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Biomedical subjects

R Kahmann

Publications and source records attributed to R Kahmann.

89 records · Page 5Linked to original sources
PubMed1985

G inversion in bacteriophage Mu DNA is stimulated by a site within the invertase gene and a host factor.

The Gin function of bacteriophage Mu catalyzes inversion of the G DNA segment, thus switching the host range of Mu phage particles. This site-specific recombination event takes place between inverted repeat sequences (IR) that border the G segment. Sequences in the Mu beta region extending approximately from position 118 to 178 are essential for efficient inversion. In cis this region, termed sis, stimulates inversion about 15-fold. Neither the relative orientation of sis with respect to the IR sequences nor the distance to IR substantially influences the stimulatory effect. For full activity purified Gin protein must be supplemented with crude host factor from E. coli K12. We suggest that, in addition to Gin, a DNA-binding host protein is required for efficient G inversion.

Bacterial Proteins↗
PubMed1984

The genetic organization of integrated hepatitis B virus DNA in the human hepatoma cell line PLC/PRF/5.

Hepatitis B virus (HBV) DNA is often found integrated in the genome of infected human liver cells and is supposed to be related to the development of primary liver carcinoma (PLC). Four clones of HBV DNA-containing sequences derived from DNA of the human PLC-derived cell line PLC/PRF/5 are discussed. The viral sequences show no intricate rearrangements excepting for a duplication and an inversion in one case, and a deletion in another. In all cases integration of the viral DNA was seen to be in a region which is single-stranded in the unintegrated HBV DNA. Sequence homologies between human and viral DNA flanking the integration sites have been detected. That may have a functional role in integration. Nucleotide sequence analyses of regions encompassing the viral-human junctions reveal open reading frames which consist of viral and/or human information. The possible expression of chimeric or cellular proteins may play a role in tumour development, and offers directions for further investigations.

Base Sequence↗
PubMed1984

Gin-mediated site-specific recombination in bacteriophage Mu DNA: overproduction of the protein and inversion in vitro.

Inversion of the G segment in bacteriophage Mu DNA occurs by a site-specific recombination event and determines the host specificity of Mu phage particles produced. Inversion is mediated by a Mu function (Gin). The gin gene has been placed under control of the inducible lambda pL promoter and a synthetic Shine-Dalgarno linker upstream of the initiation codon. The Gin protein content in induced cells is boosted to 10% of total protein. Partially purified extracts from overproducing strains promote efficient inversion of the G DNA segment in vitro which is visualized by agarose gel electrophoresis of the substrate DNA after cutting with appropriate restriction endonucleases. The in vitro reaction requires Mg, a super-coiled DNA substrate and occurs in the absence of exogenous ATP. Inversion from the G(+) to the G(-) orientation is as efficient as the switch from G(-) to G(+).

Journal Article↗
PubMed1983

Integration of hepatitis B virus DNA: evidence for integration in the single-stranded gap.

The DNA of hepatitis B virus (HBV) can integrate into the genomes of infected human liver cells and may be related to the development of primary liver carcinoma (PLC). This report describes the analysis of three integrated HBV DNA sequences cloned from DNA of the human PLC cell line PLC/PRF/5. In all these sequences, integration of the viral DNA is at a site that is single-stranded (gap) in the unintegrated HBV DNA. Contrary to some speculations, there are no large terminal redundancies flanking the inserts as found in retroviral proviruses. The viral sequences show no obvious rearrangements in these clones, but integration can be associated with deletions in the viral DNA and also apparently in the host DNA.

Base Sequence↗
PubMed1982

Nucleotide sequence of the immunity region of bacteriophage Mu.

The leftmost 1590 bp of Mu DNA covering the immunity region have been sequenced. This region encodes the cI repressor, the cII or ner function and the beginning of gene A. An open reading frame extends from position 863 to 342 on the l-strand corresponding to cI protein with a molecular weight of 19212. It is preceded by a sequence resembling a promoter. To the right of the HindIII site an open reading frame extends from position 1099 to 1323 corresponding to cII or ner protein (molecular weight of 8505) followed by the beginning of gene A at position 1328. Between position 863 and 1099 promoters for leftward and rightward transcription and operator-like structures can be recognized in the sequence. The promoter for rightward transcription overlaps with the HindIII site and coincides with a RNA polymerase binding site as demonstrated by electron microscopy.

Bacteriophage mu↗
PubMed1981

The relationship of two invertible segments in bacteriophage Mu and Salmonella typhimurium DNA.

A Mu gin- mutant which lacks the function required for inversion of the G segment can be complemented by hybrid plasmids and phages carrying the invertible segment that controls flagellar phase variation in Salmonella typhimurium. This suggests that the same kind of site-specific recombination mechanism is responsible for these inversions. Based on the different features of the two invertible segments we propose a model for their evolutionary relationship.

Genetic Complementation Test↗
PubMed1977

Mapping of restriction sites in the attachment site region of bacteriophage lambda.

A find structure map of the EcoRI fragment containing the lambda attachment-site region has been constructed. 38 different restriction endonucleases have been employed and 170 sites located in this fragment. In addition, sites in adjacent regions have been determined for several enzymes. Complete cleavage maps of the entire lambda genome have been obtained for endonucleases BglII, BluI, KpnI, SacI, SacII, SalI and XbaI. The strategy employed for mapping included comparison of deletion and substitution mutants, analysis of mixed digests, and detailed analysis of subfragments.

Chromosome Mapping↗
PubMed1976

Transfection of Escherichia coli by Mu DNA.

Infectivity of Mu DNA was demonstrated in Ca+ +-treated Escherichia coli cells that lacked the nucleases Exo V and Endo I. The efficiency of transfection is about 10(-7) per phage equivalent. Infectivity is destroyed by denaturation of Mu DNA, and cannot be restored by renaturation.

Calcium↗