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. 2021 Aug 4;10:e65467. doi: 10.7554/eLife.65467

Figure 3. Overlapping chromosome arm alignment patterns for wild-type Smc.

(A) Normalized 3C-seq contact maps for strains with a single parSopt site at −9 kb, −304 kb, or +328 kb. Dark gray triangles above the contact maps indicate the presence of active parS sites. Light gray triangles for reference are parS sites absent in the given experiment. Schemes depict a ‘loop contact’ that emerges by bidirectional translocation of a Smc unit from a single loading site (yellow), here +328kbparSopt. (B) Normalized 3C-seq contact maps for strains with two parSopt sites spaced by ~300 kb (left and middle) or ~600 kb (right). Schemes interpreting interactions in the contact maps: loop contacts (in yellow colors) and ‘paired-loop contacts’ that we presume to emerge by collision of two convergently translocating Smc units loaded at opposite parS sites (in orange colors). (C) Ratio plots for ChIP-seq read counts for a strain with two parS sites (left panel: –304kbparSopt and –9kbparSopt; right panel: –9kbparSopt and +328kbparSopt) and a control strain with a single parS site (–9kbparSopt). Representation as in Figure 2B. (D) Schemes depicting possible scenarios for long-distance contacts emerging by bidirectional Smc translocation with collision avoidance and collision resolution: Smc traversal (1), reversal (2), unloading upon collision (3), or low Smc flux (4).

Figure 3.

Figure 3—figure supplement 1. Wild-type Smc protein generates overlapping chromosome folding patterns.

Figure 3—figure supplement 1.

(A) RNAP inhibition experiment using rifampicin. Normalized 3C-seq contact maps for strains with two parSopt sites spaced by ~300 kb (mock treatment control ‘rif-’, top panel) (rif treatment ‘rif+’, bottom panel). (B) Schemes depicting possible scenario for collision avoidance and collision resolution: exclusive usage of a single parS site by SMC complexes as a consequence of temporary inactivation of remaining parS sites. (C) Read count distribution for chromatin immunoprecipitation coupled to deep sequencing (ChIP-seq) using α-ScpB serum for a strain with eight parS sites deleted, single parSopt at −9 kb, two parS sites at −304 kb and −9 kb, −9 kb and +328 kb or −304 kb and +328 kb. Represented as in Figure 2—figure supplement 1B. (D) Read count distribution for chromatin immunoprecipitation coupled to deep sequencing (ChIP-seq) using α-ParB serum as in (C).