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Human Geminin promotes pre‐RC formation and DNA replication by stabilizing CDT1 in mitosis
Author(s) -
Ballabeni Andrea,
Melixetian Marina,
Zamponi Raffaella,
Masiero Laura,
Marii Federica,
Helin Kristian
Publication year - 2004
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.7600314
Subject(s) - dna replication factor cdt1 , biology , microbiology and biotechnology , licensing factor , mitosis , xenopus , dna re replication , control of chromosome duplication , dna replication , origin recognition complex , pre replication complex , cell cycle , eukaryotic dna replication , cancer research , genetics , dna , cell , gene
Geminin is an unstable inhibitor of DNA replication that negatively regulates the licensing factor CDT1 and inhibits pre‐replicative complex (pre‐RC) formation in Xenopus egg extracts. Here we describe a novel function of Geminin. We demonstrate that human Geminin protects CDT1 from proteasome‐mediated degradation by inhibiting its ubiquitination. In particular, Geminin ensures basal levels of CDT1 during S phase and its accumulation during mitosis. Consistently, inhibition of Geminin synthesis during M phase leads to impairment of pre‐RC formation and DNA replication during the following cell cycle. Moreover, we show that inhibition of CDK1 during mitosis, and not Geminin depletion, is sufficient for premature formation of pre‐RCs, indicating that CDK activity is the major mitotic inhibitor of licensing in human cells. Taken together with recent data from our laboratory, our results demonstrate that Geminin is both a negative and positive regulator of pre‐RC formation in human cells, playing a positive role in allowing CDT1 accumulation in G2–M, and preventing relicensing of origins in S–G2.