GO:2000134 negative regulation of G1/S transition of mitotic cell cycle: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:2000134 describes any signaling pathway that decreases or inhibits cyclin-dependent protein kinase (CDK) activity to block the switch from G1 phase to S phase of the mitotic cell cycle.
• The G1/S transition is driven by CDK4/6-cyclin D and CDK2-cyclin E complexes; negative regulation of GO:2000134 therefore centers on CDK inhibitors, cyclin degradation, and checkpoint phosphatases.
• Cell cycle-regulated proteolysis of mitotic target proteins is a core mechanism that enforces irreversible progression and can also restrain G1/S entry.
• DYRK family protein kinases regulate protein stability in cell cycle control, linking phosphorylation-dependent degradation to negative regulation of G1/S transition.
• Dysregulation of G1/S negative regulation is implicated in breast cancer and other malignancies, where cell cycle-related gene signatures carry prognostic value.
• CRISPR knockout, point-mutation, knock-in, and overexpression models allow causal testing of candidate negative regulators of the G1/S transition.
Description
The G1/S transition is the point at which a cell commits to replicating its DNA, and it is controlled by the opposing actions of cyclin-dependent kinases (CDKs) and their inhibitors. GO:2000134, negative regulation of G1/S transition of mitotic cell cycle, captures the signaling pathways that decrease or inhibit CDK activity to prevent or delay this switch. Because unscheduled S-phase entry is a hallmark of proliferative disease, understanding how this negative regulation is wired is central to cell cycle biology. Experimental work has shown that cell cycle-regulated proteolysis of mitotic target proteins contributes to the timing and directionality of cell cycle transitions, providing a mechanistic basis for negative control at G1/S. Network-level analyses of cell cycle regulators further indicate that relative protein abundance statistics can predict functional modules that restrain CDK activity. In parallel, DYRK family kinases have emerged as regulators of protein stability in cell cycle control, adding a phosphorylation-dependent layer to G1/S negative regulation. This article synthesizes the QuickGO definition of GO:2000134 with verified literature to describe its mechanism, key genes, disease relevance, and the CRISPR-based methods used to study it.
negative regulation of G1/S transition of mitotic cell cycle At A Glance
| GO ID | GO:2000134 |
|---|---|
| GO term | negative regulation of G1/S transition of mitotic cell cycle |
| Ontology | biological_process |
| Synonym | None listed in QuickGO |
| Major function | Decreases or inhibits cyclin-dependent protein kinase activity to modulate the G1-to-S switch of the mitotic cell cycle |
| Biological context | Cell cycle checkpoint control at the G1/S boundary |
| Key molecular players | CDKs, cyclins, CDK inhibitors, DYRK family kinases, ubiquitin-proteasome components |
| Disease relevance | Cancer and other proliferative disorders linked to cell cycle deregulation |
| Research methods | CRISPR knockout, point mutation, knock-in, overexpression, cell cycle profiling, proteomics |
What Is GO:2000134?
GO:2000134 is a biological_process term defined as any signaling pathway that decreases or inhibits the activity of a cell cycle cyclin-dependent protein kinase to modulate the switch from G1 phase to S phase of the mitotic cell cycle. In practice, this includes pathways that raise CDK inhibitor levels, promote cyclin degradation, or activate inhibitory phosphorylation of CDKs, all of which delay or prevent S-phase entry.
Why Is negative regulation of G1/S transition of mitotic cell cycle Important in Cell Biology?
Negative regulation of the G1/S transition is a fundamental safeguard that prevents premature or inappropriate DNA replication. When this control fails, cells can enter S phase with damaged or unreplicated genomes, contributing to genomic instability and cancer. Conversely, excessive negative regulation can cause quiescence or senescence, which is relevant to tissue homeostasis and aging. Because CDK4/6 inhibitors and other cell cycle-targeted therapies act at this boundary, the pathways annotated under GO:2000134 are directly relevant to drug response and resistance. Studying these pathways also clarifies how proteolysis and phosphorylation networks impose directionality on the cell cycle.
• Defines the checkpoint that prevents unscheduled S-phase entry and DNA replication stress.
• Provides the mechanistic basis for CDK inhibitor activity and cell cycle-targeted therapies.
• Links cell cycle-regulated proteolysis to irreversible progression through G1/S.
• Connects DYRK-family kinase signaling to protein stability control in the cell cycle.
• Supports prognostic gene signatures in breast cancer and other tumors.
• Enables functional dissection of cell cycle modules using relative protein abundance statistics.
• Informs studies of endoreduplication and cell cycle diversity in model organisms.
• Guides CRISPR-based causal testing of candidate negative regulators.
What Happens During negative regulation of G1/S transition of mitotic cell cycle?
CDK inhibition by CDK inhibitors
In simple terms: Brakes are applied to the enzymes that push the cell into DNA replication.
The G1/S transition is driven by CDK4/6-cyclin D and CDK2-cyclin E complexes. Negative regulation of GO:2000134 includes pathways that increase the abundance or activity of CDK inhibitors, which bind and inhibit these complexes. Network analyses of cell cycle regulators show that relative protein abundance statistics can predict modules that restrain CDK activity, supporting a quantitative model of this inhibition. Cell cycle-regulated proteolysis of mitotic target proteins further contributes to the timing of these inhibitory events.
Cyclin degradation and proteolysis
In simple terms: The accelerator proteins are destroyed so the cell cannot move forward.
Cell cycle-regulated proteolysis of mitotic target proteins is a well-established mechanism that controls the abundance of key cell cycle regulators. Degradation of cyclins and other positive regulators at the G1/S boundary prevents premature S-phase entry. DYRK family protein kinases regulate protein stability in cell cycle control, linking phosphorylation to degradation and thereby contributing to negative regulation of the G1/S transition.
Inhibitory phosphorylation of CDKs
In simple terms: A phosphate tag is added to the engine to keep it switched off.
Inhibitory phosphorylation of CDKs by kinases such as Wee1 and Myt1 keeps CDK activity low until the cell is ready to divide. Although these events are best characterized at the G2/M transition, the same logic applies at G1/S, where phosphorylation-dependent regulation of CDK activity contributes to the negative control described by GO:2000134. DYRK family kinases add an additional phosphorylation-dependent layer by regulating protein stability in cell cycle control.
Checkpoint signaling and DNA damage responses
In simple terms: If DNA is damaged, a signal stops the cell from copying it.
DNA damage checkpoints activate signaling pathways that inhibit CDK activity and delay G1/S progression. UBE2C promotes cell cycle progression and suppresses DNA damage-induced apoptosis in triple-negative breast cancer, indicating that the balance between ubiquitin-mediated degradation and checkpoint signaling is critical at this boundary. Integrated analysis of cell cycle-related genes in HR+/HER2- breast cancer further supports the clinical relevance of these checkpoint pathways.
Cell cycle diversity and context-specific regulation
In simple terms: Different cell types use slightly different brakes.
Cell cycle diversity involves differential regulation of Cyclin E activity in the Drosophila bristle cell lineage, showing that negative regulation of G1/S can be tailored to specific developmental contexts. In plants, the cotton endoreduplication gene GaTOP6B regulates trichome branching development, illustrating that G1/S control is conserved but adapted across kingdoms. The plant cell cycle literature similarly emphasizes conserved and divergent features of G1/S regulation.
Key Genes Involved in GO:2000134 negative regulation of G1/S transition of mitotic cell cycle
The following genes and proteins are central to the negative regulation of the G1/S transition of the mitotic cell cycle, based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CDK2 | Cyclin-dependent kinase driving G1/S transition; target of negative regulation | Core kinase whose inhibition defines GO:2000134 |
| CDK4 | Cyclin-dependent kinase partnering with cyclin D at G1/S | Key target of CDK4/6 inhibitors and negative regulation |
| CDK6 | Cyclin-dependent kinase partnering with cyclin D at G1/S | Therapeutic target in breast cancer |
| CCND1 | Cyclin D1, activates CDK4/6 | Positive regulator whose restraint is part of G1/S negative control |
| CCNE1 | Cyclin E, activates CDK2 | Differentially regulated in cell cycle diversity |
| CDKN1A | p21, CDK inhibitor | Mediates negative regulation of G1/S |
| CDKN1B | p27, CDK inhibitor | Restrains CDK2 activity at G1/S |
| CDKN2A | p16, CDK4/6 inhibitor | Frequently altered in cancer |
| UBE2C | Ubiquitin-conjugating enzyme promoting cell cycle progression | Suppresses DNA damage-induced apoptosis in TNBC |
| DYRK1A | DYRK family kinase regulating protein stability | Links phosphorylation to cell cycle control |
| DYRK1B | DYRK family kinase regulating protein stability | Emerging regulator of cell cycle control |
| WEE1 | Inhibitory kinase phosphorylating CDKs | Contributes to negative regulation of CDK activity |
| MYT1 | Inhibitory kinase phosphorylating CDKs | Contributes to negative regulation of CDK activity |
| CDC25A | Phosphatase activating CDKs | Counteracts negative regulation at G1/S |
| SKP2 | F-box protein mediating proteolysis of CDK inhibitors | Links proteolysis to G1/S control |
| TOP6B | Endoreduplication regulator in cotton | Illustrates G1/S control in plants |
| E2F1 | Transcription factor driving S-phase genes | Downstream target of G1/S regulation |
How Is negative regulation of G1/S transition of mitotic cell cycle Regulated?
Negative regulation of the G1/S transition is itself regulated at multiple levels. Cell cycle-regulated proteolysis of mitotic target proteins ensures that inhibitory factors are present only when needed. DYRK family protein kinases regulate protein stability in cell cycle control, providing a phosphorylation-dependent mechanism that can stabilize or destabilize key regulators. Network analyses using relative protein abundance statistics reveal that cell cycle regulators form modules whose stoichiometry determines whether the G1/S transition is permitted. In cancer, integrated analysis of cell cycle-related genes shows that expression signatures of these regulators correlate with prognosis and subtype, indicating that transcriptional and post-transcriptional layers shape the pathway. UBE2C-mediated ubiquitination further modulates the balance between progression and apoptosis in response to DNA damage.
negative regulation of G1/S transition of mitotic cell cycle and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| UBE2C | Triple-negative breast cancer progression and apoptosis resistance | CRISPR knockout in TNBC cell lines |
| CDK4 | HR+/HER2- breast cancer and CDK4/6 inhibitor response | Point mutation and knock-in models |
| CDK6 | Breast cancer proliferation | Overexpression and knockout models |
| DYRK1A | Cell cycle deregulation and proliferative disease | Knockout and point mutation models |
| CCNE1 | Cell cycle diversity and developmental proliferation | Drosophila bristle lineage models |
Breast cancer
Integrated analysis of cell cycle-related genes in HR+/HER2- breast cancer identifies signatures that stratify patients and predict outcomes, highlighting the clinical importance of G1/S negative regulation. In triple-negative breast cancer, UBE2C promotes cell cycle progression and suppresses DNA damage-induced apoptosis, suggesting that loss of negative regulation at G1/S contributes to aggressive disease.
Cell cycle deregulation in proliferative disorders
Because GO:2000134 restrains CDK activity, its failure can lead to unscheduled proliferation. Cell cycle-regulated proteolysis of mitotic target proteins is a general mechanism whose disruption can affect multiple proliferative disorders. DYRK family kinases, which regulate protein stability in cell cycle control, are increasingly implicated in diseases characterized by abnormal proliferation.
Developmental and plant biology
Cell cycle diversity involves differential regulation of Cyclin E activity in the Drosophila bristle cell lineage, showing that G1/S negative regulation is adapted to developmental contexts. In cotton, the endoreduplication gene GaTOP6B regulates trichome branching development, illustrating how G1/S control influences plant morphogenesis. The plant cell cycle literature provides a comparative framework for these mechanisms.
From negative regulation of G1/S transition of mitotic cell cycle-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is a candidate gene required for negative regulation of G1/S? | CRISPR knockout cell model |
| Does a specific phosphorylation site control CDK inhibition? | Point-mutation knock-in model |
| Does a disease-associated variant alter G1/S control? | Knock-in of the variant allele |
| Where and when is the regulator expressed? | Tagged knock-in with fluorescent or epitope tag |
| Does overexpression delay S-phase entry? | Doxycycline-inducible overexpression model |
| Which pathways cooperate to restrain CDK activity? | CRISPR library screening and bioinformatics |
How to Study the negative regulation of G1/S transition of mitotic cell cycle Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Flow cytometry | Cell cycle phase distribution | Assessing G1/S arrest after gene perturbation |
| EdU incorporation | DNA synthesis | Confirming S-phase entry blockade |
| Western blot | Protein levels of CDKs, cyclins, CDK inhibitors | Validating negative regulation |
| Cycloheximide chase | Protein half-life | Measuring proteolysis of cell cycle regulators |
| RNA-seq | Transcriptome changes | Identifying cell cycle gene signatures |
| Network module prediction | Co-regulated protein modules | Predicting negative regulators from abundance data |
| Live-cell imaging | Real-time cell cycle progression | Tracking G1/S timing in single cells |
| CRISPR library screening | Fitness and cell cycle phenotypes | Discovering novel negative regulators |
Cell cycle profiling by flow cytometry
Flow cytometry with DNA dyes and EdU incorporation measures the fraction of cells in G1, S, and G2/M, providing a direct readout of whether negative regulation of G1/S is enhanced or lost.
Proteomics and protein stability assays
Mass spectrometry-based proteomics and cycloheximide chase assays quantify the abundance and half-life of CDKs, cyclins, and CDK inhibitors, linking proteolysis to GO:2000134.
Transcriptomics and network analysis
RNA sequencing combined with network module prediction using relative protein abundance statistics identifies co-regulated cell cycle modules and candidate negative regulators.
Imaging and single-cell analysis
Live-cell imaging of fluorescently tagged cell cycle reporters and single-cell RNA sequencing reveal heterogeneity in G1/S timing and the impact of negative regulators.
How CRISPR Can Be Used to Study GO:2000134 negative regulation of G1/S transition of mitotic cell cycle
Knockout
CRISPR knockout of candidate genes such as CDKN1A, CDKN1B, or UBE2C removes the negative regulator and is expected to accelerate G1/S transition, which can be measured by flow cytometry and EdU incorporation.
Point Mutation
Point mutation of phosphorylation sites in DYRK family kinases or CDKs tests whether specific residues are required for negative regulation of G1/S, using knock-in of the mutant allele followed by cell cycle profiling.
Knock-in
Knock-in of disease-associated variants or fluorescent tags allows tracking of regulator localization and stability in isogenic backgrounds, linking genotype to G1/S phenotypes.
Overexpression
Inducible overexpression of candidate negative regulators such as CDKN1A or DYRK1B tests whether increased dosage delays or blocks S-phase entry, providing gain-of-function evidence for GO:2000134.
How EDITGENE Supports negative regulation of G1/S transition of mitotic cell cycle Research
Researchers studying negative regulation of G1/S transition of mitotic cell cycle-related genes often need to determine whether a candidate gene is causally involved in restraining CDK activity or is merely correlated with cell cycle changes. EDITGENE provides the CRISPR tools and bioinformatics support required to move from correlation to causation in cell cycle research.
Contact EDITGENE today to design your custom CRISPR model for negative regulation of G1/S transition of mitotic cell cycle research.
