Tolerance of deregulated G1/S transcription depends on critical G1/S regulon genes to prevent catastrophic genome instability.
Expression of a G1/S regulon of genes that are required for DNA replication is a ubiquitous mechanism for controlling cell proliferation; moreover, the pathological deregulated expression of E2F-regulated G1/S genes is found in every type of cancer. Cellular tolerance of deregulated G1/S transcription is surprising because this regulon includes many ... dosage-sensitive proteins. Here, we used the fission yeast Schizosaccharomyces pombe to investigate this issue. We report that deregulating the MBF G1/S regulon by eliminating the Nrm1 corepressor increases replication errors. Homology-directed repair proteins, including MBF-regulated Ctp1(CtIP), are essential to prevent catastrophic genome instability. Surprisingly, the normally inconsequential MBF-regulated S-phase cyclin Cig2 also becomes essential in the absence of Nrm1. This requirement was traced to cyclin-dependent kinase inhibition of the MBF-regulated Cdc18(Cdc6) replication origin-licensing factor. Collectively, these results establish that, although deregulation of G1/S transcription is well tolerated by cells, nonessential G1/S target genes become crucial for preventing catastrophic genome instability.
Mesh Terms:
Cell Cycle Proteins, Cyclin B, DNA-Binding Proteins, G1 Phase Cell Cycle Checkpoints, Genes, Fungal, Genomic Instability, Regulon, Repressor Proteins, Schizosaccharomyces, Schizosaccharomyces pombe Proteins, Transcription Factors
Cell Cycle Proteins, Cyclin B, DNA-Binding Proteins, G1 Phase Cell Cycle Checkpoints, Genes, Fungal, Genomic Instability, Regulon, Repressor Proteins, Schizosaccharomyces, Schizosaccharomyces pombe Proteins, Transcription Factors
Cell Rep
Date: Dec. 24, 2014
PubMed ID: 25533348
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