Sequences required for induction of neurotensin receptor gene expression during neuronal differentiation of N1E-115 neuroblastoma cells

Molecular Imaging of Stem Cells

Regenerative medicine with the use of stem cells has appeared as a potential therapeutic alternative for many disease states. Despite initial enthusiasm, there has been relatively slow transition to clinical trials. In large part, numerous questions remain regarding the viability, biology and efficacy of transplanted stem cells in the living subject. The critical issues highlighted the importance of developing tools to assess these questions. Advances in molecular biology and imaging have allowed the successful non-invasive monitoring of transplanted stem cells in the living subject. Over the years these methodologies have been updated to assess not only the viability but also the biology of transplanted stem cells. In this review, different imaging strategies to study the viability and biology of transplanted stem cells are presented. Use of these strategies will be critical as the different regenerative therapies are being tested for clinical use.

Transcriptional regulation of pro-apoptotic protein kinase Cdelta: implications for oxidative stress-induced neuronal cell death

We previously demonstrated that protein kinase Cδ (PKCδ; PKC delta) is an oxidative stress-sensitive kinase that plays a causal role in apoptotic cell death in neuronal cells. Although PKCδ activation has been extensively studied, relatively little is known about the molecular mechanisms controlling PKCδ expression. To characterize the regulation of PKCδ expression, we cloned an ∼2-kbp 5'-promoter segment of the mouse Prkcd gene. Deletion analysis indicated that the noncoding exon 1 region contained multiple Sp sites, including four GC boxes and one CACCC box, which directed the highest levels of transcription in neuronal cells. In addition, an upstream regulatory region containing adjacent repressive and anti-repressive elements with opposing regulatory activities was identified within the region -712 to -560. Detailed mutagenesis studies revealed that each Sp site made a positive contribution to PKCδ promoter expression. Overexpression of Sp family proteins markedly stimulated PKCδ promoter activity without any synergistic transactivating effect. Furthermore, experiments in Sp-deficient SL2 cells indicated long isoform Sp3 as the essential activator of PKCδ transcription. Importantly, both PKCδ promoter activity and endogenous PKCδ expression in NIE115 cells and primary striatal cultures were inhibited by mithramycin A. The results from chromatin immunoprecipitation and gel shift assays further confirmed the functional binding of Sp proteins to the PKCδ promoter. Additionally, we demonstrated that overexpression of p300 or CREB-binding protein increases the PKCδ promoter activity. This stimulatory effect requires intact Sp-binding sites and is independent of p300 histone acetyltransferase activity. Finally, modulation of Sp transcriptional activity or protein level profoundly altered the cell death induced by oxidative insult, demonstrating the functional significance of Sp-dependent PKCδ gene expression. Collectively, our findings may have implications for development of new translational strategies against oxidative damage.

Structure and regulation of the mDot1 gene, a mouse histone H3 methyltransferase

The nucleotide sequence data reported have been deposited in the DDBJ, EMBL, GenBank(R) and GSDB Nucleotide Sequence Databases under accession numbers AY196089, AY196090, AY376663, AY377920 and AY376664. Recently, a new class of histone methyltransferases that plays an indirect role in chromatin silencing by targeting a conserved lysine residue in the nucleosome core was described, namely the Dot1 (disruptor of telomeric silencing) family [Feng, Wang, Ng, Erdjument-Bromage, Tempst, Struhl and Zhang (2002) Curr. Biol. 12, 1052-1058; van Leeuwen, Gafken and Gottschling (2002) Cell (Cambridge, Mass.) 109, 745-756; Ng, Feng, Wang, Erdjument-Bromage, Tempst, Zhang and Struhl (2002) Genes Dev. 16, 1518-1527]. In the present study, we report the isolation, genomic organization and in vivo expression of a mouse Dot1 homologue (mDot1). Expressed sequence tag analysis identified five mDot1 mRNAs (mDot1a-mDot1e) derived from alternative splicing. mDot1a and mDot1b encode 1540 and 1114 amino acids respectively, whereas mDot1c-mDot1e are incomplete at the 5'-end. mDot1a is closest to its human counterpart (hDot1L), sharing 84% amino acid identity. mDot1b is truncated at its N- and C-termini and contains an internal deletion. The five mDot1 isoforms are encoded by 28 exons on chromosome 10qC1, with exons 24 and 28 further divided into two and four sections respectively. Alternative splicing occurs in exons 3, 4, 12, 24, 27 and 28. Northern-blot analysis with probes corresponding to the methyltransferase domain or the mDot1a-coding region detected 7.6 and 9.5 kb transcripts in multiple tissues, but only the 7.6 kb transcript was evident in mIMCD3-collecting duct cells. Transfection of mDot1a-EGFP constructs (where EGFP stands for enhanced green fluorescent protein) into human embryonic kidney (HEK)-293T or mIMCD3 cells increased the methylation of H3-K79 but not H3-K4, -K9 or -K36. Furthermore, DMSO induced mDot1 gene expression and methylation specifically at H3-K79 in mIMCD3 cells in a time- and dose-dependent manner. Collectively, these results add new members to the Dot1 family and show that mDot1 is involved in a DMSO-mediated signal-transduction pathway in collecting duct cells.

CYP1B1 gene in endometrial cancer

Metabolic activation of estradiol has been shown to be a key factor in endometrial carcinogenesis. 4-hydroxy estrogens (CYP1B1 metabolites) received particular attention because of their causative role in malignant transformation of various organs including endometrium. CYP1B1 displays the highest level of expression in endometrium. 4-hydroxy estrogens can bind to DNA via their quinone metabolites and cause oxidative damage in endometrial cancer. Moreover, the 4-hydroxy estrogens bind to the estrogen receptor and have estrogenic effects on target tissues. Six polymorphisms of the CYP1B1 gene have been described of which four result in amino acid substitutions; 1-13C-->T, codon 48C-->G, codon 119G-->T, codon 432C-->G, codon 449T-->C and codon 453A-->G. The polymorphisms on exons 2 and 3 have significant effects on the catalytic function of CYP1B1. Polymorphisms on specific regions of CYP1B1 gene result in hyperactivation of the protein and can lead to a higher susceptibility in the incidence of various cancers. Thus, inherited alterations in CYP1B1 hydroxylation activity may be associated with significant changes in estrogen metabolism and, thereby, may possibly explain inter-individual differences in endometrial cancer risk associated with estrogen-mediated carcinogenesis.

Roles of Ets proteins, NF-kappa B and nocodazole in regulating induction of transcription of mouse germline Ig alpha RNA by transforming growth factor-beta 1

Antibody class switch recombination (CSR) occurs after antigen activation of B cells. CSR is directed to specific heavy chain isotypes by cytokines and B cell activators that induce transcription from the unrearranged, or germline (GL), C(H) region genes. Transforming growth factor (TGF)-beta1 is essential for switch recombination to IgA due to its ability to induce transcription from GL Ig alpha genes. It has been shown that the promoters which regulate transcription of mouse and human GL alpha RNAs contain a TGF-beta1-responsive element that binds Smad and core binding factor (CBFalpha)/AML/PEBPalpha/RUNX: They also contain other elements which bind the transcription factors CREB, BSAP and Ets family proteins. In this manuscript we demonstrate that two tandem Ets sites in the mouse GL alpha promoter bind the transcription factors Elf-1 and PU.1, and that the 3' site is essential for expression of a luciferase reporter gene driven by the GL alpha promoter. Binding of Elf-1 to the GL alpha promoter is inducible by lipopolysaccharide in nuclear extracts from splenic B cells. An NF-kappaB site is identified, although it does not contribute to expression of the promoter in reporter gene assays. Since CSR to IgA is greatly reduced in NF-kappaB/p50-deficient mice, these data support the hypothesis that NF-kappaB has roles in switching in addition to regulation of GL transcription. Finally, we demonstrate that nocodazole, which disrupts microtubules that sequester Smad proteins in the cytoplasm, stimulates transcription from the GL alpha promoter.

Neuroblastoma cell lines--a versatile in vitro model in neurobiology

Neuroblastoma (NB) cell lines are transformed, neural crest derived cells, capable of unlimited proliferation in vitro. These cell lines retain the ability of differentiation into neuronal cell types on treatment with various agents. This ability of NB cells to proliferate as well as to differentiate makes it an excellent in vitro system for various studies. This review article focuses on the applications and potential uses of murine and human NB cell lines. NB cells are extensively used for testing neurotoxicity of putative drugs such as antimalarial or anticancer agents. NB cell lines have wide applications in virus research to understand various aspects of virus-host cell interactions at the molecular and cellular levels. They have been used to dissect the relationships between proliferation, differentiation and apoptosis. This feature has been useful in understanding the pediatric cancer--neuroblastoma and for development of newer therapies.

Differential regulation of mouse germline Ig gamma 1 and epsilon promoters by IL-4 and CD40

Before Ig class switching, RNA transcription through the specific S regions undergoing recombination is induced by cytokines and other activators that induce and direct switching. The resulting germline (GL) transcripts are essential for switch recombination. To understand the differential regulation of mouse IgG1 and IgE, we compared the promoters for GL gamma1 and epsilon transcripts. We addressed the question of why the promoter that regulates GL epsilon transcription is more responsive to IL-4 than the gamma1 promoter and also why GL epsilon transcription is more dependent on IL-4 than is gamma1 transcription. We found that the IL-4-responsive region of the GL epsilon promoter is more inducible than that of the gamma1 promoter, although each promoter contains a binding site for the IL-4-inducible transcription factor Stat6, located immediately adjacent to a binding site for a basic region leucine zipper (bZip) family protein. However, the arrangement and sequences of the sites differ between the epsilon and gamma1 promoters. The GL epsilon promoter binds Stat6 with a 10-fold higher affinity than does the gamma1 promoter. Furthermore, the bZip elements of the two promoters bind different transcription factors, as the GL epsilon promoter binds and is activated by AP-1, whereas the gamma1 promoter binds and is activated by activating transcription factor 2. C/EBPbeta and C/EBPgamma also bind the gamma1 bZip element, although they inhibit rather than activate transcription. However, inhibition of promoter activity by C/EBPbeta does not require the bZip element and may instead occur via inhibiting the activity of NF-kappaB.

Evidence for class-specific factors in immunoglobulin isotype switching

Immunoglobulin class switch recombination (SR) occurs by a B cell-specific, intrachromosomal deletional process between switch regions. We have developed a plasmid-based transient transfection assay for SR to test for the presence of transacting switch activities. The plasmids are novel in that they lack a eukaryotic origin of DNA replication. The recombination activity of these switch substrates is restricted to a subset of B cell lines that support isotype switching on their endogenous loci and to mitogen-activated normal splenic B cells. The factors required for extrachromosomal plasmid recombination are constitutively expressed in proliferating splenic B cells and in B cell lines capable of inducibly undergoing immunoglobulin SR on their chromosomal genes. These studies suggest that mitogens that induce switching on the chromosome induce accessibility rather than switch recombinase activity. Finally, we provide evidence for two distinct switching activities which independently mediate mu-->alpha and mu-->gamma3 SR.