@article{liang_xiao_yin_hippenmeyer_horowitz_ghashghaei_2013, title={Neural development is dependent on the function of specificity protein 2 in cell cycle progression}, volume={140}, ISSN={["0950-1991"]}, DOI={10.1242/dev.085621}, abstractNote={Faithful progression through the cell cycle is crucial to the maintenance and developmental potential of stem cells. Here, we demonstrate that neural stem cells (NSCs) and intermediate neural progenitor cells (NPCs) employ a zinc-finger transcription factor specificity protein 2 (Sp2) as a cell cycle regulator in two temporally and spatially distinct progenitor domains. Differential conditional deletion of Sp2 in early embryonic cerebral cortical progenitors, and perinatal olfactory bulb progenitors disrupted transitions through G1, G2 and M phases, whereas DNA synthesis appeared intact. Cell-autonomous function of Sp2 was identified by deletion of Sp2 using mosaic analysis with double markers, which clearly established that conditional Sp2-null NSCs and NPCs are M phase arrested in vivo. Importantly, conditional deletion of Sp2 led to a decline in the generation of NPCs and neurons in the developing and postnatal brains. Our findings implicate Sp2-dependent mechanisms as novel regulators of cell cycle progression, the absence of which disrupts neurogenesis in the embryonic and postnatal brain.}, number={3}, journal={DEVELOPMENT}, author={Liang, Huixuan and Xiao, Guanxi and Yin, Haifeng and Hippenmeyer, Simon and Horowitz, Jonathan M. and Ghashghaei, H. Troy}, year={2013}, month={Feb}, pages={552–561} }
 @article{farina_cappabianca_ruggeri_di ianni_ragone_merolle_sano_stracke_horowitz_gulino_et al._2012, title={Constitutive autotaxin transcription by Nmyc-amplified and non-amplified neuroblastoma cells is regulated by a novel AP-1 and SP-mediated mechanism and abrogated by curcumin}, volume={586}, ISSN={["1873-3468"]}, DOI={10.1016/j.febslet.2012.08.026}, abstractNote={The motility, angiogenesis and metastasis‐stimulating factor Autotaxin (Atx), over expressed by human neuroblastomas (NB), is constitutively expressed by human Nmyc‐amplified SK‐N‐BE and non‐Nmyc‐amplified SH‐SY5Y NB cells. Here, we characterise a novel Atx transcriptional mechanism, utilised by both cell lines, that is restricted to the first 285 bp of the Atx promoter and involves AP‐1 and SP transcription factors, acting through a CRE/AP‐1‐like element at position −142 to −149 and a GAbox at position −227 to −235 relative to the Atx translational start site. This novel transcriptional mechanism can be inhibited by internally initiated SP‐3 and the natural phenol curcumin.}, number={20}, journal={FEBS LETTERS}, author={Farina, Antonietta R. and Cappabianca, Lucia and Ruggeri, Pierdomenico and Di Ianni, Natalia and Ragone, Marzia and Merolle, Stefania and Sano, Kimihiko and Stracke, Mary L. and Horowitz, Jonathan M. and Gulino, Alberto and et al.}, year={2012}, month={Oct}, pages={3681–3691} }
 @article{hawkridge_wysocky_petitte_anderson_mozdziak_fletcher_horowitz_muddiman_2010, title={Measuring the intra-individual variability of the plasma proteome in the chicken model of spontaneous ovarian adenocarcinoma}, volume={398}, ISSN={["1618-2650"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77957867631&partnerID=MN8TOARS}, DOI={10.1007/s00216-010-3979-y}, abstractNote={The domestic chicken (Gallus domesticus) has emerged as a powerful experimental model for studying the onset and progression of spontaneous epithelial ovarian cancer (EOC) with a disease prevalence that can exceed 35% between 2 and 7 years of age. An experimental strategy for biomarker discovery is reported herein that combines the chicken model of EOC, longitudinal plasma sample collection with matched tissues, advanced mass spectrometry-based proteomics, and concepts derived from the index of individuality (Harris, Clin Chem 20: 1535–1542, 1974). Blood was drawn from 148 age-matched chickens starting at 2.5 years of age every 3 months for 1 year. At the conclusion of the 1 year sample collection period, the 73 birds that remained alive were euthanized, necropsied, and tissues were collected. Pathological assessment of resected tissues from these 73 birds confirmed that five birds (6.8%) developed EOC. A proteomics workflow including in-gel digestion, nanoLC coupled to high-performance mass spectrometry, and label-free (spectral counting) quantification was used to measure the biological intra-individual variability (CVW) of the chicken plasma proteome. Longitudinal plasma sample sets from two birds within the 73-bird biorepository were selected for this study; one bird was considered “healthy” and the second bird developed late-stage EOC. A total of 116 proteins from un-depleted plasma were identified with 80 proteins shared among all sample sets. Analytical variability (CVA) of the label-free proteomics workflow was measured using a single plasma sample analyzed five times and was found to be ≥CVW in both birds for 16 proteins (20%) and in either bird for 25 proteins (31%). Ovomacroglobulin (ovostatin) was found to increase (p < 0.001) over a 6 month period in the late-stage EOC bird providing an initial candidate protein for further investigation.}, number={2}, journal={ANALYTICAL AND BIOANALYTICAL CHEMISTRY}, author={Hawkridge, Adam M. and Wysocky, Rebecca B. and Petitte, James N. and Anderson, Kenneth E. and Mozdziak, Paul E. and Fletcher, Oscar J. and Horowitz, Jonathan M. and Muddiman, David C.}, year={2010}, month={Sep}, pages={737–749} }
 @article{hawkridge_wysocky_petitte_anderson_mozdziak_fletcher_horowitz_muddiman_2010, title={Measuring the intra-individual variability of the plasma proteome in the chicken model of spontaneous ovarian adenocarcinoma (vol 398, pg 737, 2010)}, volume={398}, ISSN={["1618-2642"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77957848897&partnerID=MN8TOARS}, DOI={10.1007/s00216-010-4107-8}, number={4}, journal={ANALYTICAL AND BIOANALYTICAL CHEMISTRY}, author={Hawkridge, Adam M. and Wysocky, Rebecca B. and Petitte, James N. and Anderson, Kenneth E. and Mozdziak, Paul E. and Fletcher, Oscar J. and Horowitz, Jonathan M. and Muddiman, David C.}, year={2010}, month={Oct}, pages={1835–1835} }
 @article{kim_chiera_linder_trempus_smart_horowitz_2010, title={Overexpression of Transcription Factor Sp2 Inhibits Epidermal Differentiation and Increases Susceptibility to Wound- and Carcinogen-Induced Tumorigenesis}, volume={70}, ISSN={["1538-7445"]}, DOI={10.1158/0008-5472.can-10-1213}, abstractNote={Abstract}, number={21}, journal={CANCER RESEARCH}, author={Kim, Tae-Hyung and Chiera, Shannon L. and Linder, Keith E. and Trempus, Carol S. and Smart, Robert C. and Horowitz, Jonathan M.}, year={2010}, month={Nov}, pages={8507–8516} }
 @article{yin_nichols_horowitz_2010, title={Transcription of mouse Sp2 yields alternatively spliced and sub-genomic mRNAs in a tissue- and cell-type-specific fashion}, volume={1799}, DOI={10.1016/j.bbagrm.2010.03.002}, abstractNote={The Sp-family of transcription factors is comprised by nine members, Sp1-9, that share a highly conserved DNA-binding domain. Sp2 is a poorly characterized member of this transcription factor family that is widely expressed in murine and human cell lines yet exhibits little DNA-binding or trans-activation activity in these settings. As a prelude to the generation of a "knock-out" mouse strain, we isolated a mouse Sp2 cDNA and performed a detailed analysis of Sp2 transcription in embryonic and adult mouse tissues. We report that (1) the 5' untranslated region of Sp2 is subject to