The human ubiquitin-conjugating enzyme Cdc34 controls cellular proliferation through regulation of p27Kip1 protein levels.
Ubiquitin-mediated degradation of the cyclin-dependent kinase inhibitor p27Kip1 was shown to be required for the activation of key cyclin-dependent kinases, thereby triggering the onset of DNA replication and cell cycle progression. Although the SCFSkp2 ubiquitin ligase has been reported to mediate p27Kip1 degradation, the nature of the human ubiquitin-conjugating enzyme involved in this process has not yet been determined at the cellular level. Here, we show that antisense oligonucleotides targeting the human ubiquitin-conjugating enzyme Cdc34 downregulate its expression, inhibit the degradation of p27Kip1, and prevent cellular proliferation. Elevation of p27Kip1 protein level is found to be the sole requirement for the inhibition of cellular proliferation induced upon downregulation of Cdc34. Indeed, reducing the expression of p27Kip1 with a specific antisense oligonucleotide is sufficient to reverse the anti-proliferative phenotype elicited by the Cdc34 antisense. Furthermore, downregulation of Cdc34 is found to specifically increase the abundance of the SCFSkp2) ubiquitin ligase substrate p27Kip1, but has no concomitant effect on the level of IkBalpha and beta-catenin, which are known substrates of a closely related SCF ligase.
Butz
Nicole
N
Novartis Institutes for BioMedical Research, Novartis Pharma AG, Disease Area Oncology, CH-4002 Basel, Switzerland.
Ruetz
Stephan
S
Natt
Francois
F
Hall
Jonathan
J
Weiler
Jan
J
Mestan
Jürgen
J
Ducarre
Monique
M
Grossenbacher
Rita
R
Hauser
Patrick
P
Kempf
Dominique
D
Hofmann
Francesco
F
D064173:Anaphase-Promoting Complex-Cyclosome; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D002460:Cell Line; D049109:Cell Proliferation; D050760:Cyclin-Dependent Kinase Inhibitor p27; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000378:metabolism*
C436291:CDKN1B protein, human; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D011994:Recombinant Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C577447:CDC34 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome