DNA replication reaches the breaking point

Abstract

DNA strand breaks that result in stalled or damaged replication forks can be detrimental to the DNA replication process. In this issue, Doksani et al. (2009) examine the impact of a single double-stranded DNA break on replication in the budding yeast, Saccharomyces cerevisiae.

Figure 1. Sister Forks and DNA Double-Strand Breaks

The behavior of sister forks emanating from the replication origin ARS305 (yellow circle) in budding yeast has been analyzed (Doksani et al., 2009). The sister forks, 305R (which encounters the DNA double-strand break) and 305L, do not appear to be coupled, because when the 305R fork replisome disengages from the DNA break site there is no effect on the progress of the 305L fork. Induction of a specific DNA double-strand break by the HO endonuclease of budding yeast locally enhances firing of the origin of replication (pale green arrow). Formation of a DNA cruciform structure at the break site is suppressed by the Mre11 complex, and by the proteins Tel1 and Sae2. (306L is the left sister fork of the ARS306 origin, which is to the right of the break site induced by the HO endonuclease.)