alternative splicing, (2) Sp2 transcription is regulated by at least two promoters that differ in their cell-type specificity, (3) one Sp2 promoter is highly active in nine mammalian cell lines and strains and is regulated by at least five discrete stimulatory and inhibitory elements, (4) a variety of sub-genomic messages are synthesized from the Sp2 locus in a tissue- and cell-type-specific fashion and these transcripts have the capacity to encode a novel partial-Sp2 protein, and (5) RNA in situ hybridization assays indicate that Sp2 is widely expressed during mouse embryogenesis, particularly in the embryonic brain, and robust Sp2 expression occurs in neurogenic regions of the post-natal and adult brain.}, number={7}, journal={Biochimica et Biophysica Acta. Gene Regulatory Mechanisms}, author={Yin, H. F. and Nichols, T. D. and Horowitz, J. M.}, year={2010}, pages={520–531} }
 @article{xie_yin_nichols_yoder_horowitz_2009, title={Sp2 Is a Maternally Inherited Transcription Factor Required for Embryonic Development}, volume={285}, ISSN={0021-9258 1083-351X}, url={http://dx.doi.org/10.1074/jbc.M109.078881}, DOI={10.1074/jbc.m109.078881}, abstractNote={The Sp family of transcription factors is required for the expression of cell cycle- and developmentally regulated genes, and the deregulated expression of a handful of family members is associated with human tumorigenesis. Sp2 is a relatively poorly characterized member of the Sp family that, although widely expressed, exhibits little or no DNA binding or transcriptional activity in human and mouse cell lines. To begin to address the role(s) played by Sp2 in early metazoan development we have cloned and characterized Sp2 from zebrafish (Danio rerio). We report that 1) the intron/exon organization and amino acid sequence of zebrafish Sp2 is closely conserved with its mammalian orthologues, 2) zebrafish Sp2 weakly stimulates an Sp-dependent promoter in vitro and associates with the nuclear matrix in a DNA-independent fashion, 3) zebrafish Sp2 is inherited as a maternal transcript, is transcribed in zebrafish embryos and adult tissues, and is required for completion of gastrulation, and 4) zebrafish lines carrying transgenes regulated by the Sp2 promoter recapitulate patterns of endogenous Sp2 expression.}, number={6}, journal={Journal of Biological Chemistry}, publisher={American Society for Biochemistry & Molecular Biology (ASBMB)}, author={Xie, Jianzhen and Yin, Haifeng and Nichols, Teresa D. and Yoder, Jeffrey A. and Horowitz, Jonathan M.}, year={2009}, month={Dec}, pages={4153–4164} }
 @article{rong_hu_huang_mackman_horowitz_jensen_durden_van meir_brat_2006, title={Early growth response gene-1 regulates hypoxia-induced expression of tissue factor in glioblastoma multiforme through hypoxia-inducible factor-1-independent mechanisms}, volume={66}, ISSN={["1538-7445"]}, DOI={10.1158/0008-5472.CAN-06-0346}, abstractNote={Abstract}, number={14}, journal={CANCER RESEARCH}, author={Rong, Yuan and Hu, Fang and Huang, RuoPan and Mackman, Nigel and Horowitz, Jonathan M. and Jensen, Randy L. and Durden, Donald L. and Van Meir, Erwin G. and Brat, Daniel J.}, year={2006}, month={Jul}, pages={7067–7074} }
 @article{simmons_horowitz_2006, title={Nkx3.1 binds and negatively regulates the transcriptional activity of Sp-family members in prostate-derived cells}, volume={393}, ISSN={["1470-8728"]}, DOI={10.1042/bj20051030}, abstractNote={Nkx3.1 is a homeodomain-containing transcription factor that is expressed early in the development of the prostate gland and is believed to play an important role in the differentiation of prostatic epithelia. Loss of Nkx3.1 protein expression is often an early event in prostate tumorigenesis, and the abundance of Nkx3.1-negative epithelial cells increases with