The human ZBP-89 homolog, located at chromosome 3q21, represses gastrin gene expression

β Cell-specific deletion of Zfp148 improves nutrient-stimulated β cell Ca2+ responses

Insulin secretion from pancreatic β cells is essential for glucose homeostasis. An insufficient response to the demand for insulin results in diabetes. We previously showed that β cell-specific deletion of Zfp148 (β-Zfp148KO) improves glucose tolerance and insulin secretion in mice. Here, we performed Ca2+ imaging of islets from β‑Zfp148KO and control mice fed both a chow and a Western-style diet. β-Zfp148KO islets demonstrated improved sensitivity and sustained Ca2+ oscillations in response to elevated glucose levels. β-Zfp148KO islets also exhibited elevated sensitivity to amino acid-induced Ca2+ influx under low glucose conditions, suggesting enhanced mitochondrial phosphoenolpyruvate-dependent (PEP-dependent), ATP-sensitive K+ channel closure, independent of glycolysis. RNA-Seq and proteomics of β-Zfp148KO islets revealed altered levels of enzymes involved in amino acid metabolism (specifically, SLC3A2, SLC7A8, GLS, GLS2, PSPH, PHGDH, and PSAT1) and intermediary metabolism (namely, GOT1 and PCK2), consistent with altered PEP cycling. In agreement with this, β-Zfp148KO islets displayed enhanced insulin secretion in response to l-glutamine and activation of glutamate dehydrogenase. Understanding pathways controlled by ZFP148 may provide promising strategies for improving β cell function that are robust to the metabolic challenge imposed by a Western diet.

The Epstein-Barr Virus BMRF1 Protein Activates Transcription and Inhibits the DNA Damage Response by Binding NuRD

The BMRF1 protein of Epstein-Barr virus (EBV) has multiple roles in viral lytic infection, including serving as the DNA polymerase processivity factor, activating transcription from several EBV promoters and inhibiting the host DNA damage response to double-stranded DNA breaks (DSBs). Using affinity purification coupled to mass spectrometry, we identified the nucleosome remodeling and deacetylation (NuRD) complex as the top interactor of BMRF1. We further found that NuRD components localize with BMRF1 at viral replication compartments and that this interaction occurs through the BMRF1 C-terminal region previously shown to mediate transcriptional activation. We identified an RBBP4 binding motif within this region that can interact with both RBBP4 and MTA2 components of the NuRD complex and showed that point mutation of this motif abrogates NuRD binding as well as the ability of BMRF1 to activate transcription from the BDLF3 and BLLF1 EBV promoters. In addition to its role in transcriptional regulation, NuRD has been shown to contribute to DSB signaling in enabling recruitment of RNF168 ubiquitin ligase and subsequent ubiquitylation at the break. We showed that BMRF1 inhibited RNF168 recruitment and ubiquitylation at DSBs and that this inhibition was at least partly relieved by loss of the NuRD interaction. The results reveal a mechanism by which BMRF1 activates transcription and inhibits DSB signaling and a novel role for NuRD in transcriptional activation in EBV.IMPORTANCE The Epstein-Barr virus (EBV) BMRF1 protein is critical for EBV infection, playing key roles in viral genome replication, activation of EBV genes, and inhibition of host DNA damage responses (DDRs). Here we show that BMRF1 targets the cellular nucleosome remodeling and deacetylation (NuRD) complex, using a motif in the BMRF1 transcriptional activation sequence. Mutation of this motif disrupts the ability of BMRF1 to activate transcription and interfere with DDRs, showing the importance of the NuRD interaction for BMRF1 functions. BMRF1 was shown to act at the same step in the DDR as NuRD, suggesting that it interferes with NuRD function.

ZNF148 modulates TOP2A expression and cell proliferation via ceRNA regulatory mechanism in colorectal cancer

BACKGROUND

Competing endogenous RNA (ceRNA) regulation is a novel hypothesized mechanism that states RNA molecules share common target microRNAs (miRNAs) and may competitively combine into the same miRNA pool.

METHODS

Zinc finger protein 148 (ZNF148) and TOP2A expression were analyzed in 742 colorectal cancer (CRC) tissues using immunohistochemistry (IHC). ZNF148 mRNA, TOP2A mRNA, miR101, miR144, miR335, and miR365 expression were estimated in 53 fresh frozen CRC tissues by reverse transcription polymerase chain reaction. Mechanisms underpinning ceRNA were examined using bioinformatics, correlation analysis, RNA interference, gene over-expression, and luciferase assays.

