Checkpoint activation regulates mutagenic translesion synthesis.

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Cells possess sophisticated checkpoint mechanisms to manage genomic damage, involving cell cycle arrest, DNA repair, and apoptosis.
• Translesion synthesis (TLS) pathways provide an alternative strategy to tolerate DNA lesions, employing either error-free or error-prone polymerases.
• The interplay between checkpoint control and TLS in response to replication stress remains incompletely understood.

Purpose of the Study:

• To investigate the functional relationship between DNA replication checkpoints and translesion synthesis pathways.
• To determine how checkpoint activation influences the expression and localization of TLS polymerases.
• To elucidate the role of specific checkpoint proteins in regulating TLS activity.

Main Methods:

• Analysis of cellular phenotypes, including mutation rates, following replication perturbation in wild-type and mutant yeast strains.
• Quantitative assessment of DinB (a TLS polymerase) expression and chromatin association.
• Co-immunoprecipitation assays to examine physical interactions between TLS polymerases and checkpoint proteins.

Main Results:

• Replication perturbation induces a mutator phenotype, modulated by mutations in checkpoint genes (Cds1, Rad17) and TLS polymerases (DinB, Polzeta).
• DinB expression is upregulated in a checkpoint-dependent manner upon genomic perturbation.
• Chromatin association of DinB requires functional Rad17 and physical interaction with checkpoint clamp proteins (Hus1, Rad1).

Conclusions:

• Translesion synthesis is not merely a passive tolerance mechanism but an active component of the cellular checkpoint response to replication stress.
• Checkpoint proteins play a critical role in regulating the recruitment and activity of TLS polymerases at sites of DNA damage.
• This integrated response ensures genomic integrity by balancing lesion tolerance and checkpoint control.