scholarly journals The E2A-HLF Oncoprotein ActivatesGroucho-Related Genes and SuppressesRunx1

2001 ◽  
Vol 21 (17) ◽  
pp. 5935-5945 ◽  
Author(s):  
Jinjun Dang ◽  
Takeshi Inukai ◽  
Hidemitsu Kurosawa ◽  
Kumiko Goi ◽  
Toshiya Inaba ◽  
...  
Keyword(s):  
Dna Binding ◽  
B Cell ◽  
Fusion Gene ◽  
Chromosomal Translocation ◽  
Immunoblot Analysis ◽  
Binding Activity ◽  
Representational Difference Analysis ◽  
Transactivation Domain ◽  
Dimerization Domain ◽  
Dna Binding Activity

ABSTRACT The E2A-HLF fusion gene, formed by the t(17;19)(q22;p13) chromosomal translocation in leukemic pro-B cells, encodes a chimeric transcription factor consisting of the transactivation domain of E2A linked to the bZIP DNA-binding and protein dimerization domain of hepatic leukemia factor (HLF). This oncoprotein blocks apoptosis induced by growth factor deprivation or irradiation, but the mechanism for this effect remains unclear. We therefore performed representational difference analysis (RDA) to identify downstream genetic targets of E2A-HLF, using a murine FL5.12 pro-B cell line that had been stably transfected with E2A-HLF cDNA under the control of a zinc-regulated metallothionein promoter. Two RDA clones, designated RDA1 and RDA3, were differentially upregulated in E2A-HLF-positive cells after zinc induction. The corresponding cDNAs encoded two WD40 repeat-containing proteins, Grg2 and Grg6. Both are related to the Drosophila protein Groucho, a transcriptional corepressor that lacks DNA-binding activity on its own but can act in concert with other proteins to regulate embryologic development of the fly. Expression of both Grg2 and Grg6 was upregulated 10- to 50-fold by E2A-HLF. Immunoblot analysis detected increased amounts of two additional Groucho-related proteins, Grg1 and Grg4, in cells expressing E2A-HLF. A mutant E2A-HLF protein with a disabled DNA-binding region also mediated pro-B cell survival and activated Groucho-related genes. Among the transcription factors known to interact with Groucho-related protein, only RUNX1 was appreciably downregulated by E2A-HLF. Our results identify a highly conserved family of transcriptional corepressors that are activated by E2A-HLF, and they suggest that downregulation of RUNX1 may contribute to E2A-HLF-mediated leukemogenesis.

scholarly journals Structure of the p53/RNA polymerase II assembly

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Shu-Hao Liou ◽  
Sameer K. Singh ◽  
Robert H. Singer ◽  
Robert A. Coleman ◽  
Wei-Li Liu
Keyword(s):  
Dna Binding ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Conformational Changes ◽  
P53 Protein ◽  
Binding Activity ◽  
Transactivation Domain ◽  
Pol Ii ◽  
Dna Binding Activity ◽  
Regulated Gene Expression

AbstractThe tumor suppressor p53 protein activates expression of a vast gene network in response to stress stimuli for cellular integrity. The molecular mechanism underlying how p53 targets RNA polymerase II (Pol II) to regulate transcription remains unclear. To elucidate the p53/Pol II interaction, we have determined a 4.6 Å resolution structure of the human p53/Pol II assembly via single particle cryo-electron microscopy. Our structure reveals that p53’s DNA binding domain targets the upstream DNA binding site within Pol II. This association introduces conformational changes of the Pol II clamp into a further-closed state. A cavity was identified between p53 and Pol II that could possibly host DNA. The transactivation domain of p53 binds the surface of Pol II’s jaw that contacts downstream DNA. These findings suggest that p53’s functional domains directly regulate DNA binding activity of Pol II to mediate transcription, thereby providing insights into p53-regulated gene expression.

Transformation by Fos proteins requires a C-terminal transactivation domain

1993 ◽  
Vol 13 (12) ◽  
pp. 7429-7438
Author(s):  
R Wisdon ◽  
I M Verma
Keyword(s):  
Dna Binding ◽  
Leucine Zipper ◽  
Fibroblast Cell ◽  
Binding Activity ◽  
Sequence Specificity ◽  
Transactivation Domain ◽  
Functional Requirements ◽  
Dna Binding Activity ◽  
The Difference ◽  
Transforming Proteins

The Fos family of proteins now includes seven members: the retroviral proteins FBR-v-Fos and FBJ-v-Fos and the cellular proteins c-Fos, FosB, FosB2, Fra1, and Fra2. Four proteins (FBR-v-Fos, FBJ-v-Fos, c-Fos, and FosB) transform established rodent fibroblast cell lines, while three (FosB2, Fra1, and Fra2) do not. As all family members display sequence-specific DNA-binding activity as part of a heterodimeric complex with Jun proteins, other features must account for the differences in transforming potential. We demonstrate here that all transforming members have a C-terminal transactivation domain that is lacking in nontransforming members. The nontransforming proteins Fra1 and Fra2 can be converted to transforming proteins by fusion of a transactivation domain from either FosB or VP16. We also demonstrate that differences in the basic region-leucine zipper domain affecting either the affinity or sequence specificity of DNA binding are not determinants of the difference in transforming potential among members of the Fos family. The results further define the functional requirements for transformation by Fos proteins and suggest that the subunit composition of AP1 complexes is an important determinant of mitogenic signalling capability.

Identification of Cyclin D3 as a Direct Transcriptional Target of E2A Using Damid.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1618-1618
Author(s):  
John K. Choi ◽  
Siyuan Song ◽  
Jonathan Cooperman ◽  
Danielle L. Letting ◽  
Gerd A. Blobel
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
B Cell ◽  
Target Genes ◽  
Cell Development ◽  
Binding Activity ◽  
B Cell Development ◽  
Cyclin D3 ◽  
Dna Binding Activity ◽  
E Boxes

Abstract The transcription factor E2A is required for very early B cell development. The exact mechanism by which E2A promotes B cell development is unclear and cannot be explained by the known E2A targets, components of the pre-B cell receptor and cyclin dependent kinase inhibitors, indicating additional pathways and targets remain to be identified. We had previously reported that E2A can promote precursor B cell expansion, promote G1 cell cycle progression, and induce the expressions of multiple G1 phase cyclins including cyclin D3, suggesting that E2A induction of these genes may contribute to early B cell development. To better understand the mechanism by which E2A induces these cyclins, we characterized the relationship between E2A and the cyclin D3 gene promoter. E2A transactivated a luciferase reporter plasmid containing the 1kb promoter of cyclin D3 that contains two consensus E2A binding sites (E-boxes); however, deletion of the E-boxes did not disrupt the transactivation by E2A. We hypothesized three possible mechanisms: 1) indirect activation of cyclin D3 via another transcription factor, 2) binding of E2A to cryptic non-E-boxes, or 3) recruitment of E2A to the promoter via interaction with other DNA binding factor. To test the first possibility, promoter occupancy was examined using the DamID approach. In this approach, a fusion protein consisting of E. coli DNA adenosine methyltransferase (DAM) and a transcription factor of interest is expressed at low levels, resulting in specific methylation of adenosine residues within 2–5 kb of the transcription factor target sites. A fusion construct composed of E2A and DAM (E47Dam), was subcloned in lentiviral vectors, and used to transduce precursor B cell lines. The methylated adenosine residues were detected using a sensitive ligation-mediated PCR (LM-PCR) assay that required only 1 ug of genomic DNA and can detect methylation even if only 3% of the cells express E47Dam; no methylated adenosines were detected in control cells, indicating that all methylated residues resulted from E47Dam. Specific adenosine methylation was identified at the IgH intronic enhancer, a known E2A target site, but not at the non-target sites, CD19, HPRT, and GAPDH promoters. Specific methylation was detected at the cyclin D3 promoter but not 10 kb down-stream, despite similar concentrations of E-boxes at both sites. Chromatin immunoprecipitation analysis confirmed the DamID findings and further localized the binding to within 1 kb of the two E-boxes in the cyclin D3 promoter. To distinguish between the two remaining mechanisms (cryptic non-E-boxes versus recruitment via other DNA binding factors), two point mutations were introduced into E47Dam that disrupted its DNA binding activity. The mutated E47Dam continued to methylate at the cyclin D3 promoter. We conclude that E2A can be recruited to the cyclin D3 promoter, independent of E-boxes or E2A DNA binding activity. Our findings raise the possibility that some direct E2A target genes may lack functional E-boxes. Furthermore, mutated E2A, lacking an E2A DNA binding domain, that is seen in 6% of pediatric ALLs may still activate a subset of E2A target genes. Finally, our application of lentiviral vectors and LM-PCR to the DamID approach should permit analysis of primary human precursor B cells, despite the limitations in cell number and transduction efficiency.

