CHK1 phosphorylates PRIMPOL to promote replication stress tolerance

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• DNA replication requires intricate repair and damage tolerance mechanisms to overcome replication stress.
• Key pathways include fork reversal, translesion synthesis, and repriming by specialized polymerases like PRIMPOL.

Purpose of the Study:

• To investigate the utilization and regulation of DNA repair pathways under varying replication stresses.
• To elucidate the role of CHK1 signaling and PRIMPOL in response to lagging-strand priming inhibition.

Main Methods:

• Inhibition of DNA polymerase alpha (POLα) to block lagging-strand priming.
• Overexpression of CLASPIN to modulate CHK1 activation.
• Analysis of replication fork dynamics, DNA repair pathway activation (ATR, CHK1), and cellular fitness.

Main Results:

• POLα inhibition induced RAD51-, HLTF-, and ZRANB3-mediated fork reversal, independent of SMARCAL1.
• ATR was activated, but CHK1 signaling was dampened compared to hydroxyurea treatment.
• CLASPIN overexpression promoted PRIMPOL-dependent repriming, enhancing replication elongation.
• CHK1-mediated phosphorylation of PRIMPOL is critical for DNA damage resistance but can lead to reduced cell fitness due to single-strand gap formation.

Conclusions:

• CHK1-dependent PRIMPOL activation is a key response to replication stress, facilitating DNA synthesis.
• While essential for damage resistance, excessive PRIMPOL activity impacts cell fitness.
• The study reveals a complex interplay between DNA polymerases, repair factors, and signaling pathways in maintaining genome stability.