E2-C, a cyclin-selective ubiquitin carrier protein required for the destruction of mitotic cyclins.
Ubiquitin-dependent proteolysis of the mitotic cyclins A and B is required for the completion of mitosis and entry into the next cell cycle. This process is catalyzed by the cyclosome, an approximately 22S particle that contains a cyclin-selective ubiquitin ligase activity, E3-C, that requires a cyclin-selective ubiquitin carrier protein (UBC) E2-C. Here we report the purification and cloning of E2-C from clam oocytes. The deduced amino acid sequence of E2-C indicates that it is a new UBC family member. Bacterially expressed recombinant E2-C is active in in vitro cyclin ubiquitination assays, where it exhibits the same substrate specificities seen with native E2-C. These results demonstrate that E2-C is not a homolog of UBC4 or UBC9, proteins previously suggested to be involved in cyclin ubiquitination, but is a new UBC family member with unique properties.
Aristarkhov
A
A
Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
Eytan
E
E
Moghe
A
A
Admon
A
A
Hershko
A
A
Ruderman
J V
JV
D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D002846:Chromatography, Affinity; D016213:Cyclins / Q000378:metabolism*; D017931:DNA Primers; D006801:Humans; D008025:Ligases; D008938:Mitosis; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D044763:Ubiquitin-Conjugating Enzymes; D014452:Ubiquitins / Q000378:metabolism*
D002352:Carrier Proteins; D016213:Cyclins; D017931:DNA Primers; D011994:Recombinant Proteins; D014452:Ubiquitins; C046288:ubiquitin carrier proteins; D044763:Ubiquitin-Conjugating Enzymes; D008025:Ligases