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J M Crasemann

Publications and source records attributed to J M Crasemann.

9 recordsLinked to original sources
PubMed1982

Orientation of cohesive end site cos determines the active orientation of chi sequence in stimulating recA . recBC-mediated recombination in phage lambda lytic infections.

Sequence chi, 5'G-C-T-G-G-T-G-G, locally enhances homologous recombination by recA and recBC proteins of Escherichia coli. Previous work showed that, in phage lambda, chi is more active in one orientation (leftward) than in the other (rightward). Inverting cos, the sequence for the mature DNA ends of lambda, reverses this orientation dependence: the rightward chi becomes fully active, and the leftward chi becomes relatively inactive. We surmise that chi action in phage lambda is coupled with DNA packaging or injection.

Bacterial Proteins↗
PubMed1980

Generalized recombination: nucleotide sequence homology between Chi recombinational hotspots.

Chi sites stimulate generalized recombination catalyzed by the RecA-RecBC-dependent system of E. coli. This stimulation occurs over a region of several thousand base pairs surrounding the Chi site. These sites arise by mutation at four distinct loci in bacteriophage lambda. We report here the nucleotide sequence surrounding one of these loci, chi B, located between the xis and reda genes. Alteration of a single GC base pair, by deletion or by transversion to a CG base pair, creates the Chi recombinational hotspot chi + B. In a section of 30 bp, the chi + B sequence has 23 bp in common with the chi + C sequence determined previously. We presume that some part of this common sequence is the recognition sequence for a protein which acts at a rate-limiting step of generalized recombination.

Bacteriophage lambda↗
PubMed1980

Directionality and nonreciprocality of Chi-stimulated recombination in phage lambda.

Chi's are genetic elements that stimulate generalized recombination in their locale in phage lambda. All Chi's wherever located on lambda's chromosome, act asymmetrically in crosses blocked in DNA replication: (1) They stimulate exchange primarily to their left on the conventional lambda map, and (2) the stimulated exchange is frequently nonreciprocal, the recombinant carrying the Chi element being produced less often than the complementary product.

Bacteriophage lambda↗
PubMed1979

Chi.

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Alleles↗
PubMed1974

The distribution of crossovers along unreplicated lambda bacteriophage chromosomes.

The distribution of crossovers along unreplicated chromosomes of bacteriophage lambda has been examined by determining the density distributions and genotypes of particles in the progenies of crosses of density-labeled by ordinary parents in the presence of genetic blocks to replication. The Red and Rec systems combined produce crossovers primarily near the ends (especially the right end) of the chromosome. Removal of the generalized lambda recombination functions by red and gam mutations results in loss of these terminal crossovers; coupled with this loss is a disappearance of the differential dependence of recombination frequencies in terminal and central intervals on DNA synthesis. Removal of the bacterial system by a recA mutation results in severe depression of crossing over among unreplicated phage, with the few recombinants produced by the lambda system occurring near the right end.

Chromosome Mapping↗