GO:2000045 regulation of G1/S transition of mitotic cell cycle: Cell Cycle Control Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:2000045 describes any signaling pathway that modulates cyclin-dependent protein kinase activity to control 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, which phosphorylate RB1 and unleash E2F-dependent transcription.
• Mitochondrial hyperfusion at the G1-S boundary is required for cyclin E accumulation and S-phase entry, linking organelle dynamics to cell cycle control.
• Cell-cell and cell-matrix mechanical forces regulate G1/S progression, integrating tissue architecture with proliferation decisions.
• APC/C-Cdh1 and SCF-Skp2 form an oscillating destruction wave that controls G1/S regulators such as p27 and cyclin E.
• Dysregulation of G1/S control is a hallmark of melanoma and many cancers, making this pathway a major therapeutic target.
Description
The G1/S transition is the point of no return in the mitotic cell cycle, where a cell commits to replicating its DNA. GO:2000045, regulation of G1/S transition of mitotic cell cycle, captures the signaling pathways that modulate cyclin-dependent protein kinase (CDK) activity to govern this commitment. This term is essential for researchers because the G1/S checkpoint integrates growth signals, metabolic status, mechanical cues, and developmental programs to decide whether a cell divides or pauses. Understanding GO:2000045 helps explain how normal tissues maintain homeostasis and how cancer cells bypass proliferation controls. The regulation of G1/S is not a single event but a network of CDK complexes, transcription factors, ubiquitin ligases, and organelle dynamics that together time S-phase entry. Because many oncogenes and tumor suppressors converge on this transition, it remains one of the most studied processes in cell biology and drug discovery. This article synthesizes the QuickGO definition and verified literature to provide a research-grade overview of GO:2000045, its genes, mechanisms, disease links, and experimental models.
regulation of G1/S transition of mitotic cell cycle At A Glance
| GO ID | GO:2000045 |
|---|---|
| GO term | regulation of G1/S transition of mitotic cell cycle |
| Ontology | biological_process |
| Synonym | none |
| Major function | Modulation of cyclin-dependent protein kinase activity to control entry into S phase |
| Key CDK complexes | CDK4/6-cyclin D and CDK2-cyclin E |
| Key substrates | RB1, p27, cyclin E |
| Upstream regulators | Mitogenic signaling, mechanical forces, mitochondrial dynamics |
| Disease relevance | Cancer, melanoma, developmental disorders |
What Is GO:2000045?
GO:2000045 is defined as any signaling pathway that modulates 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 other words, it encompasses all regulatory inputs that either promote or restrain CDK activity at the G1/S boundary, thereby controlling whether a cell initiates DNA replication.
Why Is regulation of G1/S transition of mitotic cell cycle Important in Cell Biology?
Regulation of the G1/S transition is fundamental to cell proliferation, and its dysregulation is a common feature of cancer and other proliferative disorders. Because this transition integrates diverse signals, it serves as a central hub for growth control and a prime target for therapeutic intervention. Understanding GO:2000045 also illuminates how cells coordinate organelle dynamics, such as mitochondrial hyperfusion, with cell cycle progression.
• Controls the commitment point for DNA replication and cell division.
• Integrates mitogenic, metabolic, and mechanical signals.
• Dysregulated in melanoma and many other cancers.
• Involves ubiquitin ligases APC/C-Cdh1 and SCF-Skp2 that time G1/S regulators.
• Requires mitochondrial hyperfusion for cyclin E buildup and S-phase entry.
• Affects fertility through meiotic initiation in spermatogenic cells.
• Links cell cycle to sphingolipid synthesis via Swi4 in yeast.
• Provides targets for CDK4/6 inhibitors in cancer therapy.
• Influences tissue architecture through cell-cell and cell-matrix forces.
• Relevant to developmental disorders and testicular toxicity.
What Happens During regulation of G1/S transition of mitotic cell cycle?
CDK4/6-Cyclin D Activation and RB1 Phosphorylation
In simple terms: Growth signals turn on the first set of CDKs that push the cell toward DNA replication.
In early G1, mitogenic signals induce cyclin D expression, which activates CDK4 and CDK6. These kinases initiate phosphorylation of the retinoblastoma protein RB1, partially inactivating its repressive function. This step is a key node in GO:2000045 because it sets the stage for subsequent CDK2 activity and E2F release.
