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. 2015 Jun 25;34(16):2182–2197. doi: 10.15252/embj.201591190

Figure 7.

Figure 7

Model of Mec1 activation promoted by Slx4 complex assembly

  1. Mec1 phosphorylation of H2A serine 129 nucleates assembly of Slx4 complexes by providing a binding site for the C-terminal BRCT pair of Rtt107. Slx4 binds Rtt107 constitutively via its C-terminal Rtt107 binding domain. Phosphorylation of Slx4, by Cdk and Mec1, creates binding sites for the N-terminal BRCT pair of Dpb11, whereas the C-terminal BRCT pair binds Ddc1 phosphorylated on threonine 602 by Mec1. Engagement of both Dpb11 BRCT pairs results in stable complex formation distal to the MMS-stressed replication fork, and promotes Mec1 kinase activity, resulting in a positive feedback loop that amplifies Mec1 signaling. Phosphorylations are indicated by gray lines, and protein–protein interactions are indicated by black lines.
  2. A model of Slx4 complex assembly, with three possible modes of Mec1 activation indicated.