Open AccessMutations in the E. coli Rep helicase increase the amount of DNA per cell
Author(s) -
Trun Nancy
Publication year - 2003
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1016/s0378-1097(03)00595-0
Subject(s) - biology , genetics , helicase , dna , microbiology and biotechnology , mutation , gene , circular bacterial chromosome , allele , dna replication , rna
The mbrA4 mutation confers camphor resistance, severe growth defects and up to a two‐fold increase in the amount of chromosomal DNA per cell. The extra DNA is replicated from oriC in a synchronous fashion. Cells containing mbrA4 are more resistant to X‐rays, indicating that the extra DNA represents complete or nearly complete chromosomes. I report here that mbrA4 is an unusual allele of the leading strand DNA helicase, Rep. Eight independently isolated alleles of rep(mbrA) contain the same three changes in the rep gene: a G to A at position −44 from the start of the mRNA (+1); an opal stop at codon 142; and a glycine to serine at codon 414 (G414S). My data indicate that rep(mbrA4) is not a null mutation and that the third mutation, G414S, is necessary for camphor resistance, the phenotype associated with increased DNA content per cell. I also show that increase in DNA content does not lead to independently segregating chromosomes.