Werner's syndrome protein is phosphorylated in an ATR/ATM-dependent manner following replication arrest and DNA damage induced during the S phase of the cell cycle

Werner's syndrome (WS) is a rare autosomal recessive disorder that arises as a consequence of mutations in a gene coding for a protein that is a member of RecQ family of DNA helicases, WRN. The cellular function of WRN is still unclear, but on the basis of the cellular phenotypes of WS and of RecQ yeast mutants, its possible role in controlling recombination and/or in maintenance of genomic integrity during S-phase has been envisaged. With the use of two drugs, camptothecin and hydroxyurea, which produce replication-associated DNA damage and/or inhibit replication fork progression, we find that WS cells have a slower rate of repair associated with DNA damage induced in the S-phase and a reduced induction of RAD51 foci. As a consequence, WS cells undergo apoptotic cell death more than normal cells, even if they arrest and resume DNA synthesis at an apparently normal rate. Furthermore, we report that WS cells show a higher background level of DNA strand breaks and an elevated spontaneous induction of RAD51 foci. Our findings support the hypothesis that WRN could be involved in the correct resolution of recombinational intermediates that arise from replication arrest due to either DNA damage or replication fork collapse.

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Phosphorylation of FANCD2 on Two Novel Sites Is Required for Mitomycin C Resistance

Molecular and Cellular Biology ◽

10.1128/mcb.02018-05 ◽

2006 ◽

Vol 26 (18) ◽

pp. 7005-7015 ◽

Cited By ~ 80

Author(s):

Gary P. H. Ho ◽

Steven Margossian ◽

Toshiyasu Taniguchi ◽

Alan D. D'Andrea

Keyword(s):

Cell Cycle ◽

Dna Damage ◽

S Phase ◽

Cell Cycle Checkpoint ◽

Cross Linking ◽

Dependent Manner ◽

Functional Connection ◽

Cellular Resistance ◽

Checkpoint Kinase ◽

S Phase Checkpoint

ABSTRACT The Fanconi anemia (FA) pathway is a DNA damage-activated signaling pathway which regulates cellular resistance to DNA cross-linking agents. Cloned FA genes and proteins cooperate in this pathway, and monoubiquitination of FANCD2 is a critical downstream event. The cell cycle checkpoint kinase ATR is required for the efficient monoubiquitination of FANCD2, while another checkpoint kinase, ATM, directly phosphorylates FANCD2 and controls the ionizing radiation (IR)-inducible intra-S-phase checkpoint. In the present study, we identify two novel DNA damage-inducible phosphorylation sites on FANCD2, threonine 691 and serine 717. ATR phosphorylates FANCD2 on these two sites, thereby promoting FANCD2 monoubiquitination and enhancing cellular resistance to DNA cross-linking agents. Phosphorylation of the sites is required for establishment of the intra-S-phase checkpoint response. IR-inducible phosphorylation of threonine 691 and serine 717 is also dependent on ATM and is more strongly impaired when both ATM and ATR are knocked down. Threonine 691 is phosphorylated during normal S-phase progression in an ATM-dependent manner. These findings further support the functional connection of ATM/ATR kinases and FANCD2 in the DNA damage response and support a role for the FA pathway in the coordination of the S phase of the cell cycle.

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Werner's syndrome protein (WRN) migrates Holliday junctions and co‐localizes with RPA upon replication arrest

EMBO Reports ◽

10.1093/embo-reports/kvd004 ◽

2000 ◽

Vol 1 (1) ◽

pp. 80-84 ◽

Cited By ~ 246

Author(s):

Angelos Constantinou ◽

Madalena Tarsounas ◽

Julia K Karow ◽

Robert M Brosh ◽

Vilhelm A Bohr ◽

...

Keyword(s):

Holliday Junctions ◽

Werner’S Syndrome ◽

Replication Arrest ◽

Werner's Syndrome ◽

Syndrome Protein

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Prolongation of S phase and whole cell cycle in Werner's syndrome fibroblasts

Experimental Gerontology ◽

10.1016/s0531-5565(82)80009-0 ◽

1982 ◽

Vol 17 (6) ◽

pp. 473-480 ◽

Cited By ~ 46

Author(s):

F TAKEUCHI ◽

F HANAOKA ◽

M GOTO ◽

M YAMADA ◽

T MIYAMOTO

Keyword(s):

Cell Cycle ◽

S Phase ◽

Whole Cell ◽

Werner’S Syndrome ◽

Werner's Syndrome

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Regulation of DNA Replication Licensing and Re-Replication by Cdt1

International Journal of Molecular Sciences ◽

10.3390/ijms22105195 ◽

2021 ◽

Vol 22 (10) ◽

pp. 5195

Author(s):

Hui Zhang

Keyword(s):