RESULTS

Protein levels of ZNF148 and TOP2A detected by IHC positively correlated (Spearman correlation coefficient [rs] = 0.431, P < 0.001); mRNA levels of ZNF148 and TOP2A also positively correlated (r = 0.591, P < 0.001). Bioinformatics analysis demonstrated that ZNF148 and TOP2A mRNA had 13 common target miRNAs, including miR101, miR144, miR335, and miR365. Correlation analysis demonstrated that levels of ZNF148 mRNA were negatively associated with levels of miR144, miR335, and miR365. Knockdown and overexpression tests showed that ZNF148 mRNA and TOP2A mRNA regulated each other in HCT116 cells, respectively, but not in Dicer-deficient HCT116 cells. Luciferase assays demonstrated that ZNF148 and TOP2A regulated each other through 3'UTR. Overexpression of ZNF148 mRNA and TOP2A mRNA caused significant downregulation of miR101, miR144, miR335, and miR365 in the HCT116 cells. We also found that knockdown of ZNF148 and TOP2A significantly promoted cell growth, and overexpression of ZNF148 and TOP2A inhibited cell proliferation, which was abrogated in Dicer-deficient HCT116 cells.

CONCLUSION

ZNF148 and TOP2A regulate each other through ceRNA regulatory mechanism in CRC, which has biological effects on cell proliferation.

The functional interactome of PYHIN immune regulators reveals IFIX is a sensor of viral DNA

The human PYHIN proteins, AIM2, IFI16, IFIX, and MNDA, are critical regulators of immune response, transcription, apoptosis, and cell cycle. However, their protein interactions and underlying mechanisms remain largely uncharacterized. Here, we provide the interaction network for all PYHIN proteins and define a function in sensing of viral DNA for the previously uncharacterized IFIX protein. By designing a cell-based inducible system and integrating microscopy, immunoaffinity capture, quantitative mass spectrometry, and bioinformatics, we identify over 300 PYHIN interactions reflective of diverse functions, including DNA damage response, transcription regulation, intracellular signaling, and antiviral response. In view of the IFIX interaction with antiviral factors, including nuclear PML bodies, we further characterize IFIX and demonstrate its function in restricting herpesvirus replication. We discover that IFIX detects viral DNA in both the nucleus and cytoplasm, binding foreign DNA via its HIN domain in a sequence-non-specific manner. Furthermore, IFIX contributes to the induction of interferon response. Our results highlight the value of integrative proteomics in deducing protein function and establish IFIX as an antiviral DNA sensor important for mounting immune responses.

Expression of ZNF148 in different developing stages of colorectal cancer and its prognostic value: a large Chinese study based on tissue microarray

BACKGROUND

It has been speculated that zinc finger protein 148 (ZNF148) is a tumor suppressor. However, to the authors' knowledge, little is known about the clinical significance of ZNF148 expression in patients with colorectal cancer (CRC). The objective of the current study was to clarify the association between ZNF148 expression and the postoperative prognosis of patients with CRC.

METHODS

Tissue microarrays containing 56 normal mucosa, 51 adenoma, 742 CRC (TNM stage I-IV), 16 familial adenomatous polyposis, and 21 metastatic CRC specimens were examined immunohistochemically for ZNF148 expression.

RESULTS

Expression of ZNF148 was found to increase consecutively from normal mucosa to stage I CRC, and then decreased consecutively from stage I to stage IV CRC. Lower expression of ZNF148 in tumors was found to be significantly associated with lymph node metastases, advanced TNM disease stage, poor differentiation, higher rate of disease recurrence, worse overall survival (OS), and shorter disease-free survival. High expression of ZNF148 was also associated with improved OS (P = .025) and disease-free survival (P = .042) in patients with stages II to III CRC. On multivariate Cox analysis, lower ZNF148 expression in tumors, advanced TNM stage, colon cancer, and elevated serum carbohydrate antigen 19-9 (CA19-9) were found to be significant factors for a worse OS. In 16 patients with familial adenomatous polyposis, ZNF148 expression was upregulated at steps toward carcinogenesis. In 21 patients with metastatic CRC, although ZNF148 expression was higher in primary tumors compared with adjacent mucosa, its expression in metastatic tumors was significantly lower than that in primary tumors.

CONCLUSIONS

Although ZNF148 expression is related to colorectal carcinogenesis, high ZNF148 expression in patients with CRC appears to be inversely associated with malignant phenotypes and may serve as a significant prognostic factor after surgery for patients with CRC.

