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Published on: May 1, 2020
RBF binding to both canonical E2F targets and noncanonical targets depends on functional dE2F/dDP complexes
Michael Korenjak1, Endre Anderssen, Sridhar Ramaswamy
1Massachusetts General Hospital Cancer Center and Harvard Medical School, Charlestown, Massachusetts, USA.
Molecular and Cellular Biology
|August 29, 2012
Summary
Retinoblastoma (RB) protein RBF1 requires E2F/DP complexes for all genomic targeting, even at sites lacking canonical E2F-binding motifs. This highlights the essential role of E2F/DP in regulating RB protein function.
Area of Science:
- Molecular Biology
- Genetics
- Epigenetics
Background:
- The retinoblastoma (RB) protein family regulates gene transcription by interacting with DNA-binding factors.
- While pRB's interaction with E2F transcription factors is well-known, RB proteins may target additional genomic sites via other chromatin-associated proteins.
- Understanding the extent of E2F-dependent and independent functions of RB proteins is crucial.
Purpose of the Study:
- To determine the genome-wide binding profiles of RBF1 and dE2F proteins in Drosophila.
- To investigate the scale of E2F-dependent versus E2F-independent functions of RBF1.
- To elucidate the role of E2F/DP complexes in the genomic targeting of RBF1.
Main Methods:
- Genome-wide binding profiles using chromatin immunoprecipitation-microarray (ChIP-chip) in Drosophila larvae.
- Quantitative PCR (qPCR) to validate binding sites.
- Cell fractionation to assess protein localization.
Main Results:
- RBF1 and dE2F2 proteins bind to numerous genes with diverse functions.
- dE2F1 binds to a smaller subset of promoters, potentially overriding RBF1/dE2F2 repression.
- Approximately 15% of RBF1-bound regions lack E2F-binding motifs.
- RBF1's stable association with chromatin is abolished in dDP mutants, irrespective of canonical E2F-binding sites.
Conclusions:
- E2F/DP complexes are essential for the genomic targeting of RBF1.
- All genomic targeting of RBF1, including at sites without canonical E2F motifs, requires E2F/DP complexes.
- This study reveals a fundamental dependency of RB protein chromatin association on E2F/DP heterodimers.
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