CDK2-Cyclin E Feedback and E2F Activation
In simple terms: A second CDK complex locks in the decision to copy DNA.
Once RB1 is partially phosphorylated, E2F transcription factors induce cyclin E, which partners with CDK2. CDK2-cyclin E further phosphorylates RB1, creating a positive feedback loop that fully releases E2F and commits the cell to S phase. This amplification is central to the regulation of G1/S transition.
Mitochondrial Hyperfusion and Cyclin E Buildup
In simple terms: The cell's power plants fuse together to help accumulate the protein needed for DNA replication.
A hyperfused mitochondrial state is achieved at the G1-S boundary and is required for cyclin E buildup and entry into S phase. This links mitochondrial dynamics to the regulation of G1/S transition, showing that organelle morphology can modulate CDK activity.
Mechanical Force Regulation of G1/S Progression
In simple terms: Physical forces from neighboring cells and the matrix influence whether a cell divides.
Cell-cell and cell-matrix forces regulate cell cycle progression, including the G1/S transition. These mechanical cues are integrated into the signaling pathways that control CDK activity, demonstrating that GO:2000045 responds to the physical environment.
Ubiquitin Ligase Waves and G1/S Timing
In simple terms: Protein destruction machines oscillate to keep the cell cycle on schedule.
APC/C-Cdh1 and SCF-Skp2 form opposing destruction waves that regulate G1/S regulators such as p27 and cyclin E. This ubiquitin-mediated control ensures proper timing of the G1/S transition and is an integral part of GO:2000045.
Key Genes Involved in GO:2000045 regulation of G1/S transition of mitotic cell cycle
The following genes and proteins are central to the regulation of the G1/S transition of the mitotic cell cycle (GO:2000045).
| Gene | Major Role | Research Relevance |
|---|---|---|
| CDK4 | Phosphorylates RB1 in early G1 | Target of CDK4/6 inhibitors in cancer |
| CDK6 | Phosphorylates RB1 in early G1 | Target of CDK4/6 inhibitors in cancer |
| CCND1 | Cyclin D, activates CDK4/6 | Overexpressed in many cancers |
| CDK2 | Phosphorylates RB1 in late G1 | Key driver of S-phase entry |
| CCNE1 | Cyclin E, activates CDK2 | Amplified in cancers, regulates G1/S |
| RB1 | Tumor suppressor, represses E2F | Inactivated in many cancers |
| E2F1 | Transcription factor released by RB1 phosphorylation | Drives S-phase gene expression |
| CDKN1B | p27, CDK inhibitor | Regulated by SCF-Skp2 |
| SKP2 | SCF ligase subunit, degrades p27 | Controls G1/S timing |
| CDH1 | APC/C activator, degrades cyclin E | Opposes SCF-Skp2 |
| AMBRA1 | Regulates mitotic spindle orientation | Phosphorylated by CDK1 and PLK1 |
| SWI4 | G1/S transcription factor in yeast | Regulates sphingolipid synthesis |
| PLK1 | Mitotic kinase, phosphorylates AMBRA1 | Links G1/S to mitosis |
| CDK1 | Mitotic CDK, phosphorylates AMBRA1 | Regulates spindle orientation |
| MCM2 | DNA replication licensing factor | Marker of S-phase entry |
| ORC1 | Origin recognition complex | Initiates DNA replication |
| CDC6 | Replication licensing | Regulated at G1/S |
How Is regulation of G1/S transition of mitotic cell cycle Regulated?
The regulation of G1/S transition is controlled by multiple layers. Mitogenic signaling induces cyclin D and CDK4/6 activity, while CDK inhibitors such as p27 are degraded by SCF-Skp2. APC/C-Cdh1 provides an opposing wave that degrades cyclin E, ensuring proper timing. Mechanical forces from the microenvironment also modulate G1/S progression. Additionally, mitochondrial hyperfusion is required for cyclin E accumulation, linking metabolic and organelle states to cell cycle control. In yeast, the G1/S transcription factor Swi4 regulates sphingolipid synthesis, showing conservation of G1/S control over lipid metabolism.
regulation of G1/S transition of mitotic cell cycle and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CDK4 | Melanoma, cancer | Knockout or point-mutation cell lines |
| RB1 | Retinoblastoma, cancer | Knockout in cancer cell lines |
| CCND1 | Cancer, proliferation | Overexpression in cell models |
| AMBRA1 | Spindle orientation, developmental disorders | Point-mutation knock-in |
| SKP2 | Cancer, G1/S timing | Knockout in cancer cells |
Cancer and Melanoma
Dysregulation of the G1/S transition is a hallmark of cancer. In melanoma, alterations in CDK4, CDK6, cyclin D, and RB1 drive uncontrolled proliferation, making this pathway a therapeutic target. CDK4/6 inhibitors have shown clinical benefit in melanoma and other cancers.
