Purification and cloning of type A/B hnRNP proteins involved in transcriptional activation from the Rat spi 2 gene GAGA box

HNRNPAB-regulated lncRNA-ELF209 inhibits the malignancy of hepatocellular carcinoma

Our previous study demonstrated that heterogeneous nuclear ribonucleoprotein AB (HNRNPAB) is a key gene that facilitates metastasis of hepatocellular carcinoma (HCC). However, the molecular mechanisms behind this relationship are not fully understood. In our study, we utilized long-noncoding RNA (lncRNA) microarrays to identify a HNRNPAB-regulated lncRNA named lnc-ELF209. Our findings from chromatin immunoprecipitation assays indicate that HNRNPAB represses lnc-ELF209 transcription by directly binding to its promoter region. We also analyzed clinical samples from HCC patients and cell lines with quantitative real-time polymerase chain reactions, RNA in situ hybridization and immunohistochemistry, and found that there is a negative relationship between HNRNPAB and lnc-ELF209 expression. Up/downregulation assays and rescue assays indicate that lnc-ELF209 inhibits cell migration, invasion and epithelial-mesenchymal transition regulated by HNRNPAB. This suggests a new regulatory mechanism for HNRNPAB-promoted HCC progression. RNA pull-down and LC-MS/MS were used to determine triosephosphate isomerase, heat shock protein 90-beta and vimentin may be involved in the tumor-suppressed function of lnc-ELF209. Furthermore, we found lnc-ELF209 could stabilize TPI protein expression. We also found that lnc-ELF209 overexpression in HCCLM3 cell resulted in a lower rate of lung metastatic, which suggested a less aggressive HCC phenotype. Collectively, these findings offer new insights into the regulatory mechanisms that underlie HNRNPAB cancer-promoting activities and demonstrate that lnc-ELF209 is a HNRNPAB-regulated lncRNA that may play an important role in the inhibition of HCC progression.

Hnrnpab regulates neural cell motility through transcription of Eps8

Cell migration requires a complicated network of structural and regulatory proteins. Changes in cellular motility can impact migration as a result of cell-type or developmental stage regulated expression of critical motility genes. Hnrnpab is a conserved RNA-binding protein found as two isoforms produced by alternative splicing. Its expression is enriched in the subventricular zone (SVZ) and the rostral migratory stream within the brain, suggesting possible support of the migration of neural progenitor cells in this region. Here we show that the migration of cells from the SVZ of developing Hnrnpab^-/- mouse brains is impaired. An RNA-seq analysis to identify Hnrnpab-dependent cell motility genes led us to Eps8, and in agreement with the change in cell motility, we show that Eps8 is decreased in Hnrnpab^-/- SVZ tissue. We scrutinized the motility of Hnrnpab^-/- cells and confirmed that the decreases in both cell motility and Eps8 are restored by ectopically coexpressing both alternatively spliced Hnrnpab isoforms, therefore these variants are surprisingly nonredundant for cell motility. Our results support a model where both Hnrnpab isoforms work in concert to regulate Eps8 transcription in the mouse SVZ to promote the normal migration of neural cells during CNS development.

Viral DNA Replication Orientation and hnRNPs Regulate Transcription of the Human Papillomavirus 18 Late Promoter

The life cycle of human papillomaviruses (HPVs) is tightly linked to keratinocyte differentiation. Although expression of viral early genes is initiated immediately upon virus infection of undifferentiated basal cells, viral DNA amplification and late gene expression occur only in the mid to upper strata of the keratinocytes undergoing terminal differentiation. In this report, we show that the relative activity of HPV18 TATA-less late promoter P₈₁₁ depends on its orientation relative to that of the origin (Ori) of viral DNA replication and is sensitive to the eukaryotic DNA polymerase inhibitor aphidicolin. Additionally, transfected 70-nucleotide (nt)-long single-strand DNA oligonucleotides that are homologous to the region near Ori induce late promoter activity. We also found that promoter activation in raft cultures leads to production of the late promoter-associated, sense-strand transcription initiation RNAs (tiRNAs) and splice-site small RNAs (spliRNAs). Finally, a cis-acting AAGTATGCA core element that functions as a repressor to the promoter was identified. This element interacts with hnRNP D0B and hnRNP A/B factors. Point mutations in the core prevented binding of hnRNPs and increased the promoter activity. Confirming this result, knocking down the expression of both hnRNPs in keratinocytes led to increased promoter activity. Taking the data together, our study revealed the mechanism of how the HPV18 late promoter is regulated by DNA replication and host factors.

