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Results for “Enhancer Elements, Genetic”

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PubMed2001

Ectopic expression of MAFB gene in human myeloma cells carrying (14;20)(q32;q11) chromosomal translocations.

Chromosome 14q +, which represents a chromosomal rearrangement involving the immunoglobulin heavy chain gene (IgH) locus, is a genetic hallmark of human multiple myeloma (MM). Here, we report the identification of (14;20)(q32;q11) chromosomal translocations found in MM cells. Double color fluorescence in situ hybridization analyses pinpointed the breakpoints at the 20q11 locus in two MM cell lines within a length of at most 680 kb between the KIAA0823 and MAFB gene loci. Among the transcribed sequences in the vicinity of the breakpoints, an ectopic expression of the MAFB gene, which is located at 450 - 680 kb telomeric to one of the breakpoints and encodes a member of the MAF family basic region / leucine zipper transcription factor, was demonstrated to be associated with t(14;20). This finding, together with that of a previous study describing its transforming activity, suggests that the MAFB gene may be one of the targets deregulated by regulatory elements of the IgH gene as a result of t(14;20).

Avian Proteins↗

PubMed2005

Requirements of genetic interactions between Src42A, armadillo and shotgun, a gene encoding E-cadherin, for normal development in Drosophila.

Src42A is one of the two Src homologs in Drosophila. Src42A protein accumulates at sites of cell-cell or cell-matrix adhesion. Anti-Engrailed antibody staining of Src42A protein-null mutant embryos indicated that Src42A is essential for proper cell-cell matching during dorsal closure. Src42A, which is functionally redundant to Src64, was found to interact genetically with shotgun, a gene encoding E-cadherin, and armadillo, a Drosophila beta-catenin. Immunoprecipitation and a pull-down assay indicated that Src42A forms a ternary complex with E-cadherin and Armadillo, and that Src42A binds to Armadillo repeats via a 14 amino acid region, which contains the major autophosphorylation site. The leading edge of Src mutant embryos exhibiting the dorsal open phenotype was frequently kinked and associated with significant reduction in E-cadherin, Armadillo and F-actin accumulation, suggesting that not only Src signaling but also Src-dependent adherens-junction stabilization would appear likely to be essential for normal dorsal closure. Src42A and Src64 were required for Armadillo tyrosine residue phosphorylation but Src activity may not be directly involved in Armadillo tyrosine residue phosphorylation at the adherens junction.

Adherens Junctions↗

PubMedDate not supplied

Pulmonary carcinogenesis in transgenic mice.

Use of genetically engineered mice offers a unique approach to identifying and investigating factors that may influence tumor development. We have used conventional histopathologic and ultrastructural techniques to characterize lung tumors in three lines of transgenic mice bearing an albumin enhancer/promoter linked to a mutated human H-ras gene. Mice in all three lines developed multiple alveolar-bronchiolar (A/B) adenocarcinomas that are eventually lethal. The large diversity in tumor morphological features and differential tumor growth rates suggests that secondary events contribute to tumor phenotype and biological behavior. Two of the transgenic lines developed numerous A/B neoplasms within 6 to 8 weeks and thus may be useful animal models for testing potential anticancer chemotherapeutic agents. The other line lived for approximately 10 months, had fewer A/B tumors, but also developed bronchiogenic tumors. All three transgenic lines may be useful models for studying factors that affect lung tumor development.

Albumins↗

PubMed1997

In vivo footprinting with limiting amounts of embryo tissues: a role for C/EBP beta in early hepatic development.

Regulatory factors important for the developmental control of genes have been identified by genetic studies or by examining the ontological expression profiles of proteins that were originally characterized in adult tissues; direct biochemical studies of transcription factors within small amounts of embryo tissues have been limited. We have found that the ligation-mediated PCR (LM-PCR) technique can detect specific dimethylsulfate modifications in genomic DNA from as few as several thousand cells, making it technically feasible to identify protein-DNA interactions in pools of nascent embryo tissues. Herein we show that LM-PCR can reveal methylation protections on the albumin gene enhancer in embryonic mouse hepatocytes, indicating occupancy of a C/EBP factor binding site. Comparison of the in vivo protection pattern with that obtained from the in vitro analysis of different C/EBP isoforms suggests that in embryonic hepatocytes, C/EBP beta is bound to the albumin gene enhancer. Detailed protocols are provided so that the approach can be used to study other genes in developing embryos.