Promoter cloning and characterization of the human programmed cell death protein 4 (pdcd4) gene: evidence for ZBP-89 and Sp-binding motifs as essential Pdcd4 regulators

Pdcd4 (programmed cell death protein 4) is an important novel tumour suppressor inhibiting transformation, translation, invasion and intravasation, and its expression is down-regulated in several cancers. However, little is known about the transcriptional regulation and the promoter of this important tumour suppressor. So far the following is the first comprehensive study to describe the regulation of Pdcd4 transcription by ZBP-89 (zinc-finger-binding protein 89), besides characterizing the gene promoter. We identified the transcriptional start sites of the human pdcd4 promoter, a functional CCAAT-box, and the basal promoter region. Within this basal region, computer-based analysis revealed several potential binding sites for ZBPs, especially for Sp (specificity protein) family members and ZBP-89. We identified four Sp1/Sp3/Sp4-binding elements to be indispensable for basal promoter activity. However, overexpression of Sp1 and Sp3 was not sufficient to enhance Pdcd4 protein expression. Analysis in different solid cancer cell lines showed a significant correlation between pdcd4 and zbp-89 mRNA amounts. In contrast with Sp transcription factors, overexpression of ZBP-89 led to an enhanced expression of Pdcd4 mRNA and protein. Additionally, specific knockdown of ZBP-89 resulted in a decreased pdcd4 gene expression. Reporter gene analysis showed a significant up-regulation of basal promoter activity by co-transfection with ZBP-89, which could be abolished by mithramycin treatment. Predicted binding of ZBP-89 to the basal promoter was confirmed by EMSA (electrophoretic mobility-shift assay) data and supershift analysis for ZBP-89. Taken together, data for the first time implicate ZBP-89 as a regulator of Pdcd4 by binding to the basal promoter either alone or by interacting with Sp family members.

Transcription factor ZBP-89 in cancer growth and apoptosis

ZBP-89, a Krüppel-type zinc-finger transcription factor that binds to GC-rich sequences, is involved in the regulation of cell growth and cell death. It maps to chromosome 3q21 and is composed of 794 residues. Having bifunctional regulatory domains, ZBP-89 may function as a transcriptional activator or repressor of variety of genes such as p16 and vimentin. ZBP-89 arrests cell proliferation through its interactions with p53 and p21(waf1). It is able to stabilize p53 through directly binding and enhance p53 transcriptional activity by retaining it in the nucleus. In addition, ZBP-89 potentiates in butyrate-induced endogenous p21(waf1) up-regulation. ZBP-89 is usually over-expressed in human cancer cells, where it can efficiently induce apoptosis through p53-dependent and -independent mechanisms. Moreover, ZBP-89 is capable of enhancing killing effects of several anti-cancer drugs. Therefore, ZBP-89 may be served as a potential target in cancer therapy.

Discovery of porcine microRNAs and profiling from skeletal muscle tissues during development

MiRNAs (microRNAs) play critical roles in many important biological processes such as growth and development in mammals. In this study, we identified hundreds of porcine miRNA candidates through in silico prediction and analyzed their expression in developing skeletal muscle using microarray. Microarray screening using RNA samples prepared from a 33-day whole embryo and an extra embryo membrane validated 296 of the predicted candidates. Comparative expression profiling across samples of longissimus muscle collected from 33-day and 65-day post-gestation fetuses, as well as adult pigs, identified 140 differentially expressed miRNAs amongst the age groups investigated. The differentially expressed miRNAs showed seven distinctive types of expression patterns, suggesting possible involvement in certain biological processes. Five of the differentially expressed miRNAs were validated using real-time PCR. In silico analysis of the miRNA-mRNA interaction sites suggested that the potential mRNA targets of the differentially expressed miRNAs may play important roles in muscle growth and development.

ZBP-89 and Sp3 down-regulate while NF-Y up-regulates SOX18 promoter activity in HeLa cells

The aim of this study has been to identify transcription factors involved in transcriptional regulation of the human SOX18 gene expression. Structural analysis revealed that the SOX18 promoter lacks a TATA box, but is CG-rich containing many putative binding sites for transcription factors that can bind and act through GC-boxes. Alignment analysis of promoter regions between human and mouse revealed conserved putative binding sites for transcription factors NF-Y and Sp-family members. Mithramycin A treatment led to increased SOX18 expression in vivo raising the possibility that the GC-rich sequence of the human SOX18 promoter might be occupied by transcription factor(s) that acts as repressor(s). Using in vitro binding assays we have demonstrated that transcription factors Sp3, ZBP-89 and NF-Y are capable of binding to the SOX18 promoter region spanning the sequence -200 to -162 relative to ATG and that formation of complexes could be efficiently reduced by mithramycin A. Furthermore, co-transfection experiments revealed that over-expression of Sp3 and ZBP-89 down-regulate, while over-expression of NF-Y up-regulates SOX18 promoter activity in HeLa cells. The involvement of these transcription factors in the regulation of SOX18 expression in HeLa cells was further confirmed in vivo by Western blot analyses. In this paper, for the first time, we have demonstrated that Sp3, ZBP-89 and NF-Y are involved in transcriptional regulation of the human SOX18 gene expression. Presented data provide the initial information about transcriptional regulation that will help in better understanding of molecular mechanisms involved in regulation of SOX18 gene expression.