It has been known for decades that the activity of viral late promoters is associated with viral DNA replication among almost all DNA viruses. However, the mechanism of how DNA replication activates the viral late promoter and what components of the replication machinery are involved remain largely unknown. In this study, we characterized the P₈₁₁ promoter region of HPV18 and demonstrated that its activation depends on the orientation of DNA replication. Using single-stranded oligonucleotides targeting the replication fork on either leading or lagging strands, we showed that viral lagging-strand replication activates the promoter. We also identified a transcriptional repressor element located upstream of the promoter transcription start site which interacts with cellular proteins hnRNP D0B and hnRNP A/B and modulates the late promoter activity. This is the first report on how DNA replication activates a viral late promoter.

The activity of the carbamoyl phosphate synthase 1 promoter in human liver-derived cells is dependent on hepatocyte nuclear factor 3-beta

Carbamoyl phosphate synthase 1 (CPS1) is the rate‐limiting enzyme in the first step of the urea cycle and an indispensable enzyme in the metabolism of human liver. However, CPS1 epigenetic regulation involves promoter analysis and the role of liver‐enriched transcription factors (LETFs), which is not fully elucidated. In this work, the promoter region of hCPS1 gene was cloned, and its activity was investigated. An LETF, hepatocyte nuclear factor 3‐beta (HNF3β), was found to promote the transcriptional expression of CPS1 in liver‐derived cell lines. In addition, dual‐luciferase reporter assay shows that the essential binding sites of the HNF3β may exist in the oligonucleotide −70 nt to +73 nt. Two putative binding sites are available for HNF3β. Mutation analysis results show that the binding site 2 of HNF3β was effective, and the transcriptional activity of CPS1 promoter significantly decreased after mutation. Electrophoretic mobile shift assay (EMSA) and ChIP assay confirmed that HNF3β can interact with the binding site in the CPS1 promoter region of −70 nt to +73 nt promoter region in vivo and in vitro to regulate the transcription of CPS1. Moreover, HNF3β overexpression enhanced the transcription of CPS1 and consequently improved the mRNA and protein levels of CPS1, whereas the knockdown of HNF3β showed the opposite effects. Finally, urea production in cells was measured, and ammonia detoxification improved significantly in cells after transfection with HNF3β. HNF3β plays a vital role in regulation of CPS1 gene and could promote the metabolism of ammonia by regulating CPS1 expression.

HNRNPAB induces epithelial-mesenchymal transition and promotes metastasis of hepatocellular carcinoma by transcriptionally activating SNAIL

Expression of heterogeneous nuclear ribonucleoprotein AB (HNRNPAB) has been reported to be dysregulated in tumors, but its specific contributions to tumor formation and progression are not fully understood. Here, we demonstrate that HNRNPAB is overexpressed in highly metastatic cells and tumor tissues from patients with hepatocellular carcinoma (HCC) with recurrence. We found that HNRNPAB overexpression promoted epithelial-mesenchymal transition (EMT) in a manner associated with HCC metastasis in vitro and in vivo. RNA interference-mediated silencing of the EMT factor SNAIL attenuated HNRNPAB-enhanced cell invasion in vitro and lung metastasis in vivo. Mechanistically, HNRNPAB acted to transactivate SNAIL1 transcription, which in turn inhibited transcription of the pivotal SNAIL target gene E-cadherin. Overexpression of HNRNPAB in HCC samples correlated with higher SNAIL levels, shorter overall survival, and higher tumor recurrence. HNRNPAB overexpression, alone or in combination with SNAIL, was found to be a significant independent risk factor for recurrence and survival after curative resection. In conclusion, our findings define HNRNPAB as an activator of EMT and metastasis in HCC that predicts poor clinical outcomes.

Functional impact of heterogeneous nuclear ribonucleoprotein A2/B1 in smooth muscle differentiation from stem cells and embryonic arteriogenesis

Heterogeneous nuclear ribonucleoproteins (hnRNPs) play various roles in transcriptional and post-transcriptional modulation of gene expression. However, it remains unclear if hnRNPs are associated with smooth muscle cell (SMC) differentiation from stem cells and embryonic arteriogenesis. In this study, mouse embryonic stem (ES) cells were cultivated on collagen IV-coated plates and smooth muscle differentiation medium. We found that hnRNPA2/B1 gene and protein expression was significantly up-regulated following 3-7 days of cell differentiation. hnRNPA2/B1 knockdown resulted in down-regulation of specific smooth muscle markers and transcription factors, whereas enforced expression of hnRNPA2/B1 enhanced the expression of these genes. Moreover, we demonstrated by using luciferase and chromatin immunoprecipitation assays that hnRNPA2/B1 could transcriptionally regulate SMC gene expression through direct binding to promoters of Smαa and Sm22α genes. We further demonstrated that chromobox protein homolog gene 3, a previously identified SMC differentiation regulatory nuclear protein, is required for hnRNPA2/B1-mediated SMC differentiation gene expression. Importantly, specifically designed Hnrnpa2/b1 morpholinos for in vivo knockdown could inhibit the migration and differentiation of neural crest cells into SMCs in chick embryos. This resulted in the maldevelopment of branchial arch arteries and increased embryo lethality at a later developmental stage. Our findings demonstrated that hnRNPA2/B1 plays a functional role in SMC differentiation from stem cells in vitro and embryonic branchial arch artery development. This indicates that hnRNPA2/B1 is a potential modulating target for deriving SMCs from stem cells and cardiovascular regenerative medicine.

Human growth hormone receptor gene expression is regulated by Gfi-1/1b and GAGA cis-elements

Human growth hormone receptor (hGHR) gene regulation is complex: mRNAs are transcribed from multiple variant (V) 5'UTR exons, several ubiquitously while others only in the postnatal hepatocyte. The liver-specific V1 exon promoter contains Gfi-1/1b repressor sites adjacent to a GAGA box, a GH response element (GHRE) in several mammalian genes. GAGA boxes are also present in the ubiquitously expressing V3 exon promoter. Heterologous sites in bovine, ovine and murine GHR genes suggest conserved roles. GAGA factor stimulated V1 and V3 promoters while Gfi-1/1b repressed basal and GAF-stimulated V1 transcription. HGH treatment of HepG2 cells resulted in a new complex forming with V3 GAGA elements, suggesting a functional GHRE. Data suggest liver-specific V1 transcription is regulated by inhibitory Gfi-1/1b and stimulatory GAGA cis-elements and Gfi-1/1b may control the lack of V1 expression in fetal liver, hepatic tumours and non-hepatic tissues. In addition, hGH may regulate hGHR expression through V3 GAGA boxes.

DcpS as a therapeutic target for spinal muscular atrophy

Spinal muscular atrophy (SMA) is caused by deletion or mutation of both copies of the SMN1 gene, which produces an essential protein known as SMN. The severity of SMA is modified by variable copy number of a second gene,SMN2, which produces an mRNA that is incorrectly spliced with deletion of the last exon. We described previously the discovery of potent C5-substituted quinazolines that increase SMN2 gene expression by 2-fold. Discovery of potent SMN2 promoter inducers relied on a cellular assay without knowledge of the molecular target. Using protein microarray scanning with a radiolabeled C5-substituted quinazoline probe, we identified the scavenger decapping enzyme, DcpS, as a potential binder. We show that the C5-substituted quinazolines potently inhibit DcpS decapping activity and that the potency of inhibition correlates with potency forSMN2 promoter induction. Binding of C5-substituted quinazolines to DcpS holds the enzyme in an open, catalytically incompetent conformation. DcpS is a nuclear shuttling protein that binds and hydrolyzes the m(7)GpppN mRNA cap structure and a modulator of RNA metabolism. Therefore DcpS represents a novel therapeutic target for modulating gene expression by a small molecule.

