| Comments |
P.2 right column 2nd paragraph: "The molecular function of DET1 is less well understood, in part because the CDD-CUL4 complex lacks a DWD protein with a WDXR motif, which is the typical substrate recognition motif for CUL4–DDB1 ligases. This makes it more challenging to understand the mechanism of this E3 ligase complex. In addition to its role in the CDD complex, DET1 has been implicated in chromatin regulation and shown to act as a transcriptional co-repressor (Benvenuto et al. 2002, Dong et al. 2014). It has repression activity in vivo and can interact with the core clock genes circadian clock associated 1 (CCA1) and late elongated hypocotyl 1 (LHY) to mediate the repression of timing of cab expression 1 (TOC1) (Fig. 1) (Dong et al. 2014, Lau et al. 2011). In fact, det1 mutants have an extraordinarily short circadian period, running at ~18.5 h in constant darkness, and ~20 h in constant light (primary source). Recent work has shown that, in the dark, PIF1 interacts with COP1 and enhances E3 ligase activity for elongated hypocotyl 5 (HY5) degradation while, in the light, the phosphorylated form of PIF1 is recruited to the COP1 complex for rapid ubiquitylation and subsequent degradation (Zhu et al. 2015). Dong et al. (2014) showed that DET1 stabilizes PIF proteins and that 56% of genes that are regulated by light and DET1 are also regulated by PIFs. All together, it seems that COP/DET/FUS and the PIFs work in concert to repress photomorphogenesis." CDD=COP10–DET1–DDB1 CUL4=CULLIN4 |