Simultaneous gain and loss of functions caused by a single amino acid substitution in the beta subunit of Escherichia coli RNA polymerase: suppression of nusA and rho mutations and conditional lethality

Article Abstract:

An investigation was conducted to isolate suppressor mutations in rpoB, the gene coding for the beta subunit of RNA polymerase, which are able to compensate for mutations in nusA, which codes for a transcription termination factor. A suppressor allele, rpoBts8, was identified. Sequence analysis showed that the mutation is due to a phenylalanine substitution in the 522 serine residue. The mutation is pleiotropic and also results in conditional lethality. It is proposed that the mutation identifies a specialized interaction with a transcription factor, the failure of which results in an inability to express some essential genes.

Analysis, Genetic transcription, Transcription (Genetics), RNA polymerases

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DNA inversions between short inverted repeats in Escherichia coli

Article Abstract:

Escherichia coli strains that enable researchers to disclose DNA inversion in the lac region were constructed by site-specific mutation determine the role of recombination in genetic rearrangement in the bacteria. It was shown that the region that can be inverted is flanked by inverted repeats 12- to 23-base pair long. Inversion is very much reduced in strains lacking RecA, RecB or RecC. This implies that these three Rec systems including RecD can mediate short repeat rearrangement and perhaps even genomic rearrangement.

Inversion (Genetics)

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The influence of primary and secondary DNA structure in deletion and duplication between direct repeats in Escherichia coli

Article Abstract:

A system to measure the frequency of deletions and duplications between direct repeats was described. The dideoxy nucleotide chain termination method was used to determine DNA sequencing and the reaction was carried out at 45 degrees Celsius. Products were resolved using a denaturing polyacrylamide gel in TBE buffer. Results showed that specific mutagenic events are directed by palindromic sequences between repeats. Multiple internal repeats correlated with increased frequency of deletions between direct repeats.

Chromosome abnormalities, Chromosome deletion, Insertion elements, DNA, DNA insertion elements

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