Molecular Genetics

Facts

• Cells contain a DNA-activated protein kinase. It is activated only by DNA containing free ends, not by intact circular DNA.
• Cells also contain an ADP-ribosylase that is activated by DNA damage. Mitotitc recombination is stimulated by DNA damage (MCB 8:196).
• Saccharomyces cervisiae cells arrest in G2 of the cell cycle if their DNA is damaged by X-Ray radiation or if replication can not be completed due to a failure to ligate DNA fragments (cdc9 mutation).
• Second site mutations in the RAD9 gene alleviate the cell cycle block caused by X-Rays or cdc9.

Interpretations

• Cell division is delayed until DNA damage is repaired.
• The signal for this delay likely is free DNA ends.

Further information

• The precise mechanism of coupling of DNA damage to the cell cycle involves a complex pathway of downstream interactions (ref).

This is page 3135 of Molecular Genetics by Ulrich Melcher, © 1997, 1998, 1999