Cloning and characterization of porcine CArG binding factor A expression in the anterior pituitary

CArG binding factor A (CBF-A) is a transcription factor first isolated from mouse C2 myogenic cells. Several lines of evidence indicate that CBF-A is also present in the anterior pituitary lobe and participates in the process of development and cell transformation. This study was performed to clone porcine CBF-A and to investigate its roles in the porcine anterior pituitary lobe. The predicted amino acid sequence of porcine CBF-A showed a unique insertion of five TG-repeats in the N-terminal region in comparison with those of other mammals, whereas the other regions appeared to be mostly conserved including two RNA recognition motifs in the middle region. Investigation of the expression of CBF-A gene during porcine pituitary development by RT-PCR showed an exclusive and temporary decrease in expression level shortly after birth in both sexes that was gradually but insufficiently restored. The expression of fluorescence protein-fused CBF-A in CHO cells demonstrated that CBF-A is located in the nuclei. We examined whether CBF-A regulates the expression of pituitary hormone genes in CHO cells and found that CBF-A significantly stimulated the promoter activity of growth hormone and prolactin by about 2-fold but did not stimulate the LHbeta gene. The specific DNA binding ability of porcine CBF-A was examined using serial oligonucleotides, CArG box and CC(W)0-6GG (W=A or T). As a result, porcine CBF-A was shown to have a high binding affinity for double- and single-stranded CC(W)6GG but no affinity for the known sequences of the CBF-A-target genes. Accordingly, this study demonstrated that porcine CBF-A may play a role in regulating at least two pituitary hormone genes, GH and PRL.

In cultured oligodendrocytes the A/B-type hnRNP CBF-A accompanies MBP mRNA bound to mRNA trafficking sequences

Heterogeneous ribonucleoproteins (hnRNPs) have key roles in RNA biogenesis, including pre-mRNP assembly, transport and cytoplasmic localization. Here we show by biochemical fractionation of nuclear extracts and protein-protein interaction assays that the A/B-type hnRNP CBF-A is in a multiprotein complex with hnRNP A2 and A3 and hnRNP U. Using RNA affinity chromatography and gel retardation assays, CBF-A was found to bind directly to RNA trafficking sequences in the 3'-UTR of the myelin basic protein (MBP) mRNA. In primary oligodendrocytes, astrocytes, neurons, and mouse forebrain sections, CBF-A revealed a characteristic granular cytoplasmic distribution. In mouse forebrain CBF-A-positive granules were preferentially found in regions with loosely bundled myelin fibers. In cultured oligodendrocytes, CBF-A was found to be specifically associated with endogenous MBP mRNA and CBF-A gene silencing resulted in the retention of MBP granules in the cell body. Finally, immunoelectron microscopy in differentiating oligodendrocytes showed that CBF-A is located in cytoplasmic granules that are often associated with the cytoskeleton. The results suggest that CBF-A is a novel transacting factor required for cytoplasmic mRNA transport and localization.

Heterogeneous nuclear ribonucleoprotein A/B and G inhibits the transcription of gonadotropin-releasing-hormone 1

Gonadotropin-releasing hormone 1 (GnRH1) causes the release of gonadotropins from the pituitary to control reproduction. Here we report that two heterogeneous nuclear ribonucleoproteins (hnRNP-A/B and hnRNP-G) bind to the GnRH-I upstream promoter region in a cichlid fish Astatotilapia burtoni. We identified these binding proteins using a newly developed homology based method of mass spectrometric peptide mapping. We show that both hnRNP-A/B and hnRNP-G co-localize with GnRH1 in the pre-optic area of the hypothalamus in the brain. We also demonstrated that these ribonucleoproteins exhibit similar binding capacity in vivo, using immortalized mouse GT1-7 cells where overexpression of either hnRNP-A/B or hnRNP-G significantly down-regulates GnRH1 mRNA levels in GT1-7 cells, suggesting that both act as repressors in GnRH1 transcriptional regulation.