Animals↗

PubMed1995

Genetic characterization and cloning of mothers against dpp, a gene required for decapentaplegic function in Drosophila melanogaster.

The decapentaplegic (dpp) gene of Drosophila melanogaster encodes a growth factor that belongs to the transforming growth factor-beta (TGF-beta) superfamily and that plays a central role in multiple cell-cell signaling events throughout development. Through genetic screens we are seeking to identify other functions that act upstream, downstream or in concert with dpp to mediate its signaling role. We report here the genetic characterization and cloning of Mothers against dpp (Mad), a gene identified in two such screens. Mad loss-of-function mutations interact with dpp alleles to enhance embryonic dorsal-ventral patterning defects, as well as adult appendage defects, suggesting a role for Mad in mediating some aspect of dpp function. In support of this, homozygous Mad mutant animals exhibit defects in midgut morphogenesis, imaginal disk development and embryonic dorsal-ventral patterning that are very reminiscent of dpp mutant phenotypes. We cloned the Mad region and identified the Mad transcription unit through germline transformation rescue. We sequenced a Mad cDNA and identified three Mad point mutations that alter the coding information. The predicted MAD polypeptide lacks known protein motifs, but has strong sequence similarity to three polypeptides predicted from genomic sequence from the nematode Caenorhabditis elegans. Hence, MAD is a member of a novel, highly conserved protein family.

Amino Acid Sequence↗

PubMed2002

A genetic screen for suppressors and enhancers of the Drosophila cdk1-cyclin B identifies maternal factors that regulate microtubule and microfilament stability.

Coordination between cell-cycle progression and cytoskeletal dynamics is important for faithful transmission of genetic information. In early Drosophila embryos, increasing maternal cyclin B leads to higher Cdk1-CycB activity, shorter microtubules, and slower nuclear movement during cycles 5-7 and delays in nuclear migration to the cortex at cycle 10. Later during cycle 14 interphase of six cycB embryos, we observed patches of mitotic nuclei, chromosome bridges, abnormal nuclear distribution, and small and large nuclei. These phenotypes indicate disrupted coordination between the cell-cycle machinery and cytoskeletal function. Using these sensitized phenotypes, we performed a dosage-sensitive genetic screen to identify maternal proteins involved in this process. We identified 10 suppressors classified into three groups: (1) gene products regulating Cdk1 activities, cdk1 and cyclin A; (2) gene products interacting with both microtubules and microfilaments, Actin-related protein 87C; and (3) gene products interacting with microfilaments, chickadee, diaphanous, Cdc42, quail, spaghetti-squash, zipper, and scrambled. Interestingly, most of the suppressors that rescue the astral microtubule phenotype also reduce Cdk1-CycB activities and are microfilament-related genes. This suggests that the major mechanism of suppression relies on the interactions among Cdk1-CycB, microtubule, and microfilament networks. Our results indicate that the balance among these different components is vital for normal early cell cycles and for embryonic development. Our observations also indicate that microtubules and cortical microfilaments antagonize each other during the preblastoderm stage.

Actin Cytoskeleton↗

PubMed1996

Identification of a functional cAMP response element in the secretogranin II gene.

Secretogranin II is an acidic secretory protein with a widespread distribution in secretory granules of neuronal and endocrine cells. The secretogranin II gene contains, like other members of the granin family, a cAMP response element (CRE) in its upstream region. To investigate the functional significance of this motif, intracellular cAMP levels were increased in a neuronal cell line derived from the septal region of the brain and the level of secretogranin II gene expression was analysed. It was found that increased cAMP levels did, in fact, induce secretogranin II gene expression. To analyse the cis-acting sequence responsible for this induction, a hybrid gene containing the upstream region of the mouse secretogranin II gene fused to beta-globin as a reporter was constructed. Transfection analysis revealed that cAMP-induced transcription of the secretogranin II promoter/beta-globin gene in septal and insulinoma cells. DNA-protein binding assays showed that recombinant CRE-binding protein (CREB), produced in bacteria or human cells, bound in a sequence-specific manner to the secretogranin II promoter CRE. Moreover, deletion mutagenesis revealed that the CRE motif is a bifunctional genetic regulatory element in that it mediates basal as well as cAMP-stimulated transcription. Interestingly, cAMP had no effect upon secretogranin II gene transcription in PC12 and neuroblastoma cells. An increase in the intracellular cAMP concentration activated a GAL4-CREB fusion protein upon transcription in neuroblastoma cells indicating the integrity of the cAMP signaling pathway to the nucleus. Basal as well as cAMP-stimulated transcription, directed from the secretogranin II promoter was, however, impaired in insulinoma cells by overexpression of CREB-2, a negative-acting CRE-binding protein. These results indicate that competitive effects are likely to occur between CRE-bound transcriptional activators and repressors. We conclude that cAMP-stimulated induction of secretogranin II gene transcription is mediated by the CRE motif in a cell-type-specific manner, and is likely to depend on the balance between positive and negative CRE-binding proteins in a particular cell type.

1-Methyl-3-isobutylxanthine↗

PubMed2001

Molecular integration of inductive and mesoderm-intrinsic inputs governs even-skipped enhancer activity in a subset of pericardial and dorsal muscle progenitors.

Individual somatic muscles and heart progenitors are specified at defined positions within the mesodermal layer of Drosophila. The expression of the homeobox gene even-skipped (eve) identifies one specific subset of cells in the dorsal mesoderm, which give rise to particular pericardial cells and dorsal body wall muscles. Genetic analysis has shown that the induction of eve in these cells involves the combined activities of genes encoding mesoderm-intrinsic factors, such as Tinman (Tin), and spatially restricted signaling activities that are largely derived from the ectoderm, particularly those encoded by wingless (wg) and decapentaplegic (dpp). Here we show that a Dpp-activated Smad protein, phosphorylated Mad, is colocalized in eve-expressing cells during an extended developmental period. We demonstrate further that a mesodermally active enhancer of eve contains several Smad and Tin binding sites that are essential for enhancer activity in vivo. This enhancer also contains a number of binding sites for the Wg-effector Pangolin (Pan/Lef-1), which are required for full levels of enhancer activity. However, we find that their main function is to prevent ectopic enhancer activity in the dorsal mesoderm. This suggests that, in the absence of Wg signaling, Pan binding serves to abrogate the synergistic activities of Smads and Tin in eve activation while, in cells that receive Wg signals, Pan is converted into a coactivator that promotes eve induction. Together, these data show that the eve enhancer integrates several regulatory pathways via the combinatorial binding of the mesoderm-intrinsic regulator Tin and the effectors of the Dpp and Wg signals.

Animals↗

PubMed2000

Signaling pathways to the assembly of an interferon-beta enhanceosome. Chemical genetic studies with a small molecule.

Small molecules that modulate specific protein functions are valuable tools for dissecting complex signaling pathways. Here, we identified a small molecule that induces the assembly of the interferon-beta (IFN-beta) enhanceosome by stimulating all the enhancer-binding activator proteins: ATF2/c-JUN, IRF3, and p50/p65 of NF-kappaB. This compound stimulates mitogen-activated protein kinase kinase kinase 1 (MEKK1), which is a member of a family of proteins involved in stress-mediated signaling pathways. Consistent with this, MEKK1 activates IRF3 in addition to ATF2/c-JUN and NF-kappaB for the assembly of the IFN-beta enhanceosome. MEKK1 activates IRF3 through the c-JUN amino-terminal kinase (JNK) pathway but not the p38 and IkappaB kinase (IKK) pathway. Taken together with previous observations, these results implicate that, for the assembly of an IFN-beta enhanceosome, MEKK1 can induce IRF3 and ATF2/c-JUN through the JNK pathway, whereas it can induce NF-kappaB through the IKK pathway. Thus, specific MEKK family proteins may be able to integrate some of multiple signal transduction pathways leading to the specific activation of the IFN-beta enhanceosome.

Enhancer Elements, Genetic↗

PubMed2002

Clinical relevance of the TNF-alpha promoter/enhancer polymorphism in patients with aplastic anemia.

