We report that the tumor neurosis factor homolog APRIL (a proliferation-inducing ligand) stimulates in vitro proliferation of primary B and T cells and increases spleen weight due to accumulation of B cells in vivo. APRIL functions via binding to BCMA (B cell maturation antigen) and TACI (transmembrane activator and CAML-interactor) and competes with TALL-I (also called BLyS or BAFF) for receptor binding. Soluble BCMA and TACI specifically prevent binding of APRIL and block APRIL-stimulated proliferation of primary B cells. BCMA-Fc also inhibits production of antibodies against keyhole limpet hemocyanin and Pneumovax in mice, indicating that APRIL and/or TALL-I signaling via BCMA and/or TACI are required for generation of humoral immunity. Thus, APRIL-TALL-I and BCMA-TACI form a two ligands-two receptors pathway involved in stimulation of B and T cell function.

Long-term plasticity of the central nervous system (CNS) involves induction of a set of genes whose identity is incompletely characterized. To identify candidate plasticity-related genes (CPGs), we conducted an exhaustive screen for genes that undergo induction or downregulation in the hippocampus dentate gyrus (DG) following animal treatment with the potent glutamate analog, kainate. The screen yielded 362 upregulated CPGs and 41 downregulated transcripts (dCPGs). Of these, 66 CPGs and 5 dCPGs are known genes that encode for a variety of signal transduction proteins, transcription factors, and structural proteins. Seven novel CPGs predict the following putative functions: cpg2--a dystrophin-like cytoskeletal protein; cpg4--a heat-shock protein: cpg16--a protein kinase; cpg20--a transcription factor; cpg21--a dual-specificity MAP-kinase phosphatase; and cpg30 and cpg38--two new seven-transmembrane domain receptors. Experiments performed in vitro and with cultured hippocampal cells confirmed the ability of the cpg-21 product to inactivate the MAP-kinase. To test relevance to neural plasticity, 66 CPGs were tested for induction by stimuli producing long-term potentiation (LTP). Approximately one-fourth of the genes examined were upregulated by LTP. These results indicate that an extensive genetic response is induced in mammalian brain after glutamate receptor activation, and imply that a significant proportion of this activity is coinduced by LTP. Based on the identified CPGs, it is conceivable that multiple cellular mechanisms underlie long-term plasticity of the nervous system.

To isolate transcription factors important in the regulation of the human interleukin-3 (IL-3) gene, we screened a gt11 cDNA library, constructed from phytohemagglutinin-stimulated human T-cell RNA, with a probe containing regulatory sequences in the upstream region of the IL-3 gene (located from bp ؊165 to ؊128 and referred to as the DNase I footprint A region). We isolated a 0.96-kb cDNA that encoded a basic amino acid domain and a leucine zipper domain and used the ''rapid amplification and cloning of 3 ends'' technique to isolate the 3 half of the cDNA clone, generating a 1.9-kb full-length cDNA clone. Using in vitro-translated protein, which we call NF-IL3A, we defined the IL-3 promoter sequences bound by NF-IL3A in DNase I footprinting assays as TAATTACGTCTG and, using gel shift assays, defined ATTACG as the minimal sequence Interleukin-3 (IL-3) is a multilineage hematopoietic growth factor which stimulates the proliferation of hematopoietic progenitor cells and enhances the functional activity of mature effector cells (27,36). The expression of IL-3 is restricted to activated, but not resting, T cells, natural killer (NK) cells, and mast cell lines (9,27,29). In order to examine the regulatory mechanisms controlling the expression of IL-3, several investigators, including ourselves, have identified regulatory elements in the 5Ј-flanking region of the IL-3 promoter (3,10,13,19,21,22,33,35). These regulatory elements include a consensus AP-1 binding site, which can bind c-Fos/c-Jun heterodimers (13), several consensus binding sites for ets proteins (13), a CD28 response element (12, 35), and two regions identified by DNase I footprinting experiments as the A region and the B region (35). The A region contains regulatory sequences important in the inducible expression of 33,35), and methylation interference experiments have identified several distinct regions within this A region that are involved in DNAprotein interactions (10, 37). Electrophoretic mobility shift assays (EMSAs) combined with UV cross-linking have identified several proteins of 56 to 65 kDa that are capable of binding to the IL-3 A region (37).To identify and characterize IL-3 A region-binding proteins, we screened a phytohemagglutinin (PHA)-stimulated human T-cell cDNA gt11 expression library with a 32 P-labeled, multimerized, double-stranded IL-3 A region synthetic oligonucleotide probe. Approximately one million recombinant clones were screened, and one clone that generated a ␤-galactosidase fusion product that bound to the IL-3 A region but not to unrelated control DNA was identified. DNA sequence analysis of this clone demonstrated the presence of a potential DNAbinding basic-amino-acid region and a leucine zipper repeat. The 3Ј portion of the cDNA clone was not present, so rapid amplification and cloning of 3Ј ends (3Ј RACE) was performed to generate a full-length cDNA clone.A 1.9-kb full-length cDNA that contains the entire coding region for a 58-kDa protein that we call NF-IL3A was generated. In vitro-translated NF-IL3A binds specifi...