A proximal activator of transcription in epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is an important mechanism for phenotypic conversion in normal development and disease states such as tissue fibrosis and metastasis. While this conversion of epithelia is under tight transcriptional control, few of the key transcriptional proteins are known. Fibroblasts produced by EMT express a gene encoding fibroblast-specific protein 1 (FSP1), which is regulated by a proximal cis-acting promoter element called fibroblast transcription site-1 (FTS-1). In mass spectrometry, chromatin immunoprecipitation, and siRNA studies, we used FTS-1 as a unique probe for mediators of EMT and identified a complex of 2 proteins, CArG box-binding factor-A (CBF-A) and KRAB-associated protein 1 (KAP-1), that bind this site. Epithelial cells engineered to conditionally express recombinant CBF-A (rCBF-A) activate the transcription of FSP1 and undergo EMT. The FTS-1 response element also exists in the promoters modulating a broader EMT transcriptome, including Twist, and Snail, as well as E-cadherin, beta-catenin, ZO 1, vimentin, alpha1(I) collagen, and alpha-smooth muscle actin, and the induction of rCBF-A appropriately alters their expression as well. We believe formation of the CBF-A/KAP-1/FTS-1 complex is sufficient for the induction of FSP1 and a novel proximal activator of EMT.

CArG box-binding factor-A interacts with multiple motifs in immunoglobulin promoters and has a regulated subcellular distribution

CArG box-binding factor-A (CBF-A) is a protein involved in transcriptional control and interacts specifically with the penta-decameric (pd) element in kappa promoters. We show here that CBF-A will also bind specifically to a second region in the kappa promoter that overlaps with an early B cell factor binding site. Furthermore, the same region is present in multiple Ig promoters and we show that CBF-A can bind to several of these. Mitogenic stimulation of untransformed B lymphocytes promoted nuclear localisation of CBF-A. Using enhanced GFP (EGFP)-tagged constructs and transfection into COS7 cells, a nuclear localisation signal was defined in the C terminus of CBF-A. Deletion of only 13 amino acids from the C terminus of CBF-A led to the accumulation of the protein in bright speckles at the nuclear/cytoplasmic border. We also identified the heterogeneous ribonucleoprotein H as a specific interaction partner of CBF-A, but this interaction could be detected in the cytoplasm only. Thus, CBF-A has the potential to regulate the expression of multiple Ig V genes and has a complex, mitogen-responsive regulation of its intracellular localisation.

The role of proximal-enhancer elements in the glucocorticoid regulation of carbamoylphosphate synthetase gene transcription from the upstream response unit

As part of the urea cycle, carbamoylphosphate synthetase (CPS) converts toxic ammonia resulting from amino-acid catabolism into urea. Liver-specific and glucocorticoid-dependent expression of the gene involves a distal enhancer, a promoter-proximal enhancer, and the minimal promoter itself. When challenged with glucocorticoids, the glucocorticoid-responsive unit (GRU) in the distal enhancer of the carbamoylphosphate-synthetase gene can only activate gene expression if, in addition to the minimal promoter, the proximal enhancer is present. Here, we identify and characterise two elements in the proximal CPS enhancer that are involved in glucocorticoid-dependent gene activation mediated by the GRU. A purine-rich stretch forming a so-called GAGA-box and a glucocorticoid-response element (GRE) are both crucial for the efficacy of the GRU and appear to constitute a promoter-proximal response unit that activates the promoter. The glucocorticoid response of the CPS gene is, therefore, dependent on the combined action of a distal and a promoter-proximal response unit.

The kappa promoter penta-decamer binding protein CBF-A interacts specifically with nucleophosmin in the nucleus only

CArG box-binding factor-A (CBF-A) interacts with the penta-decamer (pd) element that is a conserved sequence element within mouse Vkappa promoters. The pd element acts in synergy with the octamer element to stimulate kappa transcription, especially in later stages of B cell development. To get further insight in the mechanism for CBF-A action we have characterised its protein-protein interactions. We show here that CBF-A interacts specifically with nucleophosmin (NPM). This interaction occurs via the homo-oligomerisation domain of NPM and the N-terminus of CBF-A and was exclusive for the nuclear compartment while the two proteins failed to interact in the cytosol. In contrast, CBF-A formed homocomplexes in this compartment. CBF-A was also shown to localise to the nucleoli, most likely dependent on a functional interaction with NPM. Lastly, the sequence fine specificity of CBF-A complexes in the nucleus and cytoplasm were found to differ and nuclear protein-DNA complexes were shown to contain NPM. Thus, CBF-A participates in several protein-protein interactions that may modulate its subcellular localisation and target gene specificity.

