Fig. 1.

Comparison of degron approaches. a Proteins with a zinc finger 1 degron (ZF1, red) are stable before expression of the ubiquitin ligase adaptor ZIF-1 (blue) in C. elegans embryos. ZIF-1 starts to be expressed in a stereotyped pattern of somatic cells after the two-cell stage, starting with the anterior cells (red + blue = purple). Proteins with a ZF1 tag are degraded in somatic cells, starting with the anterior cells (purple to blue). Cells that do not express ZIF-1, such as the posterior germ cell, do not degrade proteins with a ZF1 tag (red). b The C-terminal phosphodegrons (CTPD) of OMA-1 are inert until phosphorylated and CTPD-tagged proteins (red) are stable, despite the presence of SCF ubiquitin ligases (blue). Phosphorylation of CTPD occurs during the first mitosis in C. elegans embryos, leading to degradation of CTPD-tagged proteins during the first cell division. c Expression of the TIR1 ligase adaptor (blue) is not sufficient to induce robust degradation of proteins tagged with the auxin-inducible degron (AID, red). Addition of auxin family hormones induces degradation of AID-tagged proteins in cells where TIR1 is expressed (purple to blue)