The cyclic AMP (cAMP) response element-binding protein (CREB) has been demonstrated to be a key mediator of cellular promoter response to cAMP. The binding site for this protein in many cellular cAMP inducible promoters (CRE) contains the palindrome sequence TGACGTCA, which contains two half-sites for CREB binding. A related promoter element, with the core sequence TGACG, has significant homology to an APl-binding site and contains only one half-site for CREB binding. A group of factors known as activating transcription factors (ATF) have been found to bind to the latter and related sequences found upstream of early adenovirus promoters induced by ElA, and these factors are highly homologous to the CREB protein. We wished to characterize CREB, c-jun, and c-fos binding to these sites in the somatostatin gene (CRE) and in the adenovirus early region 3 promoter (E3IATF). Oligonucleotides complementary to each of these sites were usedin gel retardation assays with in vitro-translated CREB protein. These studies indicated that CREB bound

Transcription of the adenovirus early region 3 promoter is strongly induced by the adenovirus ElA protein. Previous DNase I footprinting has indicated that four regions in this promoter serve as binding sites for HeLa nuclear proteins. These include binding sites for NF-1 (site IV), AP1 (site III), CREB/activating transcription factor (ATF) (site II), and TATA (site I). To determine the relative importance of these sites in both the in vivo and in vitro transcriptional regulation of the E3 promoter, oligonucleotide-directed mutagenesis of these sites was performed. Each of these constructs was assayed by transfection onto HeLa cells in the presence of either d1434, an ElA/ElB deletion mutant, or wild-type adenovirus. Mutations of either the ATFor APl-binding sites but not the TATAand NFl-binding sites resulted in severe decreases in both basal and ElA/ElB-induced transcriptional levels. These constructs were also assayed in in vitro transcription assays with cellular extracts prepared from d1434-infected or wild-type-adenovirus-infected HeLa cells. The wild-type E3 promoter was transcribed approximately 30 times more efficiently in extracts containing the E1A/E1B proteins compared with extracts lacking these proteins. Mutations of either the TATA element, the ATF site, or the APl-binding site decreased both basal and ElA/ElB-induced transcriptional levels. Gel retardation analysis using these extracts indicated that the binding to ATF, AP1, or NF1 oligonucleotides was not altered in the presence of the E1A/E1B proteins compared with extracts lacking these proteins. Northern (RNA) blot analysis of c-jun and CREB RNA prepared from wild-type adenovirus and d1434-infected cells indicated that the levels of these RNAs were not altered by the ElA/E1B proteins. Immunoprecipitation of AP1 and CREB from both d1434-and wild-type-adenovirus-infected cells indicated that the amounts of these proteins were not significantly altered. These results suggest that ElA/ElB-induced activation of the E3 promoter does not involve activation of transcription factor genes nor a change in the DNA binding activity of important promoter-binding components. Our results are consistent with a model in which the EIA/ElB proteins either directly or indirectly alter the interactions of factors that bind to the basal E3 promoter transcription complex, thereby inducing transcription.