Identification of two novel shear stress responsive elements in rat angiotensin I converting enzyme promoter

Mechanical forces contribute to maintenance of cardiovascular homeostasis via the control of release and production of vasoactive substances. We demonstrated previously that shear stress decreases rat ACE activity and expression. Using a reporter gene approach and mutagenesis, we show now that the classic shear stress responsive element or SSRE (GAGACC) contained within 1,274 bp of this promoter is not functional in response to shear stress (15 dyn/cm2, 18 h) [for the wild-type ACE promoter (WLuc), static control (C) = 107 ± 6.5%, shear stress (SS) = 65.9 ± 9.4%, n = 8; for the promoter with the classic SSRE mutated (WSS-mut), C = 100 ± 8.2%, SS = 60.2 ± 5.2%, n = 10, respectively]. Analysis of progressive deletion mutants unraveled a 57-bp fragment, position −251 to −195, from the transcription start site, containing functional SSRE (for WLuc, C = 107 ± 6.5%, SS = 65.9 ± 9.4%, n = 8; for 378, C = 100 ± 6.4%, SS = 60.4 ± 4.3%, n = 11; for 251, C = 99.7 ± 2.6%, SS = 63.2 ± 5.5%, n = 7; for 194, C = 104.6 ± 8.1%, SS = 92.4 ± 6.9%, n = 9). This fragment responded to shear stress even in the context of a heterologous promoter. Finally, functional analysis of mutated candidate regulatory elements identified by gel shift, DNase I footprint, and conservation of aligned sequences revealed that only the double mutant (Barbie/GAGA-mut) but not isolated disruption of the Barbie (WBarbie-mut) or the GAGA (WGAGA-mut) prevented the shear-stress-induced response (for Barbie/GAGA-mut, C = 97.9 ± 5%, SS = 99.4 ± 7.2%, n = 6; for WBarbie-mut, C = 106.1 ± 8.6%, SS = 65.9 ± 9.4%, n = 6; for WGAGA-mut, C = 100.1 ± 2.9%, SS = 66.7 ± 1.6, n = 6;). Taken together, these data provide direct evidence for the new role of Barbie and GAGA boxes in mediating the shear-stress-induced downregulation of rat ACE expression and demonstrate that the classic SSRE (GAGACC) is not functional under the experimental conditions tested.

Multiple type A/B heterogeneous nuclear ribonucleoproteins (hnRNPs) can replace hnRNP A1 in mouse hepatitis virus RNA synthesis

Heterogeneous nuclear ribonucleoprotein (hnRNP) A1 has previously been shown to bind mouse hepatitis virus (MHV) RNA at the 3' end of both plus and minus strands and modulate MHV RNA synthesis. However, a mouse erythroleukemia cell line, CB3, does not express hnRNP A1 but still supports MHV replication, suggesting that alternative proteins can replace hnRNP A1 in cellular functions and viral infection. In this study, we set out to identify these proteins. UV cross-linking experiments revealed that several CB3 cellular proteins similar in size to hnRNP A1 interacted with the MHV RNA. These proteins were purified by RNA affinity column with biotinylated negative-strand MHV leader RNA and identified by mass spectrometry to be hnRNP A2/B1, hnRNP A/B, and hnRNP A3, all of which belong to the type A/B hnRNPs. All of these proteins contain amino acid sequences with strong similarity to the RNA-binding domains of hnRNP A1. Some of these hnRNPs have previously been shown to replace hnRNP A1 in regulating RNA splicing. These proteins displayed MHV RNA-binding affinity and specificity similar to those of hnRNP A1. hnRNP A2/B1, which is predominantly localized to the nucleus and shuttles between the nucleus and the cytoplasm, was shown to relocalize to the cytoplasm in MHV-infected CB3 cells. Furthermore, overexpression of hnRNP A/B in cells enhanced MHV RNA synthesis. Our findings demonstrate that the functions of hnRNP A1 in MHV RNA synthesis can be replaced by other closely related hnRNPs, further supporting the roles of cellular proteins in MHV RNA synthesis.

