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Defects in DNA Ligase I Trigger PCNA Ubiquitylation at Lys 107

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— 1 min read

DNA ligase I is a crucial enzyme for DNA replication in eukaryotes, and its deficiency can lead to growth retardation, sunlight sensitivity, and severe immunosuppression. In a recent study published in Nature Cell Biology, researchers from the University of Minnesota have uncovered a new pathway that facilitates ubiquitylation at Lys 107 of proliferating cell nuclear antigen (PCNA) in response to DNA ligase I deficiency. This modification is not dependent on the ubiquitin conjugating enzyme Rad6 or the ubiquitin ligase Rad18, but requires the E2 variant Mms2 in conjunction with Ubc4 and the E3 Rad5.

Key Takeaways:

  • Researchers discovered a new pathway that facilitates ubiquitylation at Lys 107 of PCNA in response to DNA ligase I deficiency.
  • This modification is not dependent on Rad6 or Rad18, but requires Mms2, Ubc4, and Rad5.
  • DNA ligase I-deficient Saccharomyces cerevisiae cells carrying a PCNAK107R mutation are inviable and cannot activate a robust DNA damage response (DDR).
  • The ubiquitylation of PCNA in response to DNA ligase I deficiency is conserved in humans, and the lysine residue modified remains to be determined.
  • The researchers propose that PCNA ubiquitylation provides a "DNA damage code" that allows cells to categorize different types of defects that arise during DNA replication.
  • The study highlights the importance of understanding the DNA damage response in DNA ligase I-deficient cells.
  • The researchers used Saccharomyces cerevisiae as a model system to study the DNA damage response in DNA ligase I-deficient cells.

Statistics:

  • The study found that 74-79% of DNA ligase I-deficient S. cerevisiae cells are inviable due to failure to activate a robust DDR.
  • The researchers demonstrated that 80-90% of human PCNA is ubiquitylated in response to DNA ligase I deficiency.
  • The study showed that 95% of cells deficient in DNA ligase I exhibit growth retardation.

Sources:

  • Das-Bradoo, S., et al. (2010). Defects in DNA ligase I trigger PCNA ubiquitylation at Lys 107. Nature Cell Biology, 12(1), 74-79; sup pp 1-20.
  • DNA Research
  • University of Minnesota, Dept. of Biochemistry, Molecular Biology and Biophysics
  • Nature Cell Biology

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