Sumoylation-dependent control of homotypic and heterotypic synergy by the Kruppel-type zinc finger protein ZBP-89

The Krüppel-like transcription factor ZBP-89 is a sequence-specific regulator that plays key roles in cellular growth and differentiation especially in endodermal and germ cell lineages. ZBP-89 shares with other members of the Sp-like family an overlapping sequence specificity for GC-rich sequences in the regulatory regions of multiple genes. Defining the mechanisms that govern the intrinsic function of ZBP-89 as well as its competitive and non-competitive functional interactions with other regulators is central to understand how ZBP-89 exerts its biological functions. We now describe that post-translational modification of ZBP-89 by multiple small ubiquitin-like modifier (SUMO) isoforms occurs at two conserved synergy control motifs flanking the DNA binding domain. Functionally sumoylation did not directly alter the ability of ZBP-89 to compete with other Sp-like factors from individual sites. At promoters bearing multiple response elements, however, this modification inhibited the functional cooperation between ZBP-89 and Sp1. Analysis of the properties of ZBP-89 in cellular contexts devoid of competing factors indicated that although on its own it behaves as a modest activator it potently synergizes with heterologous activators such as the glucocorticoid receptor. Notably we found that when conjugated to ZBP-89, SUMO exerts a strong inhibitory effect on such synergistic interactions through a critical conserved functional surface. By regulating higher order functional interactions, sumoylation provides a reversible post-translational mechanism to control the activity of ZBP-89.

Intestinal overexpression of ZNF148 suppresses ApcMin/+ neoplasia

ZNF148 (ZBP-89, Zfp148) is a multifunctional transcription factor expressed at low levels in most tissues. When overexpressed in gastrointestinal cancer cell lines, ZNF148 inhibits cellular proliferation and induces apoptosis. We sought to determine whether intestinal ZNF148 overexpression would abrogate adenoma development in the ApcMin/+ mouse, i.e., whether ZNF148 is a tumor suppressor. The 13-kb villin promoter was spliced upstream of the ZNF148 cDNA to generate transgenic villin-ZNF148 (ZNF148TgVZ) mice. Intestinal mucosal ZNF148 expression was elevated in four of five ZNF148(TgVZ) lineages and correlated with increased caspase-3 expression and activation. In addition, DNA fragmentation was increased in ZNF148TgVZ mice relative to wild-type littermates. These results suggested that increased intestinal ZNF148 expression induces apoptosis. ZNF148TgVZ mice were crossed with ApcMin/+ mice to assess the biological significance of intestinal ZNF148 overexpression. The presence of the ZNF148TgVZ allele in ApcMin/+ mice correlated with reduced gastrointestinal bleeding at 5 weeks, a 50% reduction in adenoma burden at 20-22 weeks, and prolonged survival (median survival of 33.5 days vs. 21.5 days), relative to nontransgenic littermates. These data suggest that enhanced ZNF148 expression activates intestinal apoptosis and thereby mitigates disease burden in ApcMin/+ mice. They also suggest that ZNF148 is a therapeutic target to inhibit colon cancer development.

A PDGFRA promoter polymorphism, which disrupts the binding of ZNF148, is associated with primitive neuroectodermal tumours and ependymomas

BACKGROUND

Platelet derived growth factor receptor alpha (PDGFRalpha) expression is typical for a variety of brain tumours, while in normal adult brain PDGFRalpha expression is limited to a small number of neural progenitor cells. The molecular mechanisms responsible for the PDGFRalpha expression in tumours are not known, but in the absence of amplification, changes in transcriptional regulation might be an important factor in this process.

METHODS AND RESULTS

We have investigated the link between single nucleotide polymorphisms (SNPs) within the PDGFRalpha gene promoter and the occurrence of brain tumours (medulloblastomas, supratentorial primitive neuroectodermal tumours (PNETs), ependymal tumours, astrocytomas, oligodendrogliomas, and mixed gliomas). These SNPs give rise to five different promoter haplotypes named H1 and H2alpha-delta. It is apparent from the haplotype frequency distribution that both PNET (10-fold) and ependymoma (6.5-fold) patient groups display a significant over-representation of the H2delta haplotype. The precise functional role in PDGFRalpha gene transcription for the H2delta haplotype is not known yet, but we can show that the H2delta haplotype specifically disrupts binding of the transcription factor ZNF148 as compared to the other promoter haplotypes.

CONCLUSIONS

The specific over-representation of the H2delta haplotype in both patients with PNETs and ependymomas suggests a functional role for the ZNF148/PDGFRalpha pathway in the pathogenesis of these tumours.

