A genetic switch in vitro: DNA inversion by Gin protein of phage Mu. 1984

R H Plasterk, and R Kanaar, and P van de Putte

Inversion of the G segment in the DNA of Escherichia coli phage Mu depends on the Mu Gin protein and alters the host range of the phage. The frequency of the inversion reaction is low both in the lysogenic state and during lytic growth. A sensitive assay was developed to detect low levels of G inversion: the E. coli lac operon was inserted within the invertible G segment in such a way that the lac operon was expressed only by G(-) clones. As a result Gin-catalyzed inversion from G(+) to G(-) can be monitored as a lactose-negative to lactose-utilizing switch. Using a crude extract from a Gin-overproducing strain and this assay plasmid, we could detect a low level of G inversion in vitro (1% in 30 min). The reaction depends on Mg2+ and a supercoiled substrate. Under optimized reaction conditions over 15% of the plasmids had the G segment inverted after incubation with Gin in vitro. The inversion was then visualized by agarose gel analysis of plasmid DNA digested by restriction endonucleases. The Gin protein retains its catalytic properties upon partial purification. The mechanism of this genetic switch can now be studied in vitro.

UI MeSH Term Description Entries
D007446 Chromosome Inversion An aberration in which a chromosomal segment is deleted and reinserted in the same place but turned 180 degrees from its original orientation, so that the gene sequence for the segment is reversed with respect to that of the rest of the chromosome. Inversion, Chromosome,Inversion, Chromosomal,Chromosomal Inversion,Chromosomal Inversions,Chromosome Inversions,Inversions, Chromosomal,Inversions, Chromosome
D008274 Magnesium A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D010583 Bacteriophage mu A temperate coliphage, in the genus Mu-like viruses, family MYOVIRIDAE, composed of a linear, double-stranded molecule of DNA, which is able to insert itself randomly at any point on the host chromosome. It frequently causes a mutation by interrupting the continuity of the bacterial OPERON at the site of insertion. Coliphage mu,Enterobacteria phage Mu,Phage mu,mu Phage,mu Phages
D010957 Plasmids Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS. Episomes,Episome,Plasmid
D011995 Recombination, Genetic Production of new arrangements of DNA by various mechanisms such as assortment and segregation, CROSSING OVER; GENE CONVERSION; GENETIC TRANSFORMATION; GENETIC CONJUGATION; GENETIC TRANSDUCTION; or mixed infection of viruses. Genetic Recombination,Recombination,Genetic Recombinations,Recombinations,Recombinations, Genetic
D004269 DNA, Bacterial Deoxyribonucleic acid that makes up the genetic material of bacteria. Bacterial DNA
D004278 DNA, Superhelical Circular duplex DNA isolated from viruses, bacteria and mitochondria in supercoiled or supertwisted form. This superhelical DNA is endowed with free energy. During transcription, the magnitude of RNA initiation is proportional to the DNA superhelicity. DNA, Supercoiled,DNA, Supertwisted,Supercoiled DNA,Superhelical DNA,Supertwisted DNA
D004279 DNA, Viral Deoxyribonucleic acid that makes up the genetic material of viruses. Viral DNA
D014764 Viral Proteins Proteins found in any species of virus. Gene Products, Viral,Viral Gene Products,Viral Gene Proteins,Viral Protein,Protein, Viral,Proteins, Viral

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