disease progression. In a number of systems, homeodomain proteins collaborate with zinc-finger-containing transcription factors to bind and regulate target genes. In the present paper, we report that Nkx3.1 collaborates with Sp-family members in the regulation of PSA (prostate-specific antigen) in prostate-derived cells. Nkx3.1 forms protein complexes with Sp proteins that are dependent on their respective DNA-binding domains and an N-terminal segment of Nkx3.1, and Nkx3.1 negatively regulates Sp-mediated transcription via Trichostatin A-sensitive and -insensitive mechanisms. A distal 1000 bp portion of the PSA promoter is required for transrepression by Nkx3.1, although Nkx3.1 DNA-binding activity is itself not required. We conclude that Nkx3.1 negatively regulates Sp-mediated transcription via the tethering of histone deacetylases and/or by inhibiting the association of Sp proteins with co-activators.}, journal={BIOCHEMICAL JOURNAL}, author={Simmons, SO and Horowitz, JM}, year={2006}, month={Jan}, pages={397–409} }
 @article{moorefield_yin_nichols_cathcart_simmons_horowitz_2006, title={Sp2 localizes to subnuclear foci associated with the nuclear matrix}, volume={17}, ISSN={["1939-4586"]}, DOI={10.1091/mbc.E05-11-1063}, abstractNote={We have reported that extracts prepared from many human and mouse cell lines show little or no Sp2 DNA-binding activity and that Sp2 has little or no capacity to stimulate transcription of promoters that are activated by Sp1, Sp3, and Sp4. Using an array of chimeric Sp1/Sp2 proteins we showed further that Sp2 DNA-binding activity and trans-activation are each negatively regulated in mammalian cells. As part of an ongoing effort to study Sp2 function and regulation we characterized its subcellular localization in comparison with other Sp-family members in fixed and live cells. We report that 1) Sp2 localizes largely within subnuclear foci associated with the nuclear matrix, and 2) these foci are distinct from promyelocytic oncogenic domains and appear to be stable during an 18-h time course of observation. Deletion analyses identified a 37 amino acid sequence spanning the first zinc-“finger” that is sufficient to direct nuclear matrix association, and this region also encodes a bipartite nuclear localization sequence. A second nuclear matrix targeting sequence is encoded within the Sp2 trans-activation domain. We conclude that Sp2 preferentially associates with the nuclear matrix and speculate that this subcellular localization plays an important role in the regulation of Sp2 function.}, number={4}, journal={MOLECULAR BIOLOGY OF THE CELL}, author={Moorefield, KS and Yin, HF and Nichols, TD and Cathcart, C and Simmons, SO and Horowitz, JM}, year={2006}, month={Apr}, pages={1711–1722} }
 @article{spengler_kennett_moorefield_simmons_brattain_horowitz_2005, title={Sumoylation of internally initiated Sp3 isoforms regulates transcriptional repression via a Trichostatin A-insensitive mechanism}, volume={17}, ISSN={["1873-3913"]}, DOI={10.1016/j.cellsig.2004.06.007}, abstractNote={Sp3 is a ubiquitously expressed member of the Sp family of transcription factors that encodes three proteins, Sp3, M1 and M2, with differing capacities to stimulate or repress transcription. As part of ongoing efforts to study the functions of Sp3 isoforms, we employed a yeast “two-hybrid” screen to identify Sp3-binding proteins. This screen resulted in the identification of Ubc9, a SUMO-1 conjugating enzyme, as an M2-binding protein, and consistent with these results sequence analyses identified consensus sumoylation motifs within several Sp family members. Western blots probed with anti-Sp3 detected a high molecular weight Sp3 isoform that is stabilized by a SUMO-1 hydrolase inhibitor, and this protein is also bound by