Extended Data Fig. 9: Overexpression of SMC complexes speeds up the change of Hi-C patterns with time.
From: DNA-loop-extruding SMC complexes can traverse one another in vivo
a, Replication inhibition Hi-C time course following induction of SirA for a strain with parS sites at −27o and −59o. b, The SMC complex (SMC, ScpA and ScpB) was overexpressed in the same background as the strain in panel A. We found that prolonged over-expression of SMC complexes at 90 min and 120 min did not recapitulate the experiments seen in G1 arrested cells in (a) but caused the interaction lines to become shorter. These patterns are likely due to non-specific loading of SMC complexes outside of parS, creating traffic jams along the DNA. In simulations, when we increase the numbers of off-parS loaded extruders, while keeping the numbers of on-parS loaded extruders consistent, we can observe similar changes in the Hi-C maps. Numbers of on-parS versus off-parS loading are average values for the simulation. c, With SMC overexpression, the 60 min time point (following SirA induction) more closely resembles the 90 min point than the 60 m time point with no SMC overexpression. This indicates that increasing the numbers of SMC complexes on the chromosome leads to an increase in the tilts of the hairpin diagonals away from each other.
