The oxidative stress responsive transcription factor Pap1 confers DNA damage resistance on checkpoint-deficient...

Area of Science:

• Cellular biology
• Molecular genetics
• DNA repair mechanisms

Background:

• Eukaryotic cells possess mechanisms to survive genomic stress and damage.
• The protein kinase Chk1 is crucial for the DNA damage response, with its mutation leading to cell death upon DNA damage.
• Oxidative stress triggers the nuclear accumulation of the bZIP transcription factor Pap1.

Purpose of the Study:

• To investigate the role of fission yeast Pap1 in conferring resistance to DNA damage.
• To determine if Pap1 provides protection when the DNA damage checkpoint is compromised.
• To explore the impact of Pap1 expression on cells with defects in DNA repair pathways.

Main Methods:

• Assessing cell survival in response to DNA damaging agents (camptothecin, hydroxyurea) under various genetic conditions.
• Evaluating the effect of multi-copy Pap1 expression in chk1-deficient cells.
• Investigating Pap1's role in cells with mutations in DNA ligase (cdc17), DNA polymerase δ (cdc6), and DNA replication initiation genes.
• Testing Pap1's efficacy in rad1- and rad9-deficient cells.
• Analyzing the requirement for Pap1 nuclear localization and transcriptional activity for DNA damage resistance.

Main Results:

• Fission yeast Pap1 confers resistance to drug- and non-drug-induced DNA damage, even in the absence of a functional DNA damage checkpoint (chk1-deficient cells).
• Multi-copy Pap1 expression rescues the growth of chk1-deficient cells treated with camptothecin or hydroxyurea.
• Increased Pap1 expression promotes survival in chk1-deficient cells with mutations in DNA ligase (cdc17) or DNA polymerase δ (cdc6), but not in replication initiation mutants.
• Pap1-mediated resistance is not exclusive to chk1 mutants, as it also improves survival in rad1- and rad9-deficient cells.
• Pap1 must be transcriptionally active and localized to the nucleus to confer DNA damage resistance.

Conclusions:

• Fission yeast Pap1 plays a significant role in DNA damage resistance, independent of the Chk1-mediated DNA damage checkpoint.
• Pap1's protective function extends to various DNA repair deficiencies, highlighting its broad importance in maintaining genomic integrity.
• Nuclear localization and transcriptional activity are essential for Pap1's DNA damage resistance function.