Analysis Of E2A Point Mutations In B Cell Leukemia

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4850-4850
Author(s):  
Eroica Soans ◽  
John K Choi
Keyword(s):  
Dna Binding ◽  
B Cell ◽  
Binding Activity ◽  
Luciferase Reporter ◽  
Reporter Assay ◽  
Cell Leukemia ◽  
Wild Type ◽  
Dna Binding Activity ◽  
E Box ◽  
B Cell Leukemia

Abstract Introduction TCF3 encodes for E2A protein, which belongs to the helix loop helix transcription factor family. E2A activates transcription of downstream genes by binding to E-box motifs as a homo or hetero dimer. E2A plays an important role in B lymphocyte development. Therefore deletion or mutations in TCF3 or even lowered activity of E2A are causes of B cell leukemia and lymphomas. Recently, three mutations V557E, D561E and N551K in E2A were isolated in Burkitt’s lymphoma (Schmitz, Young et al. 2012). The first two mutations are present in the homo dimerization region of E2A while N551K is present in the DNA binding region. Though the paper enumerated role of TCF3 in Burkitt’s lymphoma but the significance of these TCF3 mutations or mechanism needed further characterization. We hypothesized that these TCF3 mutations have an alternate mechanism as compared to wild type TCF3 and therefore may affect B cell development. Methods We characterized three TCF3 mutants by cloning them into in MIGR1 backbone using TOPO cloning. E2A activity was measured using an E2A-specific luciferase reporter assay in 293T cells. DNA binding activity was measured using a DNA protein binding colorimetric assay. Results V557E and D561E mutants have lower activity as compared to wild type E2A as studied using E2A-specific luciferase reporter assay; while N551K showed no activity in the same assay as compared to wild type E2A activity. Similarly V557E and D561 form weaker bonds with the E box motifs while N551K showed no DNA binding activity as studied using colorimetric DNA-protein binding assay. The plasmid expressions were verified using western blot analysis. Conclusion Our findings suggest mutations V557E and D561E may follow a similar pathway as wild-type E2A but have lower activity. The N551K mutation has an alternate pathway to wild type TCF3 that may impact B cell proliferation, survival and development. Disclosures: No relevant conflicts of interest to declare.

NFκB Signaling and Mcl-1 Are Critical in B Cell Maturation Antigen-Promoted Multiple Myeloma Cell Growth and Survival

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3384-3384
Author(s):  
Chirag Acharya ◽  
Gang An ◽  
Mike Y Zhong ◽  
Michele Cea ◽  
Antonia Cagnetta ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Dna Binding ◽  
B Cell ◽  
Binding Activity ◽  
Cell Maturation ◽  
Dependent Manner ◽  
Dna Binding Activity ◽  
B Cell Maturation ◽  
Mouse Xenograft Model ◽  
B Cell Maturation Antigen