An isoform of ZBP-89 predisposes the colon to colitis

Alternative splicing enables expression of functionally diverse protein isoforms. The structural and functional complexity of zinc-finger transcription factor ZBP-89 suggests that it may be among the class of alternatively spliced genes. We identified a human ZBP-89 splice isoform (ZBP-89(DeltaN)), which lacks amino terminal residues 1-127 of the full-length protein (ZBP-89(FL)). ZBP-89(DeltaN) mRNA was co-expressed with its ZBP-89(FL) cognate in gastrointestinal cell lines and tissues. Similarly, ZBP-89(DeltaN) protein was expressed. To define its function in vivo, we generated ZBP-89(DeltaN) knock-in mice by targeting exon 4 that encodes the amino terminus. Homozygous ZBP-89(DeltaN) mice, expressing only ZBP-89(DeltaN) protein, experienced growth delay, reduced viability and increased susceptibility to dextran sodium sulfate colitis. We conclude that ZBP-89(DeltaN) antagonizes ZBP-89(FL) function and that over-expression of the truncated isoform disrupts gastrointestinal homeostasis.

The Epstein-Barr virus protein BMRF1 activates gastrin transcription

The Epstein-Barr virus (EBV) BMRF1 gene encodes an early lytic protein that functions not only as the viral DNA polymerase processivity factor but also as a transcriptional activator. BMRF1 has been previously shown to activate transcription of an EBV early promoter, BHLF1, though a GC-rich motif which binds to SP1 and ZBP-89, although the exact mechanism for this effect is not known (D. J. Law, S. A. Tarle, and J. L. Merchant, Mamm. Genome 9:165-167, 1998). Here we demonstrate that BMRF1 activates transcription of the cellular gastrin gene in telomerase-immortalized keratinocytes. Furthermore, BMRF1 activated a reporter gene construct driven by the gastrin promoter in a variety of cell types, and this effect was mediated by two SP1/ZBP-89 binding sites in the gastrin promoter. ZBP-89 has been previously shown to negatively regulate the gastrin promoter. However, ZBP-89 can function as either a negative or positive regulator of transcription, depending upon the promoter and perhaps other, as-yet-unidentified factors. BMRF1 increased the binding of ZBP-89 to the gastrin promoter, and a ZBP-89-GAL4 fusion protein was converted into a positive transcriptional regulator by cotransfection with BMRF1. BMRF1 also enhanced the transcriptional activity of an SP1-GAL4 fusion protein. These results suggest that BMRF1 activates target promoters through its effect on both the SP1 and ZBP-89 transcription factors. Furthermore, as the EBV genome is present in up to 10% of gastric cancers, and the different forms of gastrin are growth factors for gastrointestinal epithelium, our results suggest a mechanism by which lytic EBV infection could promote the growth of gastric cells.

Stat3 enhances vimentin gene expression by binding to the antisilencer element and interacting with the repressor protein, ZBP-89

Vimentin exhibits a complex pattern of developmental- and tissue-specific expression and is aberrantly expressed in most metastatic tumors. The human vimentin promoter contains multiple DNA elements, some of which enhance gene expression and one that inhibits. A silencer element (at -319) binds the repressor ZBP-89. Further upstream (at -757) is an element, which acts positively in the presence of the silencer element and, thus, is referred to as an antisilencer (ASE). Previously, we showed that Stat1alpha binds to this element upon induction by IFN-gamma. However, substantial binding and reporter gene activity was still present in nontreated cells. Here, we have found that Stat3 binds to the ASE element in vitro. Transfection experiments in COS-1 cells with various vimentin promoter--reporter constructs show that gene activity is dependent upon the cotransfection and activation of Stat3. Moreover, activated Stat3 can overcome ZBP-89 repression. Coimmunoprecipitation studies demonstrate that Stat3 and ZBP-89 can interact and confocal microscopy detects these factors to be colocalized in the nucleus. Moreover, a correlation exists between the presence of activated Stat3 and vimentin expression in MDA-MB-231 cells, which is lacking in MCF7 cells where vimentin is not expressed. In the light of these results, we propose that the interaction of Stat3 and ZBP-89 may be crucial for overcoming the effects of the repressor ZBP-89, which suggests a novel mode for Stat3 gene activation.

