DNA polymerase I and a protein complex bind specifically to E. coli palindromic unit highly repetitive DNA: implications for bacterial chromosome organization

Nucleic Acids Res. 1990 Jul 11;18(13):3941-52. doi: 10.1093/nar/18.13.3941.


Starting from a crude E. coli extract, two activities which specifically protect highly repetitive bacterial DNA sequences (called PU for Palindromic Unit or REP for Repetitive Extragenic Palindromic sequence) against a digestion with Exonuclease III have been purified. We show that one of these activities is due to the DNA polymerase I (Pol I). This constitutes the first indication for a specific interaction between Pol I and a duplex DNA. This interaction requires the presence of PU. It was confirmed and analyzed by native gel electrophoresis and DNase I footprinting experiments. The other activity contained at least five polypeptides. Its binding to PU DNA sequences was confirmed by native gel electrophoresis. Implications for the possible origin and functions of PU are discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Chromosome Mapping
  • Chromosomes, Bacterial*
  • DNA Polymerase I / metabolism*
  • DNA, Bacterial / metabolism*
  • DNA, Circular / metabolism
  • DNA-Binding Proteins / metabolism
  • Deoxyribonuclease I / metabolism
  • Electrophoresis
  • Escherichia coli / enzymology
  • Escherichia coli / genetics*
  • Exodeoxyribonucleases / metabolism
  • Molecular Sequence Data
  • Repetitive Sequences, Nucleic Acid*
  • Restriction Mapping


  • Bacterial Proteins
  • DNA, Bacterial
  • DNA, Circular
  • DNA-Binding Proteins
  • DNA Polymerase I
  • Exodeoxyribonucleases
  • exodeoxyribonuclease III
  • Deoxyribonuclease I