Abstract B cell maturation antigen (BCMA), selectively elevated in malignant plasma cells, is an ideal target antigen for immunotherapies for multiple myeloma (MM). Most recently, we reported novel antagonistic anti-BCMA antibody drug conjugates (ADCs) showing potent and specific anti-MM activities via effector cell-dependent and -independent mechanisms in vitro and in vivo (Blood 2014; 123:3128) We here further characterize molecular mechanisms of BCMA activation in MM cells in the bone marrow microenvironment by directly manipulating BCMA receptor levels in MM cells and ligation of a proliferation-inducing ligand (APRIL) to MM cells. Three MM cell lines H929, MM1S, and RPMI8226 with highest, medium, and low BCMA, respectively, were either transfected with lentiviruses of BCMA shRNA or cDNA. First, downregulation of BCMA significantly blocked viability of all 3 MM cells and induced caspase3/7 activities, which led to potent reduction of colony formation in a 3-week methylcellulose culture. Next, MM1R and H929 transfectants with the Doxycyclin (dox)-inducible lentiviral expression vector pTRIPZ shBCMA were generated. Time-dependent BCMA reduction only occurred in dox (1 ug/ml)-containing media. Dox-dependent BCMA inhibition was followed by decreased anti-apoptotic genes (Mcl1, Bcl-2, XIAP, NAIP, NFκB1, NFκB2) and proliferative genes (CCND2, CDK4/6, c-MYC). Conversely, overexpression of BCMA in RPMI8226 by either pCMV6/BCMA vector or pLocBCMA lentiviruses significantly increased NFκB (p65, p50, p52) DNA binding activity. Anti-apoptotic gene and cell proliferation genes were also up-regulated in BCMA-overexpressing MM cells. In addition, osteoclast activation factors MIP-1α/β, SDF-1, angiogenesis factors (VEGF, PECAM-1), adhesion proteins (CD44, ICAM1), as well as immunosuppressive factor TGFβ were augmented in BCMA-overexpressing MM cells. Importantly, opposite effects on these downstream genes were seen in BCMA-knockdown MM cells. Moreover, stimulation of 3 MM cells by APRIL robustly induces NFκB DNA binding activity (p65, p50, and p52, to a lesser extend) and activates PI3K/AKT and ERK1/2 signaling. APRIL also induces pro-survival/anti-apoptotic targets (BCL2A1, NFκB1, NFκB2) and chemotactic/osteoclast activating factors (MIP1α and MIP1β) in a dose-dependent manner. Angiogenesis and adhesion/chemoattractant factors (VEGF, IL-8, CXCL10, and RANTES) were also significantly induced upon APRIL stimulation. In contrast, BCMA-Fc protein that blocks APRIL binding to BCMA, inhibits secretion of these cytokines/chemokines, indicating specific response of engagement of BCMA by APRIL in BCMA-expressing MM cells. APRIL induced adhesion and migration of MM cells whereas BCMA-Fc blocked APRIL-induced responses. Finally, RPMI8226/pLocBCMA cells induce earlier tumor onset and more tumor growth in mouse xenograft model when compared with control RPMI8226 cells. In contrast, pTRIPZ shBCMA H929 cells induce significantly less tumor formation and further prolong survival of mice fed with dox(2 ug/ml)-containing water than those without dox. Together, these results define molecular regulators of active APRIL/BCMA signaling cascade in the MM BM milieu, further supporting targeting APRIL/BCMA in MM. Disclosures Anderson: Celgene: Consultancy; Sanofi-Aventis: Consultancy; Onyx: Consultancy; Acetylon: Scientific Founder, Scientific Founder Other; Oncoprep: Scientific Founder Other; Gilead Sciences: Consultancy.

Mutations in the B-Cell Transcription Factor PAX5 Found in B-Progenitor Acute Lymphoblastic Leukemia Impair Normal PAX5 Activity.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 613-613 ◽  
Author(s):  
Christopher B. Miller ◽  
Charles G. Mullighan ◽  
James R. Downing
Keyword(s):  
Dna Binding ◽  
B Cell ◽  
Transcriptional Activation ◽  
Fusion Proteins ◽  
Transcriptional Activity ◽  
Binding Activity ◽  
B Cell Development ◽  
Wild Type ◽  
Paired Domain ◽  
Dna Binding Activity