Cell Cycle ◽

Dna Damage ◽

Dna Replication ◽

Genome Stability ◽

E3 Ligase ◽

S Phase ◽

Replication Initiation ◽

Nuclear Antigen ◽

Repair Synthesis ◽

Ubiquitin E3 Ligase

In eukaryotic cells, DNA replication licensing is precisely regulated to ensure that the initiation of genomic DNA replication in S phase occurs once and only once for each mitotic cell division. A key regulatory mechanism by which DNA re-replication is suppressed is the S phase-dependent proteolysis of Cdt1, an essential replication protein for licensing DNA replication origins by loading the Mcm2-7 replication helicase for DNA duplication in S phase. Cdt1 degradation is mediated by CRL4Cdt2 ubiquitin E3 ligase, which further requires Cdt1 binding to proliferating cell nuclear antigen (PCNA) through a PIP box domain in Cdt1 during DNA synthesis. Recent studies found that Cdt2, the specific subunit of CRL4Cdt2 ubiquitin E3 ligase that targets Cdt1 for degradation, also contains an evolutionarily conserved PIP box-like domain that mediates the interaction with PCNA. These findings suggest that the initiation and elongation of DNA replication or DNA damage-induced repair synthesis provide a novel mechanism by which Cdt1 and CRL4Cdt2 are both recruited onto the trimeric PCNA clamp encircling the replicating DNA strands to promote the interaction between Cdt1 and CRL4Cdt2. The proximity of PCNA-bound Cdt1 to CRL4Cdt2 facilitates the destruction of Cdt1 in response to DNA damage or after DNA replication initiation to prevent DNA re-replication in the cell cycle. CRL4Cdt2 ubiquitin E3 ligase may also regulate the degradation of other PIP box-containing proteins, such as CDK inhibitor p21 and histone methylase Set8, to regulate DNA replication licensing, cell cycle progression, DNA repair, and genome stability by directly interacting with PCNA during DNA replication and repair synthesis.

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A protein synthesis-dependent increase in E2F1 mRNA correlates with growth regulation of the dihydrofolate reductase promoter.

Molecular and Cellular Biology ◽

10.1128/mcb.13.3.1610 ◽

1993 ◽

Vol 13 (3) ◽

pp. 1610-1618 ◽

Cited By ~ 178

Author(s):

J E Slansky ◽

Y Li ◽

W G Kaelin ◽

P J Farnham

Keyword(s):

Cell Cycle ◽

Protein Synthesis ◽

Phase Boundary ◽

Dihydrofolate Reductase ◽

Transcription Initiation ◽

Growth Regulation ◽

Cellular Proliferation ◽

Protein S ◽

S Phase ◽

Dependent Manner

Enhanced expression of genes involved in nucleotide biosynthesis, such as dihydrofolate reductase (DHFR), is a hallmark of entrance into the DNA synthesis (S) phase of the mammalian cell cycle. To investigate the regulated expression of the DHFR gene, we stimulated serum-starved NIH 3T3 cells to synchronously reenter the cell cycle. Our previous results show that a cis-acting element at the site of DHFR transcription initiation is necessary for serum regulation. Recently, this element has been demonstrated to bind the cloned transcription factor E2F. In this study, we focused on the role of E2F in the growth regulation of DHFR. We demonstrated that a single E2F site, in the absence or presence of other promoter elements, was sufficient for growth-regulated promoter activity. Next, we showed that the increase in DHFR mRNA at the G1/S-phase boundary required protein synthesis, raising the possibility that a protein(s) lacking in serum-starved cells is required for DHFR transcription. We found that, similar to DHFR mRNA expression, levels of murine E2F1 mRNA were low in serum-starved cells and increased at the G1/S-phase boundary in a protein synthesis-dependent manner. Furthermore, in a cotransfection experiment, expression of human E2F1 stimulated the DHFR promoter 22-fold in serum-starved cells. We suggest that E2F1 may be the key protein required for DHFR transcription that is absent in serum-starved cells. Expression of E2F also abolished the serum-stimulated regulation of the DHFR promoter and resulted in transcription patterns similar to those seen with expression of the adenoviral oncoprotein E1A. In summary, we provide evidence for the importance of E2F in the growth regulation of DHFR and suggest that alterations in the levels of E2F may have severe consequences in the control of cellular proliferation.

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SPK1 is an essential S-phase-specific gene of Saccharomyces cerevisiae that encodes a nuclear serine/threonine/tyrosine kinase

Molecular and Cellular Biology ◽

10.1128/mcb.13.9.5829-5842.1993 ◽

1993 ◽

Vol 13 (9) ◽

pp. 5829-5842

Author(s):

