Mammalian DET1 regulates Cul4A activity and forms stable complexes with E2 ubiquitin-conjugating enzymes.
DET1 (de-etiolated 1) is an essential negative regulator of plant light responses, and it is a component of the Arabidopsis thaliana CDD complex containing DDB1 and COP10 ubiquitin E2 variant. Human DET1 has recently been isolated as one of the DDB1- and Cul4A-associated factors, along with an array of WD40-containing substrate receptors of the Cul4A-DDB1 ubiquitin ligase. However, DET1 differs from conventional substrate receptors of cullin E3 ligases in both biochemical behavior and activity. Here we report that mammalian DET1 forms stable DDD-E2 complexes, consisting of DDB1, DDA1 (DET1, DDB1 associated 1), and a member of the UBE2E group of canonical ubiquitin-conjugating enzymes. DDD-E2 complexes interact with multiple ubiquitin E3 ligases. We show that the E2 component cannot maintain the ubiquitin thioester linkage once bound to the DDD core, rendering mammalian DDD-E2 equivalent to the Arabidopsis CDD complex. While free UBE2E-3 is active and able to enhance UbcH5/Cul4A activity, the DDD core specifically inhibits Cul4A-dependent polyubiquitin chain assembly in vitro. Overexpression of DET1 inhibits UV-induced CDT1 degradation in cultured cells. These findings demonstrate that the conserved DET1 complex modulates Cul4A functions by a novel mechanism.
Pick
Elah
E
Department of Molecualr, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA.
Lau
On-Sun
OS
Tsuge
Tomohiko
T
Menon
Suchithra
S
Tong
Yingchun
Y
Dohmae
Naoshi
N
Plafker
Scott M
SM
Deng
Xing Wang
XW
Wei
Ning
N
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D044842:Cullin Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000528:radiation effects; D011499:Protein Processing, Post-Translational / Q000528:radiation effects; D021122:Protein Subunits / Q000378:metabolism; D013379:Substrate Specificity / Q000528:radiation effects; D013816:Thermodynamics; D025801:Ubiquitin / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry / Q000378:metabolism*; D014466:Ultraviolet Rays
C467199:CDT1 protein, human; C114234:CUL4A protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; C091435:DDB1 protein, human; C482641:DET1 protein, human; D004268:DNA-Binding Proteins; D021122:Protein Subunits; D025801:Ubiquitin; D044763:Ubiquitin-Conjugating Enzymes