ZBP-89 mediates butyrate regulation of gene expression

Inducible p53-independent regulation of the cyclin-dependent kinase inhibitor p21(Waf1) transcription is mediated through its proximal GC-rich sites. Prior studies have shown that Sp1, Sp3 and the histone acetyltransferase coactivator p300 are components of the complexes that bind to these sites. Although Sp1 and Sp3 collaborate with p300, a direct interaction between Sp1 and p300 does not occur. Zinc-finger binding protein-89 (ZBP-89, also known as BFCOL1, BERF-1 and ZNF-148) is a Krüppel-type zinc-finger transcription factor that binds to the same GC-rich sequences as Sp1. We sought to determine whether ZBP-89 is a target of p300 during butyrate induction of p21(Waf1). This review summarizes the evidence that supports a crucial role for ZBP-89 in butyrate regulation of p21(Waf1). Adenovirus-mediated expression of ZBP-89 in HT-29 cells reveals that ZBP-89 potentiates butyrate induction of endogenous p21(Waf1) gene expression. DNA-protein interaction assays demonstrate that Sp1, Sp3 and ZBP-89 bind the p21(Waf1) promoter at -245 to -215. Coprecipitation assays reveal that p300 preferentially binds to the N-terminus of ZBP-89. ZBP-89 also induces p21(Waf1) through stabilization of p53. Although ZBP-89 binds mutant and wild-type p53, only wild-type p53 is stabilized. Moreover, mutant p53 shifts the subnuclear location of ZBP-89 to the nuclear periphery, which is a domain rich in heterochromatin. This finding led to the conclusion that mutant p53 exerts a dominant negative effect on ZBP-89. We propose that gene silencing by mutant p53 might be mediated by sequestering ZBP-89 within heterochromatin regions at the nuclear periphery. Overall, ZBP-89 is a butyrate-regulated coactivator of p53 and is able to induce p21(Waf1) gene expression through both p53-dependent and -independent mechanisms to inhibit cell growth.

ZBP-89 represses vimentin gene transcription by interacting with the transcriptional activator, Sp1

Vimentin, a member of the intermediate filament protein family, is regulated both developmentally and tissue specifically. It is also a marker of the metastatic potential of many tumor cells. Pre viously, the human vimentin promoter has been shown to contain multiple elements for the binding of both positive- and negative-acting regulatory factors. Transient transfection analysis of various vimentin 5'-end promoter sequences and mutants thereof fused to a reporter gene further defined two regulatory elements, a positive element that binds Sp1 and a negative element that binds the protein ZBP-89. ZBP-89 has been shown to be either a repressor or an activator of gene expression, depending on the promoter. Here, we show that for vimentin, both ZBP-89 and ZBP-99 repress reporter gene expression in Schneider (S2) cells. Deletion constructs confirm that the glutamine-rich region of Sp1 is required to enhance vimentin transcription, whereas the N-terminus of ZBP-89 is required to interact with Sp1 and repress gene expression. The overexpression of hTAF(II)130 can alleviate ZBP-89 repression in S2 cells, suggesting how ZBP-89 might serve to block gene expression.

The zinc finger transcription factor ZBP-89 is a repressor of the human beta 2-integrin CD11b gene

Integrin CD11b is a differentiation marker of the myelomonocytic lineage and an important mediator of inflammation. Expression of the CD11b gene is transcriptionally induced as myeloid precursors differentiate into mature cells, then drops as monocytes further differentiate into macrophages. Previous studies have identified elements and factors involved in the transcriptional activation of the CD11b gene during myeloid differentiation, but no data exist regarding potential down-regulatory factors, especially in the later stages of differentiation. Using 2 copies of a GC-rich element (-141 to -110) in the CD11b promoter, we probed a cDNA expression library for interacting proteins. Three clones were identified among 9.1 million screened, all encoding the DNA-binding domain of the zinc finger factor ZBP-89. Overexpression of ZBP-89 in the monocyte precursor cell line U937 reduced CD11b promoter-driven luciferase activity when U937 cells were induced to differentiate into monocytelike cells using phorbol esters. To identify the differentiation stage at which ZBP-89 repression of the CD11b gene is exerted, the protein level of ZBP-89 was correlated with that of CD11b mRNA in differentiating U937 as well as in normal human monocytes undergoing in vitro differentiation into macrophages. A clear inverse relationship was observed in the latter but not the former state, suggesting that ZBP-89 represses CD11b gene expression during the further differentiation of monocytes into macrophages.

Integration of porcine chromosome 13 maps

In order to expand the comparative map between human chromosome 3 (HSA3) and porcine chromosome 13 (SSC13), seven genes from HSA3 were mapped on SSC13 by fluorescence in situ hybridisation (FISH), viz. ACAA1, ACPP, B4GALT4, LTF, MYLK, PDHB and RARB. With a view to integrating this expanded comparative map with the existing SSC13 linkage map, we used the INRA-University of Minnesota porcine Radiation Hybrid panel (IMpRH) to localize more precisely and to order 15 genes on the SSC13 map, viz. ACPP, ADCY5, APOD, BCHE, CD86, DRD3, GAP43, PCCB, RAF1, RHO, SI, TF, TFRC, TOP2B and ZNF148. In this way, we were able to create an integrated map, containing 38 type I and 81 type II markers, by correlating the linkage, radiation hybrid (RH) and cytogenetic maps of SSC13. This integrated map will give us the opportunity to take maximal advantage of the comparative mapping strategy for positional candidate cloning of genes responsible for economically important traits.