Testicular Developmental Disorder
Prenatal and postnatal exposure to polystyrene microplastics induces testis developmental disorder and affects male fertility in mice. Although the direct link to GO:2000045 is not established in this study, cell cycle regulation is critical for testicular development and spermatogenesis.
Meiotic Initiation and Fertility
Destabilization of mRNAs enhances competence to initiate meiosis in mouse spermatogenic cells. This process is tightly linked to cell cycle transitions, including the G1/S-like switch that precedes meiosis, highlighting the importance of GO:2000045 in fertility.
Mitotic Spindle Orientation and Tissue Architecture
AMBRA1 phosphorylation by CDK1 and PLK1 regulates mitotic spindle orientation. Proper spindle orientation is essential for tissue organization, and its dysregulation can contribute to developmental disorders and cancer.
From regulation of G1/S transition of mitotic cell cycle-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of CDK4 block G1/S transition? | CDK4 knockout cell line |
| Does a specific CDK4 mutation affect RB1 phosphorylation? | CDK4 point-mutation knock-in |
| Can cyclin E overexpression drive S phase? | CCNE1 overexpression |
| How does mitochondrial hyperfusion affect cyclin E? | Tagged knock-in of mitochondrial markers |
| Does mechanical force regulate G1/S? | Cell-cell and cell-matrix force models |
| What is the role of AMBRA1 phosphorylation? | AMBRA1 point-mutation knock-in |
How to Study the regulation of G1/S transition of mitotic cell cycle Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Flow cytometry | DNA content and S-phase fraction | Assess G1/S transition |
| BrdU/EdU incorporation | DNA synthesis | Measure S-phase entry |
| Western blot | Protein levels and phosphorylation | Monitor CDK activity |
| Live-cell imaging | Mitochondrial dynamics | Visualize hyperfusion at G1-S |
| CRISPR screen | Gene essentiality | Identify G1/S regulators |
| RNA-seq | Transcriptional changes | Profile E2F targets |
| Proteomics | Protein abundance and modifications | Study ubiquitin ligase substrates |
Flow Cytometry and BrdU Incorporation
Flow cytometry with BrdU or EdU labeling measures the fraction of cells entering S phase, providing a direct readout of G1/S transition. This method is widely used to assess the effects of gene knockouts or mutations on GO:2000045.
Western Blotting and Phospho-Specific Antibodies
Western blotting for phospho-RB1, cyclin E, and p27 can reveal changes in CDK activity and G1/S progression. Phospho-specific antibodies are essential to monitor the regulatory phosphorylation events central to GO:2000045.
Live-Cell Imaging of Mitochondrial Dynamics
Live-cell imaging with mitochondrial markers can visualize hyperfusion at the G1-S boundary, which is required for cyclin E buildup. This technique links organelle dynamics to cell cycle regulation.
CRISPR Screens and Transcriptomics
Genome-wide CRISPR screens combined with RNA sequencing can identify genes that regulate the G1/S transition under various conditions. These approaches are powerful for discovering novel regulators within GO:2000045.
How CRISPR Can Be Used to Study GO:2000045 regulation of G1/S transition of mitotic cell cycle
Knockout
CRISPR knockout of CDK4, CDK6, or CCND1 can block G1/S transition, confirming their essential roles in GO:2000045. Knockout cell lines are valuable for studying the consequences of losing specific regulators.
Point Mutation
Point mutations in RB1 phosphorylation sites or CDK4 catalytic residues can dissect the precise molecular events of G1/S regulation. Such models help distinguish between phosphorylation-dependent and independent functions.
Knock-in
Knock-in of tagged cyclin E or RB1 allows real-time tracking of protein dynamics at the G1/S boundary. Tagged knock-ins are also useful for studying mitochondrial hyperfusion regulators.