Immune-mediated inhibition of hematopoiesis has been suspected as a major cause of the suppressed growth of progenitor cells in aplastic anemia (AA). Overproduction of TNF-alpha by bone marrow and peripheral blood-derived cells was shown to be of pathogenetic importance. Genetic factors have been suggested by higher specific histocompatibility antigen frequencies among AA patients as a group and among those unresponsive to immunosuppressive therapy with cyclosporine. In the present work we expand on the evidence for the contribution of the TNF system to therapeutic responses in patients with AA. The response to immunosuppressive therapy at 3 months was found to be significantly more frequent among carriers of the TNF2 (TNF -308 A) gene (TNF2 homozygotes and heterozygotes of the TNF-alpha promoter/enhancer polymorphism) than among those patients not carrying the TNF2 gene. The allelic distribution of the LT-alpha (TNF-beta) NcoI and IL-1 receptor antagonist variable number tandem repeat (VNTR) polymorphisms did not differ among the subgroups of patients. The association of the TNF-alpha genotype with a response to immunosuppressive therapy points to an immunogenetic association that may contribute to the pathogenesis and therapeutic response of aplastic anemia.

Adolescent↗

PubMed2007

Wingless directly represses DPP morphogen expression via an armadillo/TCF/Brinker complex.

BACKGROUND: Spatially restricted morphogen expression drives many patterning and regeneration processes, but how is the pattern of morphogen expression established and maintained? Patterning of Drosophila leg imaginal discs requires expression of the DPP morphogen dorsally and the wingless (WG) morphogen ventrally. We have shown that these mutually exclusive patterns of expression are controlled by a self-organizing system of feedback loops that involve WG and DPP, but whether the feedback is direct or indirect is not known. METHODS/FINDINGS: By analyzing expression patterns of regulatory DNA driving reporter genes in different genetic backgrounds, we identify a key component of this system by showing that WG directly represses transcription of the dpp gene in the ventral leg disc. Repression of dpp requires a tri-partite complex of the WG mediators armadillo (ARM) and dTCF, and the co-repressor Brinker, (BRK), wherein ARM.dTCF and BRK bind to independent sites within the dpp locus. CONCLUSIONS/SIGNIFICANCE: Many examples of dTCF repression in the absence of WNT signaling have been described, but few examples of signal-driven repression requiring both ARM and dTCF binding have been reported. Thus, our findings represent a new mode of WG mediated repression and demonstrate that direct regulation between morphogen signaling pathways can contribute to a robust self-organizing system capable of dynamically maintaining territories of morphogen expression.

Animals↗

PubMed1985

Genetic and physical studies of a portion of the white locus participating in transcriptional regulation and in synapsis-dependent interactions in Drosophila adult tissues.

We have identified and sequenced the portion of the white locus affected by an idiosyncratic set of white mutant alleles (the wsp alleles). The affected white locus portion (wsp region) extends from ca. 590 base pairs (bp) to ca. 1270 bp 5' to the apparent start site for the major white transcription unit. Based on the properties of these mutant alleles, we infer the existence of two distinct cis-acting regulatory elements in the wsp region and a third element mapping 3' to this region (3' to position ca. -670). Our analysis allows us to define the apparent position of one of the two wsp region elements with substantial precision. Examination of the DNA sequences in this region suggests that it is functionally similar to the enhancers identified in vertebrates. This same element participates in synapsis-dependent genetic interactions, suggesting a largely unexpected relationship between enhancer-like, cis-acting genetic elements and the genetic elements responsible for the synapsis-dependent genetic interactions in trans revealed by the existence of transvection effects. Our results further suggest that a presumptive regulatory locus (suppressor-of-white-spotted) regulates white transcription in adult tissues and is not involved in regulating white expression in larvae. We discuss the regulation of white expression in light of our studies. We also demonstrate unusual structures for an X-ray-induced deletion and a spontaneous deletion.

Alleles↗

PubMed1990

Differential regulation of human immunodeficiency viruses (HIVs): a specific regulatory element in HIV-2 responds to stimulation of the T-cell antigen receptor.

The human immunodeficiency viruses (HIVs) types 1 and 2 have similar genetic organization but differ significantly in nucleic acid sequence. Although infection by either agent leads to symptoms of immunodeficiency, recent studies suggest potential differences in the time course and severity of these diseases. In this report, the transcriptional regulation and induction of these retroviruses were analyzed. We report that the regulation of HIV-2 differs from that of HIV-1: a distinct T-cell activation pathway, triggering of the CD3 component of the T-cell receptor complex, stimulates HIV-2 but not HIV-1 gene expression. The response to T-cell receptor stimulation in HIV-2 is mediated partly by an upstream regulatory element, termed CD3R, which is recognized by a sequence-specific DNA binding protein, NF-CD3R. Jurkat T leukemia cell lines containing HIV-2 provirus also showed increased viral replication after stimulation of the T-cell receptor complex, in contrast to HIV-1. These findings suggest that transcriptional regulation and induction of HIV-2 differ from HIV-1 and raise the possibility that different cofactors contribute to the activation of HIV-1- and HIV-2-associated AIDS.

