Abstract
Geminin and its binding partner Cdt1 are essential for the regulation of DNA replication. Here we show that the CULLIN3 E3 ubiquitin ligase adaptor protein SPOP binds Geminin at endogenous level and regulates DNA replication. SPOP promotes K27-linked non-degradative poly-ubiquitination of Geminin at lysine residues 100 and 127. This poly-ubiquitination of Geminin prevents DNA replication over-firing by indirectly blocking the association of Cdt1 with the MCM protein complex, an interaction required for DNA unwinding and replication. SPOP is frequently mutated in certain human cancer types and implicated in tumorigenesis. We show that cancer-associated SPOP mutations impair Geminin K27-linked poly-ubiquitination and induce replication origin over-firing and re-replication. The replication stress caused by SPOP mutations triggers replication catastrophe and cell death upon ATR inhibition. Our results reveal a tumor suppressor role of SPOP in preventing DNA replication over-firing and genome instability and suggest that SPOP-mutated tumors may be susceptible to ATR inhibitor therapy.
Highlights
Geminin and its binding partner Cdt[1] are essential for the regulation of DNA replication
While a handful of previous studies suggest that SPOP deregulation may lead to genomic instability[41,42,43], no study has directly examined the impact of SPOP mutations on DNA replication
The The Cancer Genome Atlas (TCGA) data show that none of these genes are downregulated in SPOP-mutated prostate cancer patient samples (Supplementary Fig. 1a–d), and the mRNA levels of these genes are negatively correlated to SPOP mRNA expression in prostate cancers (Supplementary Fig. 1e-h)
Summary
Geminin and its binding partner Cdt[1] are essential for the regulation of DNA replication. SPOP promotes K27-linked non-degradative poly-ubiquitination of Geminin at lysine residues 100 and 127 This poly-ubiquitination of Geminin prevents DNA replication over-firing by indirectly blocking the association of Cdt[1] with the MCM protein complex, an interaction required for DNA unwinding and replication. Origin reactivation is a driver of gene amplification, copy number variation, and aberrant chromosome segregation[2,3] In mammalian cells, it causes chromosomal breaks and activation of the DNA damage response[4,5]. Geminin is an unstable protein that is targeted for degradation by the anaphase-promoting complex (APC)[16] Both Geminin and Cdt[1] are expressed at high levels in late S and G2 phases, where Geminin binds Cdt[1] and prevents DNA re-replication[15,17,18]
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