anti-SUMO-1 antiserum. Transient transfection assays with epitope-tagged-SUMO-1 and GFP-SUMO-1 fusion proteins confirmed that Sp3, M1 and M2 proteins are sumoylated in vivo. Substitution of arginine for lysine at one putative site of sumoylation, lysine551, blocked sumoylation of all Sp3 isoforms in vivo and led to a marginal increase in Sp3-mediated trans-activation in insect and mammalian cells. In contrast, introduction of this amino acid substitution within M1 converted it into a potent transcriptional trans-activator. We conclude that Sp3 isoforms are sumoylated in vivo and this post-translational modification plays an important role in the regulation of Sp3-mediated transcription.}, number={2}, journal={CELLULAR SIGNALLING}, author={Spengler, ML and Kennett, SB and Moorefield, KS and Simmons, SO and Brattain, MG and Horowitz, JM}, year={2005}, month={Feb}, pages={153–166} }
 @article{moorefield_fry_horowitz_2004, title={Sp2 DNA binding activity and trans-activation are negatively regulated in mammalian cells}, volume={279}, ISSN={["1083-351X"]}, DOI={10.1074/jbc.M313589200}, abstractNote={Previous studies have indicated that Sp2 binds poorly to GC-rich sequences bound by Sp1 and Sp3, and further functional analyses of Sp2 have been limited. To study Sp2-mediated transcription, we employed a PCR-based protocol to determine the Sp2 consensus DNA-binding sequence (5′-GGGCGGGAC-3′) and performed kinetic experiments to show that Sp2 binds this consensus sequence with high affinity (225 pm) in vitro. To determine the functional consequence of Sp2 interaction with this sequence in vivo, we transformed well characterized Sp-binding sites within the dihydrofolate reductase (DHFR) promoter to consensus Sp2-binding sites. Incorporation of Sp2-binding sites within the DHFR promoter increased Sp2-mediated trans-activation in transient co-transfection experiments but also revealed Sp2 to be a relatively weak trans-activator with little or no capacity for additive or synergistic trans-activation. Using chimeric molecules prepared with portions of Sp1 and Sp2 and the human prostate-specific antigen promoter, we show that Sp2 DNA binding activity and trans-activation are negatively regulated in mammalian cells. Taken together, our data indicate that Sp2 is functionally distinct relative to other Sp family members and suggest that Sp2 may play a unique role in cell physiology.}, number={14}, journal={JOURNAL OF BIOLOGICAL CHEMISTRY}, author={Moorefield, KS and Fry, SJ and Horowitz, JM}, year={2004}, month={Apr}, pages={13911–13924} }
 @article{kennett_moorefield_horowitz_2002, title={Sp3 represses gene expression via the titration of promoter-specific transcription factors}, volume={277}, ISSN={["0021-9258"]}, DOI={10.1074/jbc.M108661200}, abstractNote={We have determined previously that Sp3 encodes three distinct gene products as follows: a full-length protein (Sp3) that is an activator of transcription and two isoforms (M1 and M2) derived via internal translational initiation that function as transcriptional repressors. To identify amino acids and functions required for transcriptional repression, we employed PCR-directed mutagenesis to create a panel of mutated M2 proteins. Biochemical and functional analyses of these mutated proteins indicate that functions encoded by the M2 carboxyl terminus, such as DNA binding activity and the capacity to form multimeric complexes, are not required or sufficient for transcriptional repression. Instead, a 93-amino acid portion of the trans-activation domain was shown to be the minimal portion of M2 required to block Sp-dependent gene expression. Transcriptional analysis of three Sp-dependent promoters showed that mutations sustained by many M2 proteins result in promoter-specific effects. Regions of M2 required for physical interactions with five TATA box-associated factors (TAFIIs) were mapped, and mutations that disrupt the interaction of M2 with two of these proteins, TAFII70 and TAFII40, were identified. We conclude that Sp3- mediated transcriptional repression is due, at least in part, to competition for promoter-specific transcription factors.}, number={12}, journal={JOURNAL OF BIOLOGICAL CHEMISTRY}, author={Kennett, SB and Moorefield, KS and Horowitz, JM}, year={2002}, month={Mar}, pages={9780–9789} }
