DF/HCC Program Affiliation

Co-Leader, Cancer Genetics Program
Member, Cancer Cell Biology Program

Research Abstract

We study the functions of the E2F transcription factor and retinoblastoma (RB) family of proteins, two groups of proteins that are important regulators of cell proliferation. During G1 to S phase progression, the activation of cyclin dependent kinases in G1 leads to the phosphorylation of RB-family proteins (pRB, p107 and p130), and the activation of the E2F-dependent transcription. E2F co-ordinates the expression of a set of genes that encode proteins that are essential for DNA synthesis. This series of events is tightly controlled in normal cells but is deregulated in most, if not all, tumor cells. Viral oncoproteins such as Adenovirus E1A, SV40 large T antigen and E7 proteins of human papillomaviruses have evolved to target RB-family proteins and the viruses exploit these interactions to drive quiescent cells into the cell cycle. We use a combination of genetic and biochemical approaches to study E2F and RB-family proteins. A major goal is to identify the individual functions of RB-family proteins in the regulation of E2F activity. Because the overexpression of closely related family members often leads to a loss of specificity, our recent efforts have concentrated on loss-of-function approaches. Using primary cells from knockout mice that lack various family members, we have identified E2F-target genes that require either pRB or p107/p130 for their normal patterns of expression and have begun to identify elements of cell cycle control that depend on either pRB, p107 or p130. To investigate the pathways that converge on E2F and the RB-family we have identified and characterized homologs of E2F (dE2F, dDP) and the RB-family (RBF) in Drosophila. We found that the Drosophila proteins control cell proliferation in ways that are directly analogous to their mammalian counterparts. We have two major goals that exploit the advantages of Drosophila. First, in order to identify the pathways that interact with E2F and RBF, we have set up genetic screens for mutations that modify dE2F/dDP- and RBF-dependent phenotypes. These phenotypes have been generated in transgenic lines by elevating the expression of dE2F, dDP and RBF specifically in the eye. Second, we are characterizing the phenotypes of mutant alleles of dE2F and RBF. Not surprisingly, these mutants have phenotypes that are far more severe than mutations of individual E2F or RB-family members in mice, and are likely to give insight into the general roles of these groups of proteins.

Publications

• Isaac CE, Francis SM, Martens AL, Julian LM, Seifried LA, Erdmann N, Binné UK, Harrington L, Sicinski P, Bérubé NG, Dyson NJ, Dick FA. The retinoblastoma protein regulates pericentric heterochromatin. Mol Cell Biol 2006 May; 26(9):3659-71
  PMID: 16612004
• Moon NS, Frolov MV, Kwon EJ, Di Stefano L, Dimova DK, Morris EJ, Taylor-Harding B, White K, Dyson NJ. Drosophila E2F1 has context-specific pro- and antiapoptotic properties during development. Dev Cell 2005 Oct; 9(4):463-75
  PMID: 16198289
• Frolov MV, Moon NS, Dyson NJ. dDP is needed for normal cell proliferation. Mol Cell Biol 2005 Apr; 25(8):3027-39
  PMID: 15798191
• Korenjak M, Taylor-Harding B, Binné UK, Satterlee JS, Stevaux O, Aasland R, White-Cooper H, Dyson N, Brehm A. Native E2F/RBF complexes contain Myb-interacting proteins and repress transcription of developmentally controlled E2F target genes. Cell 2004 Oct 15; 119(2):181-93
  PMID: 15479636
• Taylor-Harding B, Binné UK, Korenjak M, Brehm A, Dyson NJ. p55, the Drosophila ortholog of RbAp46/RbAp48, is required for the repression of dE2F2/RBF-regulated genes. Mol Cell Biol 2004 Oct; 24(20):9124-36
  PMID: 15456884
• Dick FA, Dyson N. pRB contains an E2F1-specific binding domain that allows E2F1-induced apoptosis to be regulated separately from other E2F activities. Mol Cell 2003 Sep; 12(3):639-49
  PMID: 14527410
• Dimova DK, Stevaux O, Frolov MV, Dyson NJ. Cell cycle-dependent and cell cycle-independent control of transcription by the Drosophila E2F/RB pathway. Genes Dev 2003 Sep 15; 17(18):2308-20
  PMID: 12975318
• Frolov MV, Huen DS, Stevaux O, Dimova D, Balczarek-Strang K, Elsdon M, Dyson NJ. Functional antagonism between E2F family members. Genes Dev 2001 Aug 15; 15(16):2146-60
  PMID: 11511545
• Dick FA, Sailhamer E, Dyson NJ. Mutagenesis of the pRB pocket reveals that cell cycle arrest functions are separable from binding to viral oncoproteins. Mol Cell Biol 2000 May; 20(10):3715-27
  PMID: 10779361
• Dyson N. The regulation of E2F by pRB-family proteins. Genes Dev 1998 Aug 1; 12(15):2245-62
  PMID: 9694791
• Hurford RK, Cobrinik D, Lee MH, Dyson N. pRB and p107/p130 are required for the regulated expression of different sets of E2F responsive genes. Genes Dev 1997 Jun 1; 11(11):1447-63
  PMID: 9192872