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Xeroderma pigmentosum complementation group A protein acts as a processivity factor

M W Lambert1, L Yang

  • 1Department of Pathology, Laboratory Medicine, UMDNJ-New Jersey Medical School, 185 South Orange Avenue, Newark, New Jersey 07103, USA. mlambert@umdnj.edu

Biochemical and Biophysical Research Communications
|May 18, 2000
PubMed

Insights

The xeroderma pigmentosum complementation group A (XPA) protein corrects DNA repair defects by enabling endonucleases to locate DNA damage more effectively. This suggests XPA protein acts as a processivity factor in DNA repair.

Area of Science:

  • Molecular Biology
  • DNA Repair Mechanisms
  • Biochemistry

Background:

  • Endonucleases in normal cells locate DNA damage via a processive mechanism.
  • In xeroderma pigmentosum complementation group A (XPA) cells, this process is distributive or less processive.
  • The XPA protein is known to cause the DNA repair defect in XPA cells.

Purpose of the Study:

  • To investigate the role of the XPA protein in the target site location mechanism of endonucleases.
  • To determine if XPA protein influences the processivity of endonuclease action on damaged DNA.

Main Methods:

  • Produced and purified recombinant XPA protein from E. coli.
  • Assayed the mechanism of action of XPA endonucleases on UVC-irradiated DNA.
  • Compared endonuclease activity in the presence and absence of recombinant XPA protein.

Main Results:

  • Recombinant XPA protein restored the processive mechanism of action for XPA endonucleases on damaged DNA.
  • The defect in processive DNA damage site location in XPA cells was corrected by the recombinant XPA protein.

Conclusions:

  • The XPA protein functions as a processivity factor for endonucleases involved in DNA repair.
  • Beyond damage recognition/verification, XPA protein plays a role in ensuring efficient DNA repair site location.

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