Muf1, a novel Elongin BC-interacting leucine-rich repeat protein that can assemble with Cul5 and Rbx1 to reconstitute a ubiquitin ligase.
The heterodimeric Elongin BC complex has been shown to interact in vitro and in mammalian cells with a conserved BC-box motif found in a growing number of proteins including RNA polymerase II elongation factor Elongin A, SOCS-box proteins, and the von Hippel-Lindau (VHL) tumor suppressor protein. Recently, the VHL-Elongin BC complex was found to interact with a module composed of Cullin family member Cul2 and RING-H2 finger protein Rbx1 to reconstitute a novel E3 ubiquitin ligase that activates ubiquitylation by the E2 ubiquitin-conjugating enzymes Ubc5 and Cdc34. In the context of the VHL ubiquitin ligase, Elongin BC functions as an adaptor that links the VHL protein to the Cul2/Rbx1 module, raising the possibility that the Elongin BC complex could function as an integral component of a larger family of E3 ubiquitin ligases by linking alternative BC-box proteins to Cullin/Rbx1 modules. In this report, we describe identification and purification from rat liver of a novel leucine-rich repeat-containing BC-box protein, MUF1, which we demonstrate is capable of assembling with a Cullin/Rbx1 module containing the Cullin family member Cul5 to reconstitute ubiquitin ligase activity. In addition, we show that the additional BC-box proteins Elongin A, SOCS1, and WSB1 are also capable of assembling with the Cul5/Rbx1 module to reconstitute potential ubiquitin ligases. Taken together, our findings identify MUF1 as a new member of the BC-box family of proteins, and they predict the existence of a larger family of Elongin BC-based E3 ubiquitin ligases.
Kamura
T
T
Howard Hughes Medical Institute and Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA.
Burian
D
D
Yan
Q
Q
Schmidt
S L
SL
Lane
W S
WS
Querido
E
E
Branton
P E
PE
Shilatifard
A
A
Conaway
R C
RC
Conaway
J W
JW
D000595:Amino Acid Sequence; D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D000075065:Elongin; D007313:Insecta; D007930:Leucine / Q000737:chemistry*; D008025:Ligases / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism
D002352:Carrier Proteins; D018076:DNA, Complementary; C000616397:ELOA protein, human; C000616404:Eloa protein, rat; D000075065:Elongin; C434056:LRRC41 protein, human; D008565:Membrane Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D014452:Ubiquitins; C577447:CDC34 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; C121021:WSB1 protein, Fugu rubripes; D008025:Ligases; D007930:Leucine