Abstract Using genome-wide profiling of DNA copy number abnormalities using high-resolution single nucleotide polymorphism arrays, we recently identified a high frequency of genomic aberrations involving the PAX5 gene in pediatric B-progenitor ALL. PAX5 is a critical transcriptional regulator of B lymphocyte commitment and differentiation. Mutations, including partial tandem duplication, complete and focal deletions, point mutations in the DNA-binding or transactivation domain, and three translocations that encode PAX5 fusion proteins were observed in 31.7% of B-ALL. The PAX5 deletions were mono-allelic and resulted in either loss of the entire gene, or the deletion of only a subset of the exons leading to the production of PAX5 proteins that lacked the DNA-binding paired domain (exons 2–4) and/or the transcriptional activation domain (exons 7–10). In murine systems, the complete absence of PAX5 results in the arrest of B-cell development at the pro-B-cell stage prior to immunoglobulin heavy chain rearrangement, whereas haploinsufficiency leads to a partial block in B-cell development. Importantly, in the primary leukemia samples, the mono-allelic loss of PAX5 was associated with reduced expression of PAX5 by flow cytometry and quantitative RT-PCR, suggesting that haploinsufficiency contributes to the block in differentiation characteristic of B-progenitor ALL. To determine if the other identified PAX5 mutations result in hypomorphic alleles, we analyzed the DNA-binding and transcriptional activity of the encoded proteins. DNA-binding activity was assessed by electrophoretic mobility gel-shift assays using a labeled oligonucleotide probes from the promoters of the PAX5 target genes CD19 and CD79A (mb-1), and transcriptional activity was assessed by a luciferase-based reporter assays using the PAX5-dependent reporter plasmid, luc-CD19. Analysis was performed on the paired-domain mutants P80R and P34Q, the focal deletions Δe2-5, Δe2-6, Δe2-7, Δe2-8, and Δe6-8, and the PAX5-ETV6 and PAX5-FOXP1 translocation-encoded fusion proteins. As expected, DNA-binding was abrogated in deletion mutants that lacked the paired domain (Δe2-5, Δe2-6, Δe2-7, Δe2-8). In contrast, the PAX5 Δe6-8, which retains the paired DNA binding domain but lacks a significant portion of the transcriptional regulatory domain, had normal DNA binding activity. Importantly, the paired domain point mutants impaired DNA-binding in a promoter specific manner, with P80R having a marked reduction in binding to both the CD19 and mb-1 promoters, whereas P34Q showed reduced binding only to the mb-1 promoter. Surprisingly, the PAX5-ETV6 and the PAX5-FOXP1 translocations had markedly reduced DNA-binding activity despite retention of the PAX5 paired domain. As expected each of the mutants with impaired or absent DNA-binding activity were found to have markedly reduced transcriptional activity when compared to wild type PAX5. Similarly, those mutants with altered or deleted transcriptional activation domains had reduced transcriptional activity, as did the two PAX5 translocation-encoded fusion proteins (PAX5-ETV6 and PAX5-FOXP1). Moreover, transfection of increasing amounts of PAX5-ETV6 or PAX5-FOXP1 together with a fixed amount of wild type PAX5 revealed that the fusion proteins competitively inhibit the transcriptional activation of wild type PAX5. Taken together, these data indicate that the identified PAX5 mutations impair DNA-binding and/or transcriptional activity. This loss of normal PAX5 function in turn would contribute to the observed arrest in B-cell development seen in ALL.