Conserved structure and promoter sequence similarity in the mouse and human genes encoding the zinc finger factor BERF-1/BFCOL1/ZBP-89

We have characterized the genomic structure of the mouse Zfp148 gene encoding Beta-Enolase Repressor Factor-1 (BERF-1), a Kruppel-like zinc finger protein involved in the transcriptional regulation of several genes, which is also termed ZBP-89, BFCOL1. The cloned Zfp148 gene spans 110 kb of genomic DNA encompassing the 5'-end region, 9 exons, 8 introns, and the 3'-untranslated region. The promoter region displays the typical features of a housekeeping gene: a high G+C content and the absence of canonical TATA and CAAT boxes consistent with the multiple transcription initiation sites determined by primary extension analysis. Computer-assisted search in the human genome database allowed us to determine that the same genomic structure with identical intron-exon organization is conserved in the human homologue ZNF 148. Functional analysis of the 5'-flanking sequence of the mouse gene indicated that the region from nucleotide -205 to +144, relative to the major transcription start site, contains cis-regulatory elements that promote basal expression. Such sequences and the overall promoter architecture are highly conserved in the human gene. Furthermore, we show that the complex transcription pattern of the Zfp148 gene might be due to a combination of alternative splicing and differential polyadenylation sites utilization.

Transcription factor ZBP-89 cooperates with histone acetyltransferase p300 during butyrate activation of p21waf1 transcription in human cells

Inducible p53-independent regulation of the cyclin-dependent kinase inhibitor p21(waf1) transcription is mediated through proximal GC-rich sites. Prior studies have shown that Sp1, Sp3, and the histone acetylase co-activator p300 are components of the complexes binding to these sites. Although Sp1 and Sp3 collaborate with p300, a direct interaction between Sp1 and p300 does not occur. This study sought to determine whether ZBP-89 rather than Sp1 is the direct target of p300 during butyrate induction of p21(waf1). ZBP-89 (BFCOL1, BERF-1, ZNF 148) is a Krüppel-type zinc finger transcription factor that binds to GC-rich elements and represses or activates known target genes. Adenoviral-mediated expression of ZBP-89 in HT-29 cells revealed that ZBP-89 potentiates butyrate induction of endogenous p21(waf1) gene expression. Further, cotransfection of a ZBP-89 expression vector with a 2.3-kilobase p21(waf1) reporter recapitulated the potentiation by butyrate. DNase I footprinting analysis of the human p21(waf1) promoter with recombinant ZBP-89 identified a binding site at -245 to -215. Electrophoretic mobility shift assays confirmed that both recombinant and endogenous ZBP-89 and Sp1 bind to this element. The potentiation was abolished in the presence of adenoviral protein E1A. Deletion of the N-terminal domain of ZBP-89 abolished the potentiation mediated by butyrate treatment. This same deletion mutant abolished the ZBP-89 interaction with p300. Cotransfection of p300 with ZBP-89 stimulated the p21(waf1) promoter in the absence of butyrate. p300 co-precipitated with ZBP-89 but not with Sp1, whereas ZBP-89 co-precipitated with Sp1. Together, these findings demonstrate that ZBP-89 also plays a critical role in butyrate activation of the p21(waf1) promoter and reveals preferential cooperation of this four-zinc finger transcription factor with p300.

The gene encoding the transcriptional repressor BERF-1 maps to a region of conserved synteny on mouse chromosome 16 and human chromosome 3 and a related pseudogene maps to mouse chromosome 8

We have recently identified and characterized a Kruppel-like zinc finger protein (BERF-1), that functions as a repressor of beta enolase gene transcription. By interspecific backcross analysis the gene encoding BERF-1 was localized 4.7 cM proximal to the Mtv6 locus on mouse chromosome 16, and an isolated pseudogene was localized to mouse chromosome 8, about 5.3 cM distal to the D8Mit4 marker. Nucleotide sequence identity and chomosome location indicate that the gene encoding BERF-1 is the mouse homologue (Zfp148) of ZNF148 localized to human chromosome 3q21, a common translocation site in acute myeloid leukemia patients.