Functional domains involved in the interaction between Orc1 and transcriptional repressor AlF-C that bind to an origin/promoter of the rat aldolase B gene

The promoter of the rat aldolase B (AldB) gene functions in vivo as an origin of DNA replication in the cells in which transcription of the gene is repressed. Previously, we identified two closely related DNA-binding proteins, AlF-C1 and AlF-C2, which repressed the AldB gene promoter. We also reported that the binding site of these proteins, site C, is one of the required DNA elements of the AldB gene origin/promoter for autonomously replicating activity in transfected cells. In the present study, we show that AlF-C1 and AlF-C2 bind directly to Orc1, a subunit of the origin recognition complex (ORC). Deletion analyses revealed a functional domain in AlF-C2 for binding to Orc1, which is located separately from the DNA-binding domain. In addition, we found a novel protein-interacting domain in Orc1 required for the binding of AlF-C2, which was conserved in human, mouse and Chinese hamster, but not in Drosophila, frog and yeast. Thus, it is assumed that in mammalian cells, sequence- specific DNA-binding proteins are involved in recruiting ORC to regulate replication initiation and/or transcription repression.

Mast cells mediate substance P-induced bladder inflammation through an NK(1) receptor-independent mechanism

The role of neurokinin-1 receptors (NK1R) in the interaction between mast cells and substance P (SP) in bladder inflammation was determined. Mast cell-deficient Kit(W)/Kit(W-v), congenic normal (+/+), and Kit(W)/Kit(W-v) mice that were reconstituted with bone marrow cells isolated from NK1R(-/-) mice were challenged by instillation of SP, antigen, or saline into the urinary bladder. Twenty-four hours after challenge, the bladders were prepared for morphological assessment and gene expression. SP-induced bladder inflammation was mast cell dependent and did not require NK1R expression on the mast cell. Cluster analysis identified functionally significant genes that were dependent on the presence of mast cells for their upregulation regardless of stimulus. Those include serine protein inhibitor 2.2, maspin, mitogen- and stress-activated protein kinase 2, and macrophage colony-stimulating factor 1. Our findings demonstrate that while mast cells are essential for both antigen- and SP-induced bladder inflammation, there are common genes and unique genes expressed in each type of inflammatory reaction. When combined with unique animal models, gene array analysis provides a useful approach for identifying and characterizing pathways involved in bladder inflammation.

Identification of a novel AU-rich-element-binding protein which is related to AUF1

The AU-rich element (ARE) is an important instability determinant for a large number of early-response-gene mRNAs. AREs also mediate the stabilization of certain pro-inflammatory mRNAs, such as tumour necrosis factor (TNF)-alpha and cyclo-oxygenase-2 (COX-2), in response to inflammatory stimuli. To understand how AREs control mRNA stability, it is necessary to identify trans-acting factors. We have purified a new ARE-binding protein and identified it as CArG box-binding factor-A (CBF-A). The amino acid sequence of CBF-A is highly similar to that of the ARE-binding protein AUF1. Recombinant CBF-A bound the COX-2 and TNF-alpha AREs, but not a non-specific control RNA. In contrast, in an electrophoretic-mobility-shift assay (EMSA) of crude RAW 264.7 macrophage-like cell extracts, an antiserum that recognizes both AUF1 and CBF-A failed to supershift complexes formed on the TNF-alpha ARE, but did supershift a complex specific for the COX-2 ARE. CBF-A exists as two isoforms, p37 and p42, that differ by a 47-amino-acid insertion close to the C-terminus. By expressing epitope-tagged isoforms of CBF-A it was shown that the p42 isoform binds the COX-2 ARE in EMSA of crude cell extracts. In a HeLa-cell tetracycline-regulated reporter system, overexpression of the p42 CBF-A isoform resulted in stabilization of a COX-2 ARE reporter mRNA. Epitope-tagged p42 CBF-A expressed in HeLa cells co-immunoprecipitated with endogenous COX-2 mRNA, but not glyceraldehyde-3-phosphate dehydrogenase mRNA, as shown by reverse-transcription PCR. The similarity between CBF-A and AUF1 suggests that CBF-A could be re-named AUF2.