Mdb1, a Fission Yeast Homolog of Human MDC1, Modulates DNA Damage Response and Mitotic Spindle Function

Cells have developed response systems to constantly monitor environmental changes and accordingly adjust growth, differentiation, and cellular stress programs. The evolutionarily conserved, nutrient-responsive, mechanistic target of rapamycin signaling (mTOR) pathway coordinates basic anabolic and catabolic cellular processes such as gene transcription, protein translation, autophagy, and metabolism, and is directly implicated in cellular and organismal aging as well as age-related diseases. mTOR mediates these processes in response to a broad range of inputs such as oxygen, amino acids, hormones, and energy levels, as well as stresses, including DNA damage. Here, we briefly summarize data relating to the interplays of the mTOR pathway with DNA damage response pathways in fission yeast, a favorite model in cell biology, and how these interactions shape cell decisions, growth, and cell-cycle progression. We, especially, comment on the roles of caffeine-mediated DNA-damage override. Understanding the biology of nutrient response, DNA damage and related pharmacological treatments can lead to the design of interventions towards improved cellular and organismal fitness, health, and survival.

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Identification of S-phase DNA damage-response targets in fission yeast reveals conservation of damage-response networks

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1525620113 ◽

2016 ◽

Vol 113 (26) ◽

pp. E3676-E3685 ◽

Cited By ~ 8

Author(s):

Nicholas A. Willis ◽

Chunshui Zhou ◽

Andrew E. H. Elia ◽

Johanne M. Murray ◽

Antony M. Carr ◽

...

Keyword(s):

Gene Expression ◽

Dna Damage ◽

Dna Replication ◽

Fission Yeast ◽

Dna Damage Response ◽

Cellular Response ◽

Genome Stability ◽

Biological Significance ◽

S Phase ◽

Damage Response

The cellular response to DNA damage during S-phase regulates a complicated network of processes, including cell-cycle progression, gene expression, DNA replication kinetics, and DNA repair. In fission yeast, this S-phase DNA damage response (DDR) is coordinated by two protein kinases: Rad3, the ortholog of mammalian ATR, and Cds1, the ortholog of mammalian Chk2. Although several critical downstream targets of Rad3 and Cds1 have been identified, most of their presumed targets are unknown, including the targets responsible for regulating replication kinetics and coordinating replication and repair. To characterize targets of the S-phase DDR, we identified proteins phosphorylated in response to methyl methanesulfonate (MMS)-induced S-phase DNA damage in wild-type, rad3∆, and cds1∆ cells by proteome-wide mass spectrometry. We found a broad range of S-phase–specific DDR targets involved in gene expression, stress response, regulation of mitosis and cytokinesis, and DNA replication and repair. These targets are highly enriched for proteins required for viability in response to MMS, indicating their biological significance. Furthermore, the regulation of these proteins is similar in fission and budding yeast, across 300 My of evolution, demonstrating a deep conservation of S-phase DDR targets and suggesting that these targets may be critical for maintaining genome stability in response to S-phase DNA damage across eukaryotes.

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Two Distinct Cdc2 Pools Regulate Cell Cycle Progression and the DNA Damage Response in the Fission Yeast S.pombe

PLoS ONE ◽

10.1371/journal.pone.0130748 ◽

2015 ◽

Vol 10 (7) ◽

pp. e0130748 ◽

Cited By ~ 14

Author(s):

Thomas Caspari ◽

Victoria Hilditch

Keyword(s):

Cell Cycle ◽

Dna Damage ◽

Fission Yeast ◽

Dna Damage Response ◽

Cell Cycle Progression ◽

Cycle Progression ◽

Damage Response ◽

Regulate Cell Cycle Progression

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A Mammalian-Like DNA Damage Response of Fission Yeast to Nucleoside Analogs

Genetics ◽

10.1534/genetics.112.145730 ◽

2012 ◽

Vol 193 (1) ◽

pp. 143-157 ◽

Cited By ~ 11

Author(s):

Sarah A. Sabatinos ◽

Tara L. Mastro ◽

Marc D. Green ◽

Susan L. Forsburg

Keyword(s):

Dna Damage ◽

Fission Yeast ◽

Dna Damage Response ◽

Nucleoside Analogs ◽

Damage Response

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Dimerization Mediated by a Divergent Forkhead-associated Domain Is Essential for the DNA Damage and Spindle Functions of Fission Yeast Mdb1

Journal of Biological Chemistry ◽

10.1074/jbc.m115.642538 ◽

2015 ◽

Vol 290 (34) ◽

pp. 21054-21066 ◽

Cited By ~ 5

Author(s):

Shukun Luo ◽

Xiaoran Xin ◽

Li-Lin Du ◽

Keqiong Ye ◽

Yi Wei

Keyword(s):

Dna Damage ◽

Fission Yeast ◽

Dna Damage Response ◽

Mammalian Cells ◽

Main Function ◽

Fha Domain ◽

Histone H2ax ◽

Terminal Domain ◽

Damage Response

MDC1 is a key factor of DNA damage response in mammalian cells. It possesses two phospho-binding domains. In its C terminus, a tandem BRCA1 C-terminal domain binds phosphorylated histone H2AX, and in its N terminus, a forkhead-associated (FHA) domain mediates a phosphorylation-enhanced homodimerization. The FHA domain of the Drosophila homolog of MDC1, MU2, also forms a homodimer but utilizes a different dimer interface. The functional importance of the dimerization of MDC1 family proteins is uncertain. In the fission yeast Schizosaccharomyces pombe, a protein sharing homology with MDC1 in the tandem BRCA1 C-terminal domain, Mdb1, regulates DNA damage response and mitotic spindle functions. Here, we report the crystal structure of the N-terminal 91 amino acids of Mdb1. Despite a lack of obvious sequence conservation to the FHA domain of MDC1, this region of Mdb1 adopts an FHA-like fold and is therefore termed Mdb1-FHA. Unlike canonical FHA domains, Mdb1-FHA lacks all the conserved phospho-binding residues. It forms a stable homodimer through an interface distinct from those of MDC1 and MU2. Mdb1-FHA is important for the localization of Mdb1 to DNA damage sites and the spindle midzone, contributes to the roles of Mdb1 in cellular responses to genotoxins and an antimicrotubule drug, and promotes in vitro binding of Mdb1 to a phospho-H2A peptide. The defects caused by the loss of Mdb1-FHA can be rescued by fusion with either of two heterologous dimerization domains, suggesting that the main function of Mdb1-FHA is mediating dimerization. Our data support that FHA-mediated dimerization is conserved for MDC1 family proteins.

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