Figure 6.

The MER1 regulatory network and the meiotic gene expression program. The UME6 expression wave is divided into two temporal components: an early component including non-Mer1p-regulated mRNAs (including Mer1p mRNA itself), and a later component including the mRNAs whose splicing is dependent on Mer1p. Loss of expression of either of two Mer1p-responsive genes (MER3 and SPO22) arrests the cells at the pachytene checkpoint, which must be passed in order for induction of the subsequent NDT80 expression wave to proceed. However, loss of Mer1p-responsive gene MER2 bypasses recombination and the pachytene checkpoint due to the absence of DSBs. This allows completion of meiosis, even in the absence of MER3 or SPO22. Loss of Mer1p-responsive gene SPO70 arrests the cells after chromosome segregation but before spore formation, later in the meiotic gene expression program. Note that the timing of peak RNA expression precedes the execution points for several of the proteins, presumably due to regulatory events at other levels.