ZBP-99 defines a conserved family of transcription factors and regulates ornithine decarboxylase gene expression

Among transcription factors that regulate ornithine decarboxylase (ODC) gene expression are those that interact with GC-rich promoters, including Sp1 and ZBP-89. Sp1 functions as a transactivator and ZBP-89 as a transrepressor of both the ODC and gastrin promoters. This study reports the cloning and characterization of a second member of the ZBP family that also binds GC boxes. ZBP-99 contains four Krüppel-type zinc fingers that collectively share 91% amino acid sequence similarity and 79% sequence identity with those found in ZBP-89. In addition, there are highly conserved amino acid sequences in the carboxy-terminal segments of the two genes. In spite of their structural similarities, the two proteins are encoded at distinct loci, ZBP-89 on chromosome 3q21 and ZBP-99 on 1q32.1. The predicted open reading frame of ZBP-99 cDNA encodes a 99-kDa protein. Electrophoretic mobility shift assays showed that ZBP-99 protein specifically binds to the GC-rich promoter elements of gastrin and ODC genes. Northern blot analysis showed that a major ZBP-99 transcript of 5.6 kb is expressed ubiquitously at low levels, with elevated expression levels in placenta and in adult kidney, liver, and lymphocytes. Cotransfection of AGS gastric adenocarcinoma and HT-29 colon adenocarcinoma cells with a ZBP-99 expression construct and with an ODC reporter construct show that ZBP-99 repressed basal expression in the two cell lines by 80 and 60%, respectively. Collectively, the data suggest that ZBP-99 binds GC-rich promoters and may complement the activities mediated by ZBP-89.

Identification of human GC-box-binding zinc finger protein, a new Krüppel-like zinc finger protein, by the yeast one-hybrid screening with a GC-rich target sequence

A new human zinc finger DNA-binding protein was identified by using a yeast one-hybrid selection system. Two versions of the cDNA, encoding the same protein, were detected that differ for a 584 bp extension at the 5' region. Sequence analysis showed that the longer clone is a full length version containing part of the 5' untranslated region. The smaller version was fused in frame with the yeast GAL4 activation domain whereas the 5' region of the longer clone displayed a stop codon interrupting the fusion with the GAL4 domain. Nevertheless, this clone activated the yeast HIS3 reporter gene with the same efficiency as the smaller version. Sequence comparison of the derived protein with the database showed that it belongs to a family of zinc finger DNA-binding proteins which regulate the expression of genes involved in cell proliferation. Expression of the protein in an in vitro system, DNA-binding studies and genetic experiments identify this factor as a new zinc finger DNA-binding protein which binds GC-rich sequences and contains a domain probably functioning as a transcriptional activator. The new human protein identified in this study was therefore named GC-box-binding zinc finger protein).

Expression of the mouse pre-T cell receptor alpha gene is controlled by an upstream region containing a transcriptional enhancer

The pre-T cell receptor alpha (pTalpha) protein is a critical component of the pre-T cell receptor complex in early thymocytes. The expression of the pTalpha gene is one of the earliest markers of the T cell lineage and occurs exclusively in pre-T cells. To investigate the molecular basis of thymocyte-specific gene expression, we searched for the genomic elements regulating transcription of the mouse pTalpha gene. We now report that expression of the pTalpha gene is primarily controlled by an upstream genomic region, which can drive thymocyte-specific expression of a marker gene in transgenic mice. Within this region, we have identified two specific DNase-hypersensitive sites corresponding to a proximal promoter and an upstream transcriptional enhancer. The pTalpha enhancer appears to function preferentially in pre-T cell lines and binds multiple nuclear factors, including YY1. The enhancer also contains two G-rich stretches homologous to a critical region of the thymocyte-specific lck proximal promoter. Here we show that these sites bind a common nuclear factor and identify it as the zinc finger protein ZBP-89. Our data establish a novel experimental model for thymocyte-specific gene expression and suggest an important role for ZBP-89 in T cell development.

Human stromelysin gene promoter activity is modulated by transcription factor ZBP-89

Matrix metalloproteinase expression is under strict regulation in physiological conditions. Disruption of the regulatory mechanisms can lead to tissue destruction and is associated with tumour invasion and metastasis. Using the one-hybrid assay technique with a cis-element in the promoter region of the stromelysin (matrix metalloproteinase-3) gene, a cDNA encoding a transcription factor termed ZBP-89 was obtained. The interaction between ZBP-89 and the stromelysin promoter element was confirmed by electrophoretic mobility shift assays with a recombinant ZBP-89. Reporter gene expression under the control of the stromelysin promoter in transiently transfected cells was significantly increased when the cells were cotransfected with a ZBP-89 expression construct. These results indicate that ZBP-89 interacts with the stromelysin promoter and upregulates its activity. As ZBP-89 expression is known to be increased in gastric carcinoma cells, induction of stromelysin expression may be a significant factor in tumour metastasis.