We have previously shown that the cell line 6D5(451) chronically infected with the HIV-1 isolate HTLV-III(451), secretes the HIV-1 envelope glycoproteins gp120 and gp160 in the extracellular medium. The HTLV-III(451) gp120 and gp160 were purified by sequential affinity chromatographic steps using a monoclonal antibody to HIV-1 gp41 and an anti-HIV-1-positive human serum. Amino acid sequence analysis of gp120 and gp160 showed the loss of the signal peptide. Digestion of the purified gp120 and gp160 with endoglycosidases revealed that both proteins are heavily glycosylated and contain complex carbohydrates, in contrast to the intracellular form of gp160 which has been shown to contain mannose-rich immature sugars. Competitive binding analysis showed that while both gp120 and gp160 bind CD4, the affinity of gp160 was five times lower than that of gp120. Both gp120 and gp160 inhibited syncytia formation by HIV-1-infected cells when mixed with CD4+ cells. Furthermore, both gp120 and gp160 had strong mitogenic effects on the T cells from HIV-1-infected gibbons but not on cells from uninfected gibbons.

Summary In the absence of EBF1, B cell development is arrested at an uncommitted progenitor stage that exhibits increased lineage potentials. Previously, we investigated the roles of EBF1 (E) and its DNA binding partner Runx1 (R) by evaluating B lymphopoiesis in single (Ehet and Rhet) and compound haploinsufficent (ERhet) mice. Here, we demonstrate that reduced Ebf1 gene dosage results in the inappropriate expression of NK cell lineage-specific genes in B cell progenitors. Moreover, prolonged expression of Ly6a/Sca-1 suggested the maintenance of a relatively undifferentiated phenotype. These effects were exacerbated by reduced expression of Runx1 and occurred despite expression of Pax5. Repression of inappropriately expressed genes was restored in most pre-B and all immature B cells of ERhet mice. Enforced EBF1 expression repressed promiscuous transcription in pro-B cells of ERhet mice and in Ebf1−/−Pax5−/− fetal liver cells. Together, our studies suggest that normal levels of EBF1 are critical for maintaining B cell identity by directing repression of non-B cell-specific genes.

Three distinctly different alleles of the metallothionein gene Mtn have been identified in natural Drosophila melanogaster populations: Mtn.3, Mtn1, and Dp(Mtn1), where the latter designates a tandem duplication of Mtn1. In Drosophila simulans, only Mtn.3-type alleles have been found. It has been suggested that Mtn.3 is the ancestral allele and demonstrated that a presumed two-step transition from Mtn.3 to Mtn1 to Dp(Mtn1) is accompanied by an approximate 5-fold increase in RNA levels. We analyzed the evolutionary genetics of the Mtn locus of Drosophila ananassae, a distant relative of D. melanogaster and D. simulans within the melanogaster species group. The Mtn gene of D. ananassae is most similar to Mtn.3: (i) it is identical with Mtn.3 at the amino acid level, but differs from Mtn1 in its terminal codon; (ii) its 3' UTR contains a characteristic extra DNA segment of about 50 bp which is present in Mtn.3, but lacking in Mtn1; (iii) duplications of Mtn were not found in a worldwide sample of 110 wild D. ananassae chromosomes. However, the intron of the Mtn gene in D. ananassae is only 69 bp long, whereas the length of the Mtn.3 and Mtn1 introns is 265 bp; and it lacks a polypyrimidine stretch upstream of the 3' splice site in contrast to the much greater pyrimidine-richness found in the Mtn.3 and Mtn1 introns. A short intron (67 bp) was also identified in a D. pseudoobscura Mtn allele, suggesting that the short intron is the ancestral form and that the transition from the short to the long intron occurred within the melanogaster species group.(ABSTRACT TRUNCATED AT 250 WORDS)

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Mast cells play crucial roles in both innate and adaptive immune responses. Evidence in our laboratory suggests that the ZFP521 (Evi3/ZNF521/EHZF) transcription factor orchestrates key pathways required for proper development and function of mast cells. ZFP521 is a nuclear protein that contains 30 zinc fingers. ZFP521 is important for the renewal and development of hematopoietic cells. Here, we demonstrate that ZFP521 is expressed highly in murine mast cells. To address the intrinsic roles of ZFP521 in mast cells, we developed a model system in which Zfp521 gene expression is ablated conditionally in mast cells of mice with floxed alleles (Zfp521 cKO mice) by mast cell-specific Cre (Mcpt5-Cre transgene). Zfp521 is required for normal numbers of mast cells in the peritoneal cavity (PMC). In part, the reduction of PMC may be due to the reduced expression of CD117 (c-Kit) on Zfp521 cKO-derived mast cells. Both CD117 and its ligand, Stem Cell Factor (SCF), are essential for mast cell development in the bone marrow. Additionally, the expression of several transcription factors, including GATA-1, GATA-2 and GATA-3, which regulate mast cell development and function is reduced in bone marrow-derived Zfp521 cKO mast cells. Together, our data provide insights into 1) a novel role for ZFP521 in hematopoiesis, and 2) the transcriptional regulatory network that governs the development and function of mast cells.