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Nat Cell Biol 2010 May 01;125:484-91. doi: 10.1038/ncb2050.
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GEMC1 is a TopBP1-interacting protein required for chromosomal DNA replication.

Balestrini A , Cosentino C , Errico A , Garner E , Costanzo V .

Many of the factors required for chromosomal DNA replication have been identified in unicellular eukaryotes. However, DNA replication is poorly understood in multicellular organisms. Here, we report the identification of GEMC1 (geminin coiled-coil containing protein 1), a novel vertebrate protein required for chromosomal DNA replication. GEMC1 is highly conserved in vertebrates and is preferentially expressed in proliferating cells. Using Xenopus laevis egg extract we show that Xenopus GEMC1 (xGEMC1) binds to the checkpoint and replication factor TopBP1, which promotes binding of xGEMC1 to chromatin during pre-replication complex (pre-RC) formation. We demonstrate that xGEMC1 interacts directly with replication factors such as Cdc45 and the kinase Cdk2-CyclinE, through which it is heavily phosphorylated. Phosphorylated xGEMC1 stimulates initiation of DNA replication, whereas depletion of xGEMC1 prevents the onset of DNA replication owing to the impairment of Cdc45 loading onto chromatin. Similarly, inhibition of GEMC1 expression with morpholino and siRNA oligos prevents DNA replication in embryonic and somatic vertebrate cells. These data suggest that GEMC1 promotes initiation of chromosomal DNA replication in multicellular organisms by mediating TopBP1- and Cdk2-dependent recruitment of Cdc45 onto replication origins.

PubMed ID: 20383140
PMC ID: PMC2875115
Article link: Nat Cell Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: btg3 ccne1 cdc45 cdk2 gem gins4 gmnc gmnn mbp mcm7 orc1 parp1 topbp1 znrd2
Morpholinos: gmnc MO1 gmnc MO2

Article Images: [+] show captions
References [+] :
Blow, Initiation of DNA replication in nuclei and purified DNA by a cell-free extract of Xenopus eggs. 1986, Pubmed, Xenbase