 @article{baek_horowitz_eling_2001, title={Molecular cloning and characterization of human nonsteroidal anti-inflammatory drug-activated gene promoter - Basal transcription is mediated by Sp1 and Sp3}, volume={276}, ISSN={["0021-9258"]}, DOI={10.1074/jbc.M101814200}, abstractNote={Nonsteroidal anti-inflammatory drug-activated gene (NAG-1) is known to be associated with anti-tumorigenic activity and belongs to the transforming growth factor-β superfamily. In the present study, we cloned the promoter region (−3500 to +41) and investigated the transcriptional regulatory mechanisms of the basal expression of the human NAG-1 gene. Several potential transcription factor-binding sites in this region were identified. Based on the results from clones of nested deletions, the construct between −133 and +41 base pairs contains three Sp1-binding sites (Sp1-A, Sp1-B, and Sp1-C), which confer basal transcription specific activity of NAG-1 expression. When the Sp1-C site was mutated (GG to TT), a 60–80% decrease in promoter activity was observed in HCT-116 cells. Gel shift, co-transfection, and chromatin immunoprecipitation assays showed that the Sp transcription factors bind to the Sp1-binding sites and transactivate NAG-1 expression. In addition, chicken ovalbumin upstream promoter-transcription factor 1 can interact with the C-terminal region of Sp1 and Sp3 proteins and induce NAG-1 promoter activity through Sp1 and Sp3 transcription factors. These results identify the critical regulatory regions for the human NAG-1 basal promoter. Furthermore, the results suggest that the level of expression of the NAG-1 gene will depend on the availability of Sp proteins and on co-factors such as chicken ovalbumin upstream promoter-transcription factor 1.}, number={36}, journal={JOURNAL OF BIOLOGICAL CHEMISTRY}, author={Baek, SJ and Horowitz, JM and Eling, TE}, year={2001}, month={Sep}, pages={33384–33392} }
 @article{lee_albanese_fu_m d'amico_lin_watanabe_haines_siegel_hung_yarden_et al._2000, title={Cyclin D1 is required for transformation by activated Neu and is induced through an E2F-dependent signaling pathway}, volume={20}, ISSN={["1098-5549"]}, DOI={10.1128/MCB.20.2.672-683.2000}, abstractNote={ABSTRACT The neu (c-erbB-2) proto-oncogene encodes a tyrosine kinase receptor that is overexpressed in 20 to 30% of human breast tumors. Herein, cyclin D1 protein levels were increased in mammary tumors induced by overexpression of wild-type Neu or activating mutants of Neu in transgenic mice and in MCF7 cells overexpressing transforming Neu. Analyses of 12 Neu mutants in MCF7 cells indicated important roles for specific C-terminal autophosphorylation sites and the extracellular domain in cyclin D1 promoter activation. Induction of cyclin D1 by NeuT involved Ras, Rac, Rho, extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38, but not phosphatidylinositol 3-kinase. NeuT induction of the cyclin D1 promoter required the E2F and Sp1 DNA binding sites and was inhibited by dominant negative E2F-1 or DP-1. Neu-induced transformation was inhibited by a cyclin D1 antisense or dominant negative E2F-1 construct in Rat-1 cells. Growth of NeuT-transformed mammary adenocarcinoma cells in nude mice was blocked by the cyclin D1 antisense construct. These results demonstrate that E2F-1 mediates a Neu-signaling cascade tocyclin D1 and identify cyclin D1 as a critical downstream target of neu-induced transformation.}, number={2}, journal={MOLECULAR AND CELLULAR BIOLOGY}, author={Lee, RJ and Albanese, C and Fu, MF and M D'Amico and Lin, B and Watanabe, G and Haines, GK and Siegel, PM and Hung, MC and Yarden, Y and et al.}, year={2000}, month={Jan}, pages={672–683} }
