Distinct mechanisms of replication stress induced by oncogenic RAS and cyclin E1 converge on R-loop-dependent fork...

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Activated oncogenes induce genomic instability by creating DNA replication stress.
• Co-transcriptional RNA:DNA hybrids (R-loops) are implicated in replication stress and chromosome mis-segregation.

Purpose of the Study:

• To investigate the role of R-loops in replication stress and chromosome mis-segregation induced by oncogenic RAS or cyclin E1.
• To elucidate the mechanisms underlying replication stress, including the involvement of reactive oxygen species (ROS) and specific proteins.

Main Methods:

• Overexpression of oncogenes (HRASV12, cyclin E1) in cell models.
• Analysis of replication fork dynamics, R-loop formation, and chromosome segregation.
• Investigating the roles of ROS, peroxiredoxin 2 (PRDX2), TIMELESS, MUS81, and PRIMPOL.

Main Results:

• Oncogene-induced replication stress and chromosome mis-segregation are largely driven by R-loops.
• HRASV12-induced stress involves ROS, PRDX2, and TIMELESS release, while cyclin E1's effect is independent of ROS.
• Inhibiting fork reversal promotes DNA synthesis via MUS81 and PRIMPOL, ensuring proper mitosis.

Conclusions:

• PRIMPOL repriming is crucial for MUS81-dependent replication restart at R-loop sites, maintaining genomic stability.
• Persistent reversed forks, while protective in S-phase, can lead to mitotic errors and DNA damage.