Frequently Asked Questions About negative regulation of G1/S transition of mitotic cell cycle
What is GO:2000134?
GO:2000134 is the Gene Ontology term for negative regulation of G1/S transition of mitotic cell cycle, defined as any signaling pathway that decreases or inhibits cyclin-dependent protein kinase activity to modulate the switch from G1 to S phase.
What genes are involved in negative regulation of the G1/S transition?
Key genes include CDK2, CDK4, CDK6, CCND1, CCNE1, CDKN1A, CDKN1B, CDKN2A, UBE2C, DYRK1A, DYRK1B, WEE1, MYT1, CDC25A, and SKP2.
How is the G1/S transition negatively regulated?
It is negatively regulated by CDK inhibitors, cyclin degradation via regulated proteolysis, inhibitory phosphorylation of CDKs, and checkpoint signaling that responds to DNA damage.
Why is negative regulation of G1/S important in cancer?
Loss of negative regulation allows unscheduled S-phase entry and genomic instability, and cell cycle gene signatures are prognostic in breast cancer.
What role do DYRK kinases play in G1/S control?
DYRK family protein kinases regulate protein stability in cell cycle control, adding a phosphorylation-dependent layer to negative regulation of G1/S.
How can CRISPR be used to study GO:2000134?
CRISPR knockout, point mutation, knock-in, and overexpression models allow causal testing of whether a candidate gene restrains CDK activity and delays S-phase entry.
What methods measure negative regulation of G1/S?
Flow cytometry, EdU incorporation, Western blot, cycloheximide chase, RNA-seq, network module prediction, live-cell imaging, and CRISPR library screening are commonly used.
Is negative regulation of G1/S conserved in plants?
Yes, plant cell cycle studies and the cotton endoreduplication gene GaTOP6B show conserved and adapted features of G1/S control.
What is the difference between positive and negative regulation of G1/S?
Positive regulation promotes CDK activity and S-phase entry, while negative regulation inhibits CDK activity and delays or prevents the transition.
Which diseases are linked to G1/S negative regulation?
Breast cancer and other proliferative disorders are linked to deregulation of G1/S negative control, with UBE2C and CDK4/6 among the relevant genes.
Conclusion
GO:2000134, negative regulation of G1/S transition of mitotic cell cycle, is a central biological process that restrains CDK activity through CDK inhibitors, regulated proteolysis, inhibitory phosphorylation, and checkpoint signaling. Its dysregulation contributes to cancer and other proliferative diseases, making it a key area for therapeutic and prognostic research. CRISPR-based knockout, point-mutation, knock-in, and overexpression models, combined with cell cycle profiling and bioinformatics, provide the tools needed to dissect these pathways causally.
References
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- 3. Lai J et al.. 2022. Integrated analysis of cell cycle-related genes in HR+/HER2- breast cancer.. Breast Cancer 29(1):121-130 PMID: 34449047
- 4. Oguz C et al.. 2017. Predicting network modules of cell cycle regulators using relative protein abundance statistics.. BMC Syst Biol 11(1):30 PMID: 28241833
- 5. Hu Q et al.. 2025. UBE2C promotes cell cycle progression and suppresses DNA damage-induced apoptosis in triple-negative breast cancer.. DNA Repair (Amst) 154:103901 PMID: 41086596
- 6. Audibert A et al.. 2005. Cell cycle diversity involves differential regulation of Cyclin E activity in the Drosophila bristle cell lineage.. Development 132(10):2287-97 PMID: 15829522
- 7. Song J et al.. 2024. A cotton endoreduplication gene, GaTOP6B, regulates trichome branching development.. Plant Physiol Biochem 214:108888 PMID: 38954944
- 8. Becker W. 2012. Emerging role of DYRK family protein kinases as regulators of protein stability in cell cycle control.. Cell Cycle 11(18):3389-94 PMID: 22918246
