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p14(ARF) regulates E2F activity
Sarah L Mason1, Oonagh Loughran, Nicholas B La Thangue
1Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Davidson Building, University of Glasgow, Glasgow G12 8QQ, UK.
Abstract:
The ARF protein product of the ink4a/arf locus is induced by a variety of oncogenic signals. ARF facilitates growth arrest through the p53 pathway by hindering the down-regulation of p53 activity mediated by MDM2, through the formation of a protein complex with MDM2. Here we have explored the possibility that human p14(ARF) activity is integrated with growth regulating pathways other than p53, and report our results that p14(ARF) can control the activity of the E2F transcription factor. p14(ARF) regulates E2F activity in different cell-types, including p53(-/-)/mdm(-/-) MEFs, thus excluding that the effects of p14(ARF) are indirectly caused through MDM2 modulation. p14(ARF) down-regulates E2F-dependent transcription, and in cells undergoing E2F-dependent apoptosis prompts cell cycle arrest. p14(ARF) possesses multiple binding domains for E2F-1, one of which resides within the N-terminal region and coincides with the regulation of E2F activity. A mutational analysis of p14(ARF) indicates that the E2F-1 and MDM2 binding domains can be distinguished. These results highlight the potential interplay between p14(ARF) and E2F, and establish p14(ARF) as a pleiotrophic regulator of cell growth that acts by targetting at least two key pathways in the control of proliferation, namely E2F and p53.
Insights
The ARF protein (Alternative Reading Frame) regulates cell growth by influencing both the p53 and E2F pathways. This study shows ARF directly controls E2F transcription factor activity, impacting cell cycle arrest.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- The ARF protein, a product of the ink4a/arf locus, is induced by oncogenic signals.
- ARF promotes cell growth arrest via the p53 pathway by inhibiting MDM2-mediated p53 downregulation.
Purpose of the Study:
- To investigate if human p14(ARF) interacts with growth-regulating pathways beyond p53.
- To determine if p14(ARF) directly influences E2F transcription factor activity.
Main Methods:
- Cell-type specific analysis including p53(-/-)/mdm(-/-) MEFs.
- Mutational analysis of p14(ARF) to distinguish binding domains.
- Assessing E2F-dependent transcription and apoptosis.
Main Results:
- p14(ARF) directly regulates E2F activity across different cell types, independent of MDM2.
- p14(ARF) down-regulates E2F-dependent transcription and induces cell cycle arrest in cells undergoing E2F-dependent apoptosis.
- Distinct binding domains for E2F-1 and MDM2 were identified on p14(ARF).
Conclusions:
- p14(ARF) acts as a pleiotropic regulator of cell growth.
- p14(ARF) targets both the E2F and p53 pathways, highlighting their interplay in proliferation control.