Working model for MPS1 replication pausing and mat1 imprinting.

The mat1 locus and the events that occur during replication of it are depicted with line drawings. Left, molecular events that take place in the wild-type strain. Right, events occurring when cis-acting mutations are introduced. Positions of the spacer and abc regions and the H1 domain (grey boxes) are shown. The orientations of the DNA strands are indicated. The putative proteins mediating MPS1 activity and maintenance of the imprint are displayed as a circle and a pentagon, respectively. The imprint is marked with a black spot. Leading- and lagging-strand replication is represented with black half arrowheads. Specific priming is depicted as wavy lines, while loss of it is indicated with grey half arrowheads. Left, positions of the cis-acting deletions are given. See main text for description of each step.