, comes to an abrupt halt after 10 minutes, but can be restored by the addition of Mg ++ to the medium. Mg ++ is not effective in promoting phage development if aerobic metabolism is blocked.