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Drosophila cyclin E interacts with components of the Brahma complex
Anthony M Brumby1, Claudia B Zraly, Julie A Horsfield
1Peter MacCallum Cancer Institute, Locked bag 1, A'Beckett Street, Melbourne, Victoria 8006, Australia.
Abstract:
Cyclin E-Cdk2 is essential for S phase entry. To identify genes interacting with cyclin E, we carried out a genetic screen using a hypomorphic mutation of Drosophila cyclin E (DmcycE(JP)), which gives rise to adults with a rough eye phenotype. Amongst the dominant suppressors of DmcycE(JP), we identified brahma (brm) and moira (mor), which encode conserved core components of the Drosophila Brm complex that is highly related to the SWI-SNF ATP-dependent chromatin remodeling complex. Mutations in genes encoding other Brm complex components, including snr1 (BAP45), osa and deficiencies that remove BAP60 and BAP111 can also suppress the DmcycE(JP) eye phenotype. We show that Brm complex mutants suppress the DmcycE(JP) phenotype by increasing S phases without affecting DmcycE protein levels and that DmcycE physically interacts with Brm and Snr1 in vivo. These data suggest that the Brm complex inhibits S phase entry by acting downstream of DmcycE protein accumulation. The Brm complex also physically interacts weakly with Drosophila retinoblastoma (Rbf1), but no genetic interactions were detected, suggesting that the Brm complex and Rbf1 act largely independently to mediate G(1) arrest.
Insights
The Brahma (Brm) complex suppresses entry into S phase by acting downstream of Cyclin E accumulation. This chromatin remodeling complex interacts with Cyclin E, impacting cell cycle progression.
Area of Science:
- Cell cycle regulation
- Chromatin remodeling
- Molecular genetics
Background:
- Cyclin E-Cdk2 is crucial for initiating S phase.
- Understanding genes that interact with Cyclin E is key to deciphering cell cycle control.
- The Brahma (Brm) complex is a conserved chromatin remodeler related to SWI-SNF.
Purpose of the Study:
- To identify genes interacting with Drosophila Cyclin E (DmcycE).
- To investigate the role of the Brm complex in cell cycle regulation.
- To elucidate the relationship between DmcycE and the Brm complex in S phase entry.
Main Methods:
- Genetic screen using a hypomorphic mutation of Drosophila cyclin E (DmcycE(JP)) to identify dominant suppressors.
- Analysis of Brm complex components (brm, mor, snr1, osa) and their effect on the DmcycE(JP) eye phenotype.
- In vivo co-immunoprecipitation to assess physical interactions between DmcycE, Brm, Snr1, and Rbf1.
Main Results:
- Mutations in Brm complex genes (brm, mor, snr1, osa) suppress the DmcycE(JP) rough eye phenotype.
- Brm complex mutants increase S phase entry without altering DmcycE protein levels.
- DmcycE physically interacts with Brm and Snr1 in vivo; Brm complex interacts weakly with Rbf1.
Conclusions:
- The Brm complex inhibits S phase entry, acting downstream of DmcycE accumulation.
- The Brm complex plays a role in regulating cell cycle progression, independent of Rbf1's role in G1 arrest.
- This study reveals a novel interaction between chromatin remodeling and cell cycle control mediated by Cyclin E.