Antigens, CD↗

PubMed1997

Dominant enhancers of Egfr in Drosophila melanogaster: genetic links between the Notch and Egfr signaling pathways.

The Drosophila epidermal growth factor receptor (EGFR) is a key component of a complex signaling pathway that participates in multiple developmental processes. We have performed an F1 screen for mutations that cause dominant enhancement of wing vein phenotypes associated with mutations in Egfr. With this screen, we have recovered mutations in Hairless (H), vein, groucho (gro), and three apparently novel loci. All of the E(Egfr)s we have identified show dominant interactions in transheterozygous combinations with each other and with alleles of N or Su(H), suggesting that they are involved in cross-talk between the N and EGFR signaling pathways. Further examination of the phenotypic interactions between Egfr, H, and gro revealed that reductions in Egfr activity enhanced both the bristle loss associated with H mutations, and the bristle hyperplasia and ocellar hypertrophy associated with gro mutations. Double mutant combinations of Egfr and gro hypomorphic alleles led to the formation of ectopic compound eyes in a dosage sensitive manner. Our findings suggest that these E(Egfr)s represent links between the Egfr and Notch signaling pathways, and that Egfr activity can either promote or suppress Notch signaling, depending on its developmental context.

Animals↗

PubMed2003

Regulation of alternative splicing of Gtf2ird1 and its impact on slow muscle promoter activity.

A human MusTRD (muscle TFII-I repeat domain (RD)-containing protein) isoform was originally identified in a yeast one-hybrid screen as a protein that binds the slow fibre-specific enhancer of the muscle gene troponin I slow [O'Mahoney, Guven, Lin, Joya, Robinson, Wade and Hardeman (1998) Mol. Cell. Biol. 18, 6641-6652]. MusTRD shares homology with the general transcription factor TFII-I by the presence of diagnostic I-RDs [Roy (2001) Gene 274, 1-13]. The human gene encoding MusTRD, GTF2IRD1 ( WBSCR11 / GTF3 ), was subsequently located on chromosome 7q11.23, a region deleted in the neurodegenerative disease, Williams-Beuren Syndrome [Osborne, Campbell, Daradich, Scherer, Tsui, Franke, Peoples, Francke, Voit, Kramer et al. (1999) Genomics 57, 279-284; Franke, Peoples and Francke (1999) Cytogenet. Cell. Genet. 86, 296-304; Tassabehji, Carette, Wilmot, Donnai, Read and Metcalfe (1999) Eur. J. Hum. Genet. 7, 737-747]. The haploinsufficiency of MusTRD has been implicated in the myopathic aspect of this disease, which manifests itself in symptoms such as lowered resistance to fatigue, kyphoscoliosis, an abnormal gait and joint contractures [Tassabehji, Carette, Wilmot, Donnai, Read and Metcalfe (1999) Eur. J. Hum. Genet. 7, 737-747]. Here, we report the identification of 11 isoforms of MusTRD in mouse skeletal muscles. These isoforms were isolated from a mouse skeletal muscle cDNA library and reverse transcription-PCR on RNA from various adult and embryonic muscles. The variability in these isoforms arises from alternative splicing of a combination of four cassettes and two mutually exclusive exons, all in the 3' region of the primary transcript of Gtf2ird1, the homologous mouse gene. The expression of some of these isoforms is differentially regulated spatially, suggesting individual regulation of the expression of these isoforms. Co-transfection studies in C2C12 muscle cell cultures reveal that isoforms differentially regulate muscle fibre-type-specific promoters. This indicates that the presence of different domains of MusTRD influences the activity exerted by this molecule on multiple promoters active in skeletal muscle.

Alternative Splicing↗

PubMed1997

The vrille gene of Drosophila is a maternal enhancer of decapentaplegic and encodes a new member of the bZIP family of transcription factors.