P Zheng ◽

D S Fay ◽

J Burton ◽

H Xiao ◽

J L Pinkham ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Cell Cycle ◽

Dna Damage ◽

Dna Synthesis ◽

Genomic Library ◽

Excision Repair ◽

Low Frequency ◽

S Phase ◽

Upstream Region ◽

Specific Gene

SPK1 was originally discovered in an immunoscreen for tyrosine-protein kinases in Saccharomyces cerevisiae. We have used biochemical and genetic techniques to investigate the function of this gene and its encoded protein. Hybridization of an SPK1 probe to an ordered genomic library showed that SPK1 is adjacent to PEP4 (chromosome XVI L). Sporulation of spk1/+ heterozygotes gave rise to spk1 spores that grew into microcolonies but could not be further propagated. These colonies were greatly enriched for budded cells, especially those with large buds. Similarly, eviction of CEN plasmids bearing SPK1 from cells with a chromosomal SPK1 disruption yielded viable cells with only low frequency. Spk1 protein was identified by immunoprecipitation and immunoblotting. It was associated with protein-Ser, Thr, and Tyr kinase activity in immune complex kinase assays. Spk1 was localized to the nucleus by immunofluorescence. The nucleotide sequence of the SPK1 5' noncoding region revealed that SPK1 contains two MluI cell cycle box elements. These elements confer S-phase-specific transcription to many genes involved in DNA synthesis. Northern (RNA) blotting of synchronized cells verified that the SPK1 transcript is coregulated with other MluI box-regulated genes. The SPK1 upstream region also includes a domain highly homologous to sequences involved in induction of RAD2 and other excision repair genes by agents that induce DNA damage. spk1 strains were hypersensitive to UV irradiation. Taken together, these findings indicate that SPK1 is a dual-specificity (Ser/Thr and Tyr) protein kinase that is essential for viability. The cell cycle-dependent transcription, presence of DNA damage-related sequences, requirement for UV resistance, and nuclear localization of Spk1 all link this gene to a crucial S-phase-specific role, probably as a positive regulator of DNA synthesis.

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Xanthohumol Induces Growth Inhibition and Apoptosis in Ca Ski Human Cervical Cancer Cells

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2015/921306 ◽

2015 ◽

Vol 2015 ◽

pp. 1-10 ◽

Cited By ~ 13

Author(s):

Wai Kuan Yong ◽

Sri Nurestri Abd Malek

Keyword(s):

Cell Cycle ◽

Cervical Cancer ◽

Cancer Cells ◽

Cancer Cell ◽

Morphological Changes ◽

S Phase ◽

Phase Cell ◽

Cervical Cancer Cell Line ◽

Dependent Manner ◽

Cervical Cancer Cells

We investigate induction of apoptosis by xanthohumol on Ca Ski cervical cancer cell line. Xanthohumol is a prenylated chalcone naturally found in hop plants, previously reported to be an effective anticancer agent in various cancer cell lines. The present study showed that xanthohumol was effective to inhibit proliferation of Ca Ski cells based on IC50values using sulforhodamine B (SRB) assay. Furthermore, cellular and nuclear morphological changes were observed in the cells using phase contrast microscopy and Hoechst/PI fluorescent staining. In addition, 48-hour long treatment with xanthohumol triggered externalization of phosphatidylserine, changes in mitochondrial membrane potential, and DNA fragmentation in the cells. Additionally, xanthohumol mediated S phase arrest in cell cycle analysis and increased activities of caspase-3, caspase-8, and caspase-9. On the other hand, Western blot analysis showed that the expression levels of cleaved PARP, p53, and AIF increased, while Bcl-2 and XIAP decreased in a dose-dependent manner. Taken together, these findings indicate that xanthohumol-induced cell death might involve intrinsic and extrinsic apoptotic pathways, as well as downregulation of XIAP, upregulation of p53 proteins, and S phase cell cycle arrest in Ca Ski cervical cancer cells. This work suggests that xanthohumol is a potent chemotherapeutic candidate for cervical cancer.

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Hect E3 ubiquitin ligase Tom1 controls Dia2 degradation during the cell cycle

Molecular Biology of the Cell ◽

10.1091/mbc.e12-07-0548 ◽

2012 ◽

Vol 23 (21) ◽

pp. 4203-4211 ◽

Cited By ~ 9

Author(s):

Dong-Hwan Kim ◽

Deanna M. Koepp

Keyword(s):

Cell Cycle ◽

Protein Degradation ◽

Ubiquitin Ligase ◽

E3 Ubiquitin Ligase ◽

S Phase ◽

Temperature Sensitive ◽

Dependent Manner ◽

Charged Residues ◽

Phase Progression ◽

Positively Charged

The ubiquitin proteasome system plays a pivotal role in controlling the cell cycle. The budding yeast F-box protein Dia2 is required for genomic stability and is targeted for ubiquitin-dependent degradation in a cell cycle–dependent manner, but the identity of the ubiquitination pathway is unknown. We demonstrate that the Hect domain E3 ubiquitin ligase Tom1 is required for Dia2 protein degradation. Deletion of DIA2 partially suppresses the temperature-sensitive phenotype of tom1 mutants. Tom1 is required for Dia2 ubiquitination and degradation during G1 and G2/M phases of the cell cycle, whereas the Dia2 protein is stabilized during S phase. We find that Tom1 binding to Dia2 is enhanced in G1 and reduced in S phase, suggesting a mechanism for this proteolytic switch. Tom1 recognizes specific, positively charged residues in a Dia2 degradation/NLS domain. Loss of these residues blocks Tom1-mediated turnover of Dia2 and causes a delay in G1–to–S phase progression. Deletion of DIA2 rescues a delay in the G1–to–S phase transition in the tom1Δ mutant. Together our results suggest that Tom1 targets Dia2 for degradation during the cell cycle by recognizing positively charged residues in the Dia2 degradation/NLS domain and that Dia2 protein degradation contributes to G1–to–S phase progression.

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