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Two E3 ubiquitin ligases, SCF‐Skp2 and DDB1‐Cul4, target human Cdt1 for proteolysis
Author(s) -
Nishitani Hideo,
Sugimoto Nozomi,
Roukos Vassilis,
Nakanishi Yohsuke,
Saijo Masafumi,
Obuse Chikashi,
Tsurimoto Toshiki,
Nakayama Keiichi I,
Nakayama Keiko,
Fujita Masatoshi,
Lygerou Zoi,
Nishimoto Takeharu
Publication year - 2006
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601002
Subject(s) - dna replication factor cdt1 , biology , cell division control protein 4 , ubiquitin , licensing factor , dna replication , origin recognition complex , proteolysis , microbiology and biotechnology , dna re replication , eukaryotic dna replication , replication factor c , control of chromosome duplication , skp2 , ubiquitin ligase , biochemistry , dna , gene , enzyme
Replication licensing is carefully regulated to restrict replication to once in a cell cycle. In higher eukaryotes, regulation of the licensing factor Cdt1 by proteolysis and Geminin is essential to prevent re‐replication. We show here that the N‐terminal 100 amino acids of human Cdt1 are recognized for proteolysis by two distinct E3 ubiquitin ligases during S–G2 phases. Six highly conserved amino acids within the 10 first amino acids of Cdt1 are essential for DDB1‐Cul4‐mediated proteolysis. This region is also involved in proteolysis following DNA damage. The second E3 is SCF‐Skp2, which recognizes the Cy‐motif‐mediated Cyclin E/A‐cyclin‐dependent kinase‐phosphorylated region. Consistently, in HeLa cells cosilenced of Skp2 and Cul4, Cdt1 remained stable in S–G2 phases. The Cul4‐containing E3 is active during ongoing replication, while SCF‐Skp2 operates both in S and G2 phases. PCNA binds to Cdt1 through the six conserved N‐terminal amino acids. PCNA is essential for Cul4‐ but not Skp2‐directed degradation during DNA replication and following ultraviolet‐irradiation. Our data unravel multiple distinct pathways regulating Cdt1 to block re‐replication.