Release of CHK-2 from PPM-1.D anchorage schedules meiotic entry

Transition from the stem/progenitor cell fate to meiosis is mediated by several redundant posttranscriptional regulatory pathways i

The Study of the SCF E3 Ubiquitin Ligase in the Ceanorhabditis elegans Germline

Faithful chromosome segregation during meiosis requires chromosomes to pair and recombine with their homologous partners during meiotic prophase I. In most eukaryotes, homologous chromosome alignment is reinforced by synapsis, a process defined by the assembly of the synaptonemal complex (SC), a tripartite protein structure that assembles between homologous chromosomes. These processes of pairing, synapsis, and meiotic recombination are tightly regulated and aligned with different phases of the cell cycle. One defining aspect of the cell cycle is its irreversible nature, which is made possible only by the protein degradation that occurs as the cell progresses from one phase to the next. Understanding how protein degradation controls pairing, synapsis, and meiotic recombination allows us to understand how protein degradation regulates the meiotic cell cycle. To investigate the ways in which protein degradation controls meiotic processes, I studied the nematode Caenorhabditis elegans and the E3 ubiquitin ligase, the SCF (SKP1-Cullin-F-box) complex. I used a mix of genetics, cellular biology, and biochemistry to identify new interacting proteins, possible targets, and potential regulatory subunits of the SCF within C. elegans. I found that SCFPROM-1 targets the protein phosphatase PPM-1.D at the onset of meiotic entry, which in turn releases the kinase CHK-2, the master regulator of early meiotic processes. I also found that two paralogous SKP1 proteins moonlight as necessary structural components of the synaptonemal complex. These proteins have evolved to utilize the binding interfaces between SKP1-Cullins and SKP1-F-box proteins to interact with themselves to form a dimer or to interact with the surrounding SC proteins. In addition to identifying these proteins as SC components, we have shown that they are the last two necessary SC components, completing the essential set and allowing for in vitro reconstitution of the SC. Overall, this work provides a better understanding of how protein degradation and its machinery regulate the meiotic cell cycle and its various processes