Fig. 4.

Condensation of Mlh1 and Mlh3 through NTD and CTD interactions. (A) Schematic representation of the four conformational states proposed for MutL homologs from AFM studies. (B and C) Surface representation of the NTD and CTD of Mlh1 and Mlh3 colored according to conservation rate of the amino acids (B) and to electrostatic potential (C). Two conserved basic residues in Mlh3-NTD (K316 and K320) and three conserved acid residues in Mlh3-CTD (E565, D611 and D625) are proposed to contribute to the condensation of the full-length heterodimer through their interaction in the condensed state. The five corresponding mutations in Mlh3(NTD) (MN1 and MN2) and in Mlh3(CTD) (MC1, MC2, and MC3) performed in this study are indicated. The structure of Mlh1 and Mlh3 NTDs were modeled from the crystal structures of MutL NTDs. (D) Spore viability of diploid strains bearing the indicated mlh3 genotype at its endogenous locus. The dotted lines indicate MLH3 (WT) and mlh3∆ spore viability levels for comparison. ***P < 0.001, **P < 0.01, Fisher’s exact test. Refer also to SI Appendix, Table S2. (E) Crossing over frequency at the HIS4LEU2 hotspot monitored by Southern blot. Graph shows quantification from three independent biological replicates ± SD, except for mlh3MC1MC2 (two replicates, mean values ± range), and are expressed relative to levels in MLH3 (same strains as in D).