We report here the genetical and molecular characterization of a new Drosophila zygotic lethal locus, vrille (vri). Vri alleles act not only as dominant maternal enhancers of embryonic dorsoventral patterning defects caused by easter and decapentaplegic (dpp) mutations, but also as dominant zygotic enhancers of dpp alleles for phenotypes in wing. The vri gene encodes a new member of the bZIP family of transcription factors closely related to gene 9 of Xenopus laevis, induced by thyroid hormone during the tadpole tail resorption program, and NF-IL3A, a human T cell transcription factor that transactivates the interleukin-3 promoter. NF-IL3A shares 93% similarity and 60% identity with Vri for a stretch of 68 amino acids that includes the bZIP domain. Although all the alleles tested behave like antimorphs, the dominant enhancement is also seen with a nonsense mutation allele that prevents translation of the bZIP domain. Because of the strong domainant enhancement of dpp phenotypes by vri alleles in both embryo and wing, and also the similarity between the wing vein phenotypes caused by the vri and shortvein dpp alleles, we postulate that vri interacts either directly or indirectly with certain components of the dpp (a TGF beta homologue) signal transduction pathway.

Alleles↗

PubMed2005

Herpes simplex virus amplicon delivery of a hypoxia-inducible soluble vascular endothelial growth factor receptor (sFlk-1) inhibits angiogenesis and tumor growth in pancreatic adenocarcinoma.

BACKGROUND: Tumor hypoxia induces vascular endothelial growth factor (VEGF) expression, which stimulates angiogenesis and tumor proliferation. The VEGF signaling pathway is inhibited by soluble VEGF receptors (soluble fetal liver kinase 1; sFlk-1), which bind VEGF and block its interaction with endothelial cells. Herpes simplex virus (HSV) amplicons are replication-incompetent viruses used for gene delivery. We attempted to attenuate angiogenesis and inhibit pancreatic tumor growth through HSV amplicon-mediated expression of sFlk-1 under hypoxic control. METHODS: A multimerized hypoxia-responsive enhancer (10 x HRE) was cloned upstream of the sFlk-1 gene (10 x HRE/sFlk-1). A novel HSV amplicon expressing 10 x HRE/sFlk-1 was genetically engineered (HSV10 x HRE/sFlk-1).Human pancreatic adenocarcinoma cells (AsPC1) were transduced with HSV10 x HRE/sFlk-1 and incubated in normoxia (21% oxygen) or hypoxia (1% oxygen). Capillary inhibition was evaluated by human umbilical vein endothelial cell assay. Western blot assessed sFlk-1 expression. AsPC1 flank tumor xenografts (n = 24) were transduced with HSV10 x HRE/sFlk-1. RESULTS: Media from normoxic AsPC1 transduced with HSV10 x HRE/sFlk-1 yielded a 36% reduction in capillary formation versus controls (P < .05), whereas hypoxic AsPC1 yielded a 76% reduction (P < .005). Western blot of AsPC1 transduced with HSV10 x HRE/sFlk-1 demonstrated greater sFlk-1 expression in hypoxia versus normoxia. AsPC1 flank tumors treated with HSV10 x HRE/sFlk-1 exhibited a 59% reduction in volume versus controls (P < .000001). CONCLUSIONS: HSV amplicon delivery of a hypoxia-inducible soluble VEGF receptor significantly reduces new vessel formation and tumor growth. Tumor hypoxia can thus be used to direct antiangiogenic therapy to pancreatic adenocarcinoma.

Adenocarcinoma↗

PubMed1987

High efficiency gene transfer and expression in normal murine B lymphocytes.

The introduction of new genetic information into hematopoietic cells offers a new approach for investigating the molecular events controlling differentiation. Retrovirus vectors have been used to transfer new genes with high efficiency into murine hematopoietic cells, primarily of the myeloid lineage. In this report, we show that vectors carrying the dominant, selectable gene for neomycin resistance (neo gene) can successfully infect normal murine B lymphocytes (CFU-B). The infected CFU-B formed colonies in vitro in high concentrations (750 micrograms/ml) of G418, a neomycin analogue. That B lymphocytes contained the neo gene was confirmed by the findings that the putative B cell colonies growing in G418 contained antibody-producing cells and that the cells responding to the B cell mitogen, LPS, were resistant to G418. Infection of normal spleen cells with different vectors containing a variety of transcriptional regulatory sequences resulted in 7-40% of the CFU-B becoming G418 resistant. Introduction of the immunoglobulin heavy chain enhancer into NEO vectors appeared to augment the expression of the neo gene, since the level of G418 resistance was higher in B cells infected with a NEO vector containing the enhancer than in cells infected with a vector lacking the enhancer.

Animals↗