Fig 2. Rif1 acts together with Sir2 to inhibit rDNA origin firing, but independently to block late origin firing.

(A-B) Relative BrdU incorporation at the indicated loci (A) and 2D agarose gel electrophoresis (B) in WT, rif1Δ, sir2Δ, and rif1Δ sir2Δ mutant cultures released from nocodazole (G2/M) arrest into 0.2 M HU for 2 hrs. Data are presented as mean +/- SEM of three independent experiments and a t-test was used to compare the means of WT and mutant cultures. (*) P < 0.05.