The Notch intracellular domain is ubiquitinated and negatively regulated by the mammalian Sel-10 homolog.
The Caenorhabditis elegans sel-10 protein is structurally similar to E3 ubiquitin ligases and is a negative regulator of Notch (lin-12) and presenilin signaling. In this report, we characterize the mammalian Sel-10 homolog (mSel-10) and analyze its effects on Notch signaling. We find that mSel-10 localizes to the cell nucleus, and that it physically interacts with the Notch 1 intracellular domain (IC) and reduces Notch 1 IC-mediated activation of the HES 1 promoter. Notch 1 IC is ubiquitinated by mSel-10, and ubiquitination requires the presence of the most carboxyl-terminal region of the Notch IC, including the PEST domain. In the presence of the proteasome inhibitor MG132, the amount of Notch 1 IC and its level of ubiquitination are increased. Interestingly, this accumulation of Notch 1 IC in the presence of MG132 is accompanied by decreased activation of the HES 1 promoter, suggesting that ubiquitinated Notch 1 IC is a less potent transactivator. Finally, we show that mSel-10 itself is ubiquitinated and degraded by the proteasome. In conclusion, these data reveal the importance of ubiquitination and proteasome-mediated degradation for the activity and turnover of Notch ICs, and demonstrate that mSel-10 plays a key role in this process.
Oberg
C
C
Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institute, SE-171 77 Stockholm, Sweden.
Li
J
J
Pauley
A
A
Wolf
E
E
Gurney
M
M
Lendahl
U
U
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D017173:Caenorhabditis elegans / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000378:metabolism; D015801:Helminth Proteins / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D051880:Receptors, Notch; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism; D014452:Ubiquitins / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D015801:Helminth Proteins; D008565:Membrane Proteins; D051880:Receptors, Notch; C109554:SEL-10 protein, C elegans; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D014452:Ubiquitins