Related Experiment Video
Updated: Aug 8, 2026

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
The budding yeast Rad9 checkpoint protein is subjected to Mec1/Tel1-dependent hyperphosphorylation and interacts with
J E Vialard1, C S Gilbert, C M Green
1Imperial Cancer Research Fund, Clare Hall Laboratories, CDC Laboratory, South Mimms, Hertfordshire EN6 3LD, UK.
Abstract:
The Saccharomyces cerevisiae RAD9 checkpoint gene is required for transient cell-cycle arrests and transcriptional induction of DNA repair genes in response to DNA damage. Polyclonal antibodies raised against the Rad9 protein recognized several polypeptides in asynchronous cultures, and in cells arrested in S or G2/M phases while a single form was observed in G1-arrested cells. Treatment with various DNA damaging agents, i.e. UV, ionizing radiation or methyl methane sulfonate, resulted in the appearance of hypermodified forms of the protein. All modifications detected during a normal cell cycle and after DNA damage were sensitive to phosphatase treatment, indicating that they resulted from phosphorylation. Damage-induced hyperphosphorylation of Rad9 correlated with checkpoint functions (cell-cycle arrest and transcriptional induction) and was cell-cycle stage- and progression-independent. In asynchronous cultures, Rad9 hyperphosphorylation was dependent on MEC1 and TEL1, homologues of the ATR and ATM genes. In G1-arrested cells, damage-dependent hyperphosphorylation required functional MEC1 in addition to RAD17, RAD24, MEC3 and DDC1, demonstrating cell-cycle stage specificity of the checkpoint genes in this response to DNA damage. Analysis of checkpoint protein interactions after DNA damage revealed that Rad9 physically associates with Rad53.
Related Concept Videos
Negative Regulator Molecules
DNA Damage can Stall the Cell Cycle
Homologous Recombination
Restarting Stalled Replication Forks
The Spindle Assembly Checkpoint
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
DNA Damage Can Stall the Cell Cycle