 @article{sterner_dew-knight_musahl_kornbluth_horowitz_1998, title={Negative regulation of DNA replication by the retinoblastoma protein is mediated by its association with MCM7}, volume={18}, ISSN={["0270-7306"]}, DOI={10.1128/MCB.18.5.2748}, abstractNote={ABSTRACT A yeast two-hybrid screen was employed to identify human proteins that specifically bind the amino-terminal 400 amino acids of the retinoblastoma (Rb) protein. Two independent cDNAs resulting from this screen were found to encode the carboxy-terminal 137 amino acids of MCM7, a member of a family of proteins that comprise replication licensing factor. Full-length Rb and MCM7 form protein complexes in vitro, and the amino termini of two Rb-related proteins, p107 and p130, also bind MCM7. Protein complexes between Rb and MCM7 were also detected in anti-Rb immunoprecipitates prepared from human cells. The amino-termini of Rb and p130 strongly inhibited DNA replication in an MCM7-dependent fashion in a Xenopus in vitro DNA replication assay system. These data provide the first evidence that Rb and Rb-related proteins can directly regulate DNA replication and that components of licensing factor are targets of the products of tumor suppressor genes.}, number={5}, journal={MOLECULAR AND CELLULAR BIOLOGY}, author={Sterner, JM and Dew-Knight, S and Musahl, C and Kornbluth, S and Horowitz, JM}, year={1998}, month={May}, pages={2748–2757} }
 @article{tao_kassatly_cress_horowitz_1997, title={Subunit composition determines E2F DNA-binding site specificity}, volume={17}, ISSN={["1098-5549"]}, DOI={10.1128/MCB.17.12.6994}, abstractNote={The product of the retinoblastoma (Rb) susceptibility gene, Rb-1, regulates the activity of a wide variety of transcription factors, such as E2F, in a cell cycle-dependent fashion. E2F is a heterodimeric transcription factor composed of two subunits each encoded by one of two related gene families, denoted E2F and DP. Five E2F genes, E2F-1 through E2F-5, and two DP genes, DP-1 and DP-2, have been isolated from mammals, and heterodimeric complexes of these proteins are expressed in most, if not all, vertebrate cells. It is not yet clear whether E2F/DP complexes regulate overlapping and/or specific cellular genes. Moreover, little is known about whether Rb regulates all or a subset of E2F-dependent genes. Using recombinant E2F, DP, and Rb proteins prepared in baculovirus-infected cells and a repetitive immunoprecipitation-PCR procedure (CASTing), we have identified consensus DNA-binding sites for E2F-1/DP-1, E2F-1/DP-2, E2F-4/DP-1, and E2F-4/DP-2 complexes as well as an Rb/E2F-1/DP-1 trimeric complex. Our data indicate that (i) E2F, DP, and Rb proteins each influence the selection of E2F-binding sites; (ii) E2F sites differ with respect to their intrinsic DNA-bending properties; (iii) E2F/DP complexes induce distinct degrees of DNA bending; and (iv) complex-specific E2F sites selected in vitro function distinctly as regulators of cell cycle-dependent transcription in vivo. These data indicate that the specific sequence of an E2F site may determine its role in transcriptional regulation and suggest that Rb/E2F complexes may regulate subsets of E2F-dependent cellular genes.}, number={12}, journal={MOLECULAR AND CELLULAR BIOLOGY}, author={Tao, YX and Kassatly, RF and Cress, WD and Horowitz, JM}, year={1997}, month={Dec}, pages={6994–7007} }