Stochastic assembly of sister replisome pairs recapitulates their observed distribution at individual replication factories. (A) Distribution of the number of sister replisome pairs per replication factory (Fig. 3 E) approximately fits a Poisson distribution (λ = 1.60, R2 = 0.98). (B) Schematic diagram of “Particles on a string” model. See detail in Materials and methods, Mathematical modeling i. (C) We fitted the parameter A in P(d) = 1/(Ad3 + 1), using the replicon assembly frequency result, obtained in strain #1 and #2 (Fig. 2 A; 23 and 19 cells were analyzed, respectively). Fig. S3 B explains how the chromosomal distance between sister replisome pairs was obtained in strain #1, #2, and #3. (D) Schematic diagram showing the example of positions of sister replisome pairs along a chromosome (top), and their stochastic assembly (bottom) based on the grouping probability shown in C. (E) Distribution of the distance (replicated DNA is not counted, as it is looped out; see C) between neighboring sister replisome pairs along a chromosome, obtained from the simulation. Relative fractions of the pairs at the indicated distance (each 5-kb window) were obtained from one million simulations, at the peak of DNA replication (at 30 min in Fig. 3 C). Fractions for >250 kb are shown together at 250 kb. (F) Distributions of the number of sister replisome pairs per replication factory: comparison between in vivo data (obtained in Fig. 3 E) and in silico data (as shown in B–E). Pearson correlation coefficient r = 0.9953. P < 0.0001.
