Checkpoint effects and telomere amplification during DNA re-replication in fission yeast

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Mechanisms preventing DNA replication re-initiation are known, but susceptible regions and checkpoint pathway roles during bypass are unclear.
• Investigating DNA re-replication in fission yeast (Schizosaccharomyces pombe) provides insights into these less-understood processes.

Purpose of the Study:

• To identify genomic regions susceptible to DNA re-replication when normal controls are bypassed.
• To determine the extent to which checkpoint pathways modulate DNA re-replication.

Main Methods:

• Utilized microarray analysis in wild-type and checkpoint-mutant fission yeast strains.
• Over-expressed a non-phosphorylatable form of the replication-initiation protein Cdc18.

Main Results:

• Forced re-replication occurred genome-wide, not limited to specific sequences.
• Replication amplification varied, with regions spanning hundreds of kilobases showing moderate changes.
• Telomere-proximal regions were particularly susceptible to re-replication, independent of replication origins.
• Checkpoint mutants (rad3 and cds1) showed similar re-replication patterns to wild-type, with minor effects in rad3 mutants.

Conclusions:

• Replication origins and fork progression during re-replication are largely independent of Cds1 and Rad3 checkpoint pathways.
• The observed pattern of telomere-proximal amplification and adjacent under-replication in fission yeast is conserved in budding yeast.
• Subtelomeric sequences are potential targets for studying DNA re-replication in other organisms.