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Updated: Aug 8, 2026
Analysis of Cell Cycle Position in Mammalian Cells
Published on: January 21, 2012
Cyclin A and the retinoblastoma gene product complex with a common transcription factor
L R Bandara1, J P Adamczewski, T Hunt
1Laboratory of Eukaryotic Molecular Genetics, MRC National Institute for Medical Research, Mill Hill, London, UK.
Abstract:
The retinoblastoma gene (Rb) product is a negative regulator of cellular proliferation, an effect that could be mediated in part at the transcriptional level through its ability to complex with the sequence-specific transcription factor DRTF1. This interaction is modulated by adenovirus E1a, which sequesters the Rb protein and several other cellular proteins, including cyclin A, a molecule that undergoes cyclical accumulation and destruction during each cell cycle and which is required for cell cycle progression. Cyclin A, which also complexes with DRTF1, facilitates the efficient assembly of the Rb protein into the complex. This suggests a role for cyclin A in regulating transcription and defines a transcription factor through which molecules that regulate the cell cycle in a negative fashion, such as Rb, and in a positive fashion, such as cyclin A, interact. Mutant loss-of-function Rb alleles, which occur in a variety of tumour cells, also fail to complex with E1a and large T antigen. Here we report on a naturally occurring loss-of-function Rb allele encoding a protein that fails to complex with DRTF1. This might explain how mutation in the Rb gene prevents negative growth control.
Insights
The retinoblastoma gene (Rb) protein regulates cell growth by interacting with transcription factor DRTF1. A newly identified Rb mutation prevents this interaction, potentially explaining uncontrolled cell proliferation in tumors.
Area of Science:
- Molecular Biology
- Cell Cycle Regulation
- Cancer Genetics
Background:
- The retinoblastoma gene (Rb) product functions as a negative regulator of cellular proliferation.
- Rb's growth-inhibitory effects are partly mediated transcriptionally via complex formation with the transcription factor DRTF1.
- Adenovirus E1a protein modulates this interaction by sequestering Rb and other cellular proteins, including cyclin A.
Purpose of the Study:
- To investigate the molecular mechanisms underlying retinoblastoma gene function in cell cycle regulation.
- To identify how mutations in the Rb gene contribute to tumor formation.
- To elucidate the role of cyclin A in the interaction between Rb and DRTF1.
Main Methods:
- Analysis of protein-protein interactions involving Rb, DRTF1, and adenovirus E1a.
- Characterization of a naturally occurring loss-of-function Rb allele.
- Assessment of the impact of the Rb mutation on complex formation with DRTF1.
Main Results:
- Cyclin A facilitates the assembly of the Rb protein into the DRTF1 complex, suggesting a role in transcriptional regulation.
- A naturally occurring loss-of-function Rb allele was identified that prevents complex formation with DRTF1.
- This failure to complex with DRTF1 by the mutant Rb protein may explain the loss of negative growth control observed in tumors.
Conclusions:
- Cyclin A plays a crucial role in mediating the interaction between the cell cycle regulators Rb and DRTF1.
- The study identifies a specific molecular defect in a naturally occurring Rb mutation, linking it to impaired transcriptional regulation and tumor development.
- Understanding these interactions provides insights into the mechanisms of cell cycle control and cancer pathogenesis.
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The first-ever tumor suppressor gene called Rb was identified in retinoblastoma - a rare eye tumor in children. In inherited forms of the disease, a child inherits one defective copy of the Rb gene, which predisposes them to retinoblastoma. However,...
01:20The Retinoblastoma Gene
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