Fig. 3.

Autoradiogram of 2D gels of replication intermediates generated in the presence of HU. HU-induced replication stress eliminates fork arrest at the natural fork barriers Ter1–Ter3 but introduces numerous new pause sites. Shown is 2D gel analysis of the BamHI fragment of WT (SP976) cells, grown in the absence (–HU) and presence (+HU) of 12 mM HU for 3.5 h. Although the region is actively replicated, the Swi1p- and Swi3p-dependent Ter1–Ter3 are abolished in the presence of HU, whereas the Swi1p- and Swi3p-independent RFP4 is unaffected, accumulating an excess of forks. Note also the appearance of numerous pause sites on the descending arc (arrowheads).