The MMSET Protein Is Tightly Associated with Chromatin, Mediates Methylation of Specific Histone Residues and Forms a Complex with a Histone Demethylase.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 730-730
Author(s):  
Jotin Marango ◽  
Boris A. Leibovitch ◽  
Manabu Shimoyama ◽  
Hitomi Nishio ◽  
Samuel Waxman ◽  
...  
Keyword(s):  
Dna Binding ◽  
B Cell ◽  
Cell Line ◽  
Dna Sequences ◽  
Cpg Island ◽  
Regulatory Elements ◽  
Binding Activity ◽  
Chain Gene ◽  
Pwwp Domain ◽  
Dna Binding Activity

Abstract Over 40% of cases of multiple myeloma (MM) are associated with translocations of the immunoglobulin heavy (IgH) chain gene. The t(4;14) translocation, present in ca. 15% of myeloma cases, results in the overexpression of two potential oncogenes, MMSET and FGFR3, via juxtaposition of their endogenous promoters to regulatory elements of the IgH locus. The presence of t(4;14) and MMSET overexpression are adverse prognostic factors in MM irrespective of FGFR3 expression, implicating MMSET in disease pathogenesis. We previously reported the presence of repression domains and the ability of MMSET to methylate histones. Examination of a number of MMSET isoforms generated by different chromosomal breakpoints in the t(4;14) translocation indicated that a N-terminal portion of the protein containing a PWWP domain mediated tight association of MMSET with chromatin. To determine if this region of the protein could mediate DNA binding we incubated bacterially expressed MMSET with DNA cellulose. Both the N-terminal and C-terminal portions of the protein showed DNA binding activity with different affinities. To isolate DNA sequences potentially bound by MMSET we incubated immunoprecipitated MMSET with a library of human CpG island DNA fragments, selected the bound DNA and performed several rounds of re-amplification and binding of selected sequences. A small family of clones was obtained, having several sequence motifs in common, suggesting specific DNA binding activity by the MMSET complex. The C-terminal region of MMSET containing a SET domain and a PHD finger, in addition to binding naked DNA, bound to native histones H3 and H4. These data suggest that MMSET may specifically target particular genes through recognition of DNA sequences and histones, or possibly specific histone modifications. Subsequently, MMSET may regulate these genes by further modifying the adjacent chromatin. In vitro analysis showed that recombinant MMSET could methylate several lysine residues on core histones, including H3K4, H3K36 and H4K20. However, MMSET immunopurified from a t(4;14)-positive myeloma cell line was only able to methylate histone H4. Additionally, a B-cell line engineered to overexpress MMSET in a conditional manner showed a global increase in the level of tri-methylated H4K20 and modulation of specific sets of genes involved in apoptosis. To determine if MMSET could indeed affect the chromatin configuration of a model gene, MMSET was fused to the Gal4 DNA binding domain and expressed in cells harboring a chromatin-embedded Gal4 reporter. MMSET repressed this reporter and chromatin immunoprecipitation demonstrated that this was accompanied by an increase in H4K20 tri-methylation. Finally, we found that endogenous MMSET could complex with Lysine-Specific Demethylase 1 (LSD1). Accordingly, the targeting of MMSET to the Gal4 reporter gene also led to a loss of H3K4 methylation, consistent with transcriptional repression. Collectively these data indicate that MMSET is a transcriptional effector that can target specific segments of chromatin and mediate a series of repressive changes. Misexpression of MMSET may lead to significant genetic re-programming of the B cell and contribute to myeloma development.

scholarly journals Transformation by Fos proteins requires a C-terminal transactivation domain.

1993 ◽  
Vol 13 (12) ◽  
pp. 7429-7438 ◽  
Author(s):  
R Wisdon ◽  
I M Verma
Keyword(s):  
Dna Binding ◽  
Leucine Zipper ◽  
Fibroblast Cell ◽  
Binding Activity ◽  
Sequence Specificity ◽  
Transactivation Domain ◽  
Functional Requirements ◽  
Dna Binding Activity ◽  
The Difference ◽  
Transforming Proteins

The Fos family of proteins now includes seven members: the retroviral proteins FBR-v-Fos and FBJ-v-Fos and the cellular proteins c-Fos, FosB, FosB2, Fra1, and Fra2. Four proteins (FBR-v-Fos, FBJ-v-Fos, c-Fos, and FosB) transform established rodent fibroblast cell lines, while three (FosB2, Fra1, and Fra2) do not. As all family members display sequence-specific DNA-binding activity as part of a heterodimeric complex with Jun proteins, other features must account for the differences in transforming potential. We demonstrate here that all transforming members have a C-terminal transactivation domain that is lacking in nontransforming members. The nontransforming proteins Fra1 and Fra2 can be converted to transforming proteins by fusion of a transactivation domain from either FosB or VP16. We also demonstrate that differences in the basic region-leucine zipper domain affecting either the affinity or sequence specificity of DNA binding are not determinants of the difference in transforming potential among members of the Fos family. The results further define the functional requirements for transformation by Fos proteins and suggest that the subunit composition of AP1 complexes is an important determinant of mitogenic signalling capability.

scholarly journals E2F-5, a new E2F family member that interacts with p130 in vivo.

