CDC7 and CDK8 kinases cooperate to support DNA replication origin firing in human cells.

CDK8/CCNC kinase is linked to DNA replication origin firing in human cells under CDC7 inhibition, and CDK8 depletion reduces CDC7-inhibitor–imposed DNA synthesis.

• Why it matters: Efficient origin activation is needed for DNA synthesis and genome stability, but the genes and kinases that tune this process during CDC7 blockade are not fully defined.
• What they did: The team ran a chemogenetic genome-wide CRISPR-KO screen in cells treated with the CDC7 inhibitor XL413, then clustered hits using genetic co-essentiality; they validated effects with DNA fiber assays and MCM/MTBP-dependent tests.
• The result: CDK8/CCNC clusters with replication initiation factors, and CDK8 inhibition suppresses DNA synthesis in a way that requires CDK8/CCNC binding to MTBP; CDC7 and CDK8 associate with the MCM complex and each contributes to replicative helicase phosphorylation.

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