Overexpression
Overexpression of cyclin E or E2F1 can drive cells into S phase prematurely, providing a gain-of-function model for GO:2000045. These models are useful for testing inhibitors of the G1/S transition.
How EDITGENE Supports regulation of G1/S transition of mitotic cell cycle Research
Researchers studying regulation of G1/S transition of mitotic cell cycle-related genes often need to determine whether a candidate gene is causally involved in cell cycle control. EDITGENE provides comprehensive CRISPR services to create precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for regulation of G1/S transition of mitotic cell cycle research.
Frequently Asked Questions About regulation of G1/S transition of mitotic cell cycle
What is GO:2000045?
GO:2000045 is the Gene Ontology term for regulation of G1/S transition of mitotic cell cycle, describing signaling pathways that modulate CDK activity to control entry into S phase.
What genes are involved in regulation of G1/S transition?
Key genes include CDK4, CDK6, CCND1, CDK2, CCNE1, RB1, E2F1, CDKN1B, SKP2, and CDH1.
How is the G1/S transition regulated?
It is regulated by CDK4/6-cyclin D and CDK2-cyclin E complexes, ubiquitin ligases, mechanical forces, and mitochondrial dynamics.
Why is the G1/S transition important in cancer?
Dysregulation of G1/S control leads to uncontrolled proliferation, and CDK4/6 inhibitors are used in cancer therapy.
What methods study the G1/S transition?
Flow cytometry, BrdU incorporation, Western blotting, live-cell imaging, and CRISPR screens are commonly used.
What is the role of mitochondrial hyperfusion in G1/S?
Mitochondrial hyperfusion at the G1-S boundary is required for cyclin E buildup and S-phase entry.
How do mechanical forces affect G1/S?
Cell-cell and cell-matrix forces regulate cell cycle progression, including the G1/S transition.
What is the role of APC/C-Cdh1 in G1/S?
APC/C-Cdh1 degrades cyclin E and opposes SCF-Skp2 to time the G1/S transition.
Can CRISPR be used to study G1/S transition?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are powerful tools for studying G1/S regulators.
What diseases are linked to G1/S dysregulation?
Cancer, melanoma, testicular developmental disorders, and fertility issues are linked to G1/S dysregulation.
Conclusion
GO:2000045, regulation of G1/S transition of mitotic cell cycle, is a central biological process that integrates diverse signals to control cell proliferation. Its dysregulation is implicated in cancer, developmental disorders, and fertility defects. Understanding the genes and mechanisms of this transition is essential for both basic research and therapeutic development. EDITGENE provides comprehensive CRISPR services to facilitate precise studies of G1/S regulators.
References
- 1. Zhao T et al.. 2023. Prenatal and postnatal exposure to polystyrene microplastics induces testis developmental disorder and affects male fertility in mice.. J Hazard Mater 445:130544 PMID: 36493639
- 2. Mitra K et al.. 2009. A hyperfused mitochondrial state achieved at G1-S regulates cyclin E buildup and entry into S phase.. Proc Natl Acad Sci U S A 106(29):11960-5 PMID: 19617534
- 3. Xu W et al.. 2016. Cell Cycle Regulation and Melanoma.. Curr Oncol Rep 18(6):34 PMID: 27106898
- 4. Matos GS et al.. 2021. Regulation of sphingolipid synthesis by the G1/S transcription factor Swi4.. Biochim Biophys Acta Mol Cell Biol Lipids 1866(9):158983 PMID: 34062255
- 5. Uroz M et al.. 2018. Regulation of cell cycle progression by cell-cell and cell-matrix forces.. Nat Cell Biol 20(6):646-654 PMID: 29802405
- 6. Kurland JF et al.. 2004. Crashing waves of destruction: the cell cycle and APC(Cdh1) regulation of SCF(Skp2).. Cancer Cell 5(4):305-6 PMID: 15093536
- 7. Faienza F et al.. 2023. AMBRA1 phosphorylation by CDK1 and PLK1 regulates mitotic spindle orientation.. Cell Mol Life Sci 80(9):251 PMID: 37584777
- 8. Pfaltzgraff NG et al.. 2024. Destabilization of mRNAs enhances competence to initiate meiosis in mouse spermatogenic cells.. Development 151(14) PMID: 38884383