1995 ◽  
Vol 15 (6) ◽  
pp. 3082-3089 ◽  
Author(s):  
E M Hijmans ◽  
P M Voorhoeve ◽  
R L Beijersbergen ◽  
L J van 't Veer ◽  
R Bernards
Keyword(s):  
Cell Cycle ◽  
Dna Binding ◽  
Gene Family ◽  
Binding Activity ◽  
Transactivation Domain ◽  
Retinoblastoma Gene ◽  
Dna Binding Activity ◽  
E2f Transcription Factors ◽  
G0 Phase

E2F DNA binding sites are found in a number of genes whose expression is tightly regulated during the cell cycle. The activity of E2F transcription factors is regulated by association with specific repressor molecules that can bind and inhibit the E2F transactivation domain. For E2F-1, E2F-2, and E2F-3, the repressor is the product of the retinoblastoma gene, pRb. E2f-4 interacts with pRb-related p107 and not with pRb itself. Recently, a cDNA encoding a third member of the retinoblastoma gene family, p130, was isolated. p130 also interacts with E2F DNA binding activity, primarily in the G0 phase of the cell cycle. We report here the cloning of a fifth member of the E2F gene family. The human E2F-5 cDNA encodes a 346-amino-acid protein with a predicted molecular mass of 38 kDa. E2F-5 is more closely related to E2F-4 (78% similarity) than to E2F-1 (57% similarity). E2F-5 resembles the other E2Fs in that it binds to a consensus E2F site in a cooperative fashion with DP-1. By using a specific E2F-5 antiserum, we found that under physiological conditions, E2F-5 interacts preferentially with p130.

scholarly journals Clp-dependent proteolysis of the LexA N-terminal domain in Staphylococcus aureus

Microbiology ◽  
2011 ◽  
Vol 157 (3) ◽  
pp. 677-684 ◽  
Author(s):  
Marianne T. Cohn ◽  
Peter Kjelgaard ◽  
Dorte Frees ◽  
José R. Penadés ◽  
Hanne Ingmer
Keyword(s):  
Staphylococcus Aureus ◽  
Dna Binding ◽  
Bacterial Species ◽  
Transcriptional Regulator ◽  
Sos Response ◽  
Binding Activity ◽  
Dimerization Domain ◽  
Dna Binding Activity ◽  
Lexa Repressor ◽  
Induced Mutagenesis

The SOS response is governed by the transcriptional regulator LexA and is elicited in many bacterial species in response to DNA damaging conditions. Induction of the SOS response is mediated by autocleavage of the LexA repressor resulting in a C-terminal dimerization domain (CTD) and an N-terminal DNA-binding domain (NTD) known to retain some DNA-binding activity. The proteases responsible for degrading the LexA domains have been identified in Escherichia coli as ClpXP and Lon. Here, we show that in the human and animal pathogen Staphylococcus aureus, the ClpXP and ClpCP proteases contribute to degradation of the NTD and to a lesser degree the CTD. In the absence of the proteolytic subunit, ClpP, or one or both of the Clp ATPases, ClpX and ClpC, the LexA domains were stabilized after autocleavage. Production of a stabilized variant of the NTD interfered with mitomycin-mediated induction of sosA expression while leaving lexA unaffected, and also significantly reduced SOS-induced mutagenesis. Our results show that sequential proteolysis of LexA is conserved in S. aureus and that the NTD may differentially regulate a subset of genes in the SOS regulon.

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