cDNA sequence of a Drosophila melanogaster gene, Dfur1, encoding a protein structurally related to the subtilisin-like proprotein processing enzyme furin

Screening a genomic library of Drosophila melanogaster DNA with a human fur cDNA probe resulted in the isolation of DNA clones that apparently belonged to two different DNA regions of the Drosophila genome. Subsequently, corresponding Drosophila cDNA clones were isolated. Nucleotide sequence analysis indicated that these cDNA clones originated from two different genes, which were called Dfur1 and Dfur2. From overlapping Dfur1 cDNA clones, a composite cDNA could be constructed and analysis of its nucleotide sequence revealed the coding sequence for a protein of 899 amino acid residues. This protein, designated Dfurin1, exhibited striking sequence homology to human furin and contained the same protein domains except for the cysteine-rich region. Furthermore, unlike human furin, Dfurin1 possessed an extended amino-terminal region in which a potential transmembrane anchor was present.     

Chicken egg white cystatin. Molecular cloning, nucleotide sequence, and tissue distribution

A lambda gt11 chicken oviduct cDNA library was screened with a mixed synthetic oligonucleotide corresponding to amino acid residues 81-90 of chicken egg white cystatin, a cysteine proteinase inhibitor. Two initial cDNA clones of 367 and 431 bases were isolated. Both clones contained coding sequences for cystatin from amino acid residue 82 to the carboxyl end plus 3'-untranslated region and a poly(A)+ tail. The two clones utilized different polyadenylation signals located 55 nucleotides apart. Further screening of the library yielded a full-length cystatin cDNA. Sequence analysis indicated that cystatin contains an NH2-terminal extension of 23 amino acids which is probably a signal sequence. The cystatin cDNA hybridized to an mRNA of approximately 0.95 kilobase and was present in varying amounts in all chicken tissues examined. The highest concentration was found in the lung. Gizzard, brain, and heart contained lesser amounts of cystatin mRNA but considerably higher than oviduct. Among a limited number of embryonic tissues examined, significantly higher levels of the mRNA were found in liver and heart tissues when compared with the corresponding adult tissues. These results suggested that the expression of the chicken cystatin gene is tissue-dependent and under developmental control.     

The human cystatin C gene (CST3) is a member of the cystatin gene family which is localized on chromosome 20

The fourth gene from the human cystatin gene family of salivary-type cysteine-proteinase inhibitors has been isolated and partially characterized by DNA analysis. The gene, which we name CST3, codes for human cystatin C, and has the same organization as the CST1 gene for cystatin SN and the CST2 gene for cystatin SA. Southern analysis of EcoR I digested DNAs from 32 independent somatic cell hybrid clones hybridized to a probe from CST1 demonstrated that all members of the cystatin gene family segregate with human chromosome 20. These results indicate that the genes for salivary-type cystatins and cystatin C are members of a multigene family--the cystatin gene family.     

rDLG6: a novel homolog of Drosophila DLG expressed in rat brain

Drosophila DLG (Discs Large Tumor Suppresser Protein) is a component of septate junctions, and disruption of its gene leads to over growth of imaginal discs. Homologs of Drosophila DLG recently isolated from mammalian tissue have been classified as members of the MAGUK (Membrane Associated GUanylate Kinase) superfamily of proteins. Using a modified RT-PCR method applied to rat tissues, we have isolated cDNA clones encoding a novel MAGUK family member that we have named rDLG6. Immunoblot and immunohistochemical analyses revealed that rDLG6 protein is predominantly expressed in brain. GST pull-down assays showed that the PDZ domain of rDLG6 protein binds to the C-terminus of the AMPA (alpha-Amino-3-hydroxy-5-Methyl-isoxazole-4-Propionic Acid) receptor GluR2 subunit.     

Isolation and characterization of a sea urchin hsp 70 gene segment

Three clones containing Paracentrotus lividus sea urchin DNA sequences which cross-hybridize to Drosophila heat shock protein (hsp) 70 gene were isolated. The sequence arrangements in the three cloned DNA inserts were compared by restriction and cross-hybridization analysis. The results showed that they contain four different genes related to one Drosophila hsp 70 gene. One of these genes was subcloned, and two of the isolated fragments were shown to hybridize to genomic DNA and to RNA from heat-treated sea urchin embryo.     

Cloning and sequencing of cDNA encoding a rat salivary cysteine proteinase inhibitor inducible by beta-adrenergic agonists

The beta-adrenergic agonist isoproterenol induces a unique secretory protein (LM) in the salivary glands of developing and adult rats. In order to study the regulation of growth and gene expression by catecholamines, we have isolated and sequenced several cDNA clones encoding the LM protein. Each of the LM cDNA clones described identifies, by Northern blot analyses, a