Despite WT1 binding sites in the promoter region of human and mouse nucleoporin glycoprotein 210, WT1 does not influence expression of GP210

BACKGROUND: Glycoprotein 210 (GP210) is a transmembrane component of the nuclear pore complex of metazoans, with a short carboxyterminus protruding towards the cytoplasm. Its function is unknown, but it is considered to be a major structural component of metazoan nuclear pores. Yet, our previous findings showed pronounced differences in expression levels in embryonic mouse tissues and cell lines. In order to identify factors regulating GP210, the genomic organization of human GP210 was analyzed in silico. RESULTS: The human gene was mapped to chromosome 3 and consists of 40 exons spread over 102 kb. The deduced 1887 amino acid showed a high degree of alignment homology to previously reported orthologues. Experimentally we defined two transcription initiation sites, 18 and 29 bp upstream of the ATG start codon. The promoter region is characterized by a CpG island and several consensus binding motifs for gene regulatory transcription factors, including clustered sites associated with Sp1 and the Wilms' tumor suppressor gene zinc finger protein (WT1). In addition, distal to the translation start we found a (GT)n repetitive sequence, an element known for its ability to bind WT1. Homologies for these motifs could be identified in the corresponding mouse genomic region. However, experimental tetracycline dependent induction of WT1 in SAOS osteosarcoma cells did not influence GP210 transcription. CONCLUSION: Although mouse GP210 was identified as an early response gene during induced metanephric kidney development, and WT1 binding sites were identified in the promoter region of the human GP210 gene, experimental modulation of WT1 expression did not influence expression of GP210. Therefore, WT1 is probably not regulating GP210 expression. Instead, we suggest that the identified Sp binding sites are involved

Ets-1 Confers Cranial Features on Neural Crest Delamination

Neural crest cells (NCC) have the particularity to invade the environment where they differentiate after separation from the neuroepithelium. This process, called delamination, is strikingly different between cranial and trunk NCCs. If signalings controlling slow trunk delamination start being deciphered, mechanisms leading to massive and rapid cranial outflow are poorly documented. Here, we show that the chick cranial NCCs delamination is the result of two events: a substantial cell mobilization and an epithelium to mesenchyme transition (EMT). We demonstrate that ets-1, a transcription factor specifically expressed in cranial NCCs, is responsible for the former event by recruiting massively cranial premigratory NCCs independently of the S-phase of the cell cycle and by leading the gathered cells to straddle the basal lamina. However, it does not promote the EMT process alone but can cooperate with snail-2 (previously called slug) to this event. Altogether, these data lead us to propose that ets-1 plays a pivotal role in conferring specific cephalic characteristics on NCC delamination

Conditional up-regulation of IL-2 production by p38 MAPK inactivation is mediated by increased Erk1/2 activity

The p38 mitogen-activated protein kinase regulates many cellular processes in almost all eukaryotic cell types. In T cells, p38 was shown to regulate thymic development and cytokine production. Here, the role of p38 on interleukin-2 (IL-2) production by human peripheral blood CD4+ T cells was examined. When T cells were stimulated under weak stimulation conditions, pharmaceutical and molecular p38 inhibitors induced a dramatic increase of IL-2 production. In contrast, IL-2 levels were not affected significantly when strong stimulation was provided to T cells. The increase in IL-2 production, following p38 inhibition, was associated with a strong up-regulation of extracellular signal-regulated kinase (Erk)1/2 activity. Furthermore the Erk inhibitor U0126 was able to counteract the effect of p38 inhibition on IL-2 production, supporting the conclusion that p38 mediates its effect through Erk. These results suggest that the p38 kinase, through its ability to control Erk activation levels, acts as a gatekeeper, which prevents inappropriate IL-2 production. Also, the finding that p38 acts in a strength-of-stimulation-dependent way provides an explanation for previously reported, contradictory results regarding the role of this kinase in IL-2 expression. © Society for Leukocyte Biology

Conditional up-regulation of IL-2 production by p38 MAPK inactivation is mediated by increased Erk1/2 activity

The p38 mitogen-activated protein kinase regulates many cellular processes in almost all eukaryotic cell types. In T cells, p38 was shown to regulate thymic development and cytokine production. Here, the role of p38 on interleukin-2 (IL-2) production by human peripheral blood CD4+ T cells was examined. When T cells were stimulated under weak stimulation conditions, pharmaceutical and molecular p38 inhibitors induced a dramatic increase of IL-2 production. In contrast, IL-2 levels were not affected significantly when strong stimulation was provided to T cells. The increase in IL-2 production, following p38 inhibition, was associated with a strong up-regulation of extracellular signal-regulated kinase (Erk)1/2 activity. Furthermore the Erk inhibitor U0126 was able to counteract the effect of p38 inhibition on IL-2 production, supporting the conclusion that p38 mediates its effect through Erk. These results suggest that the p38 kinase, through its ability to control Erk activation levels, acts as a gatekeeper, which prevents inappropriate IL-2 production. Also, the finding that p38 acts in a strength-of-stimulation-dependent way provides an explanation for previously reported, contradictory results regarding the role of this kinase in IL-2 expression