Figure 6.

A Model for Loss of Repressive Histone Marks at Sites with G4-Forming Potential in rev1 Cells

Replication is depicted arresting at a G4 DNA on the leading-strand template. Parental histones are shown as light-gray circles, with repressive epigenetic marks represented as gray bars. New histones are shown in black. If REV1 is present, the fork can replicate through the G4 DNA, maintaining processive DNA synthesis and histone deposition. It is not clear whether the presence of REV1 prevents the formation of the structure or assists in its unwinding (see also Figure S2). In the absence of REV1 the fork remains arrested at the G4 DNA, resulting in a postreplicative gap. The DNA synthesis associated with the resolution of this gap and of the G4 DNA is accompanied by new histone incorporation resulting in a tract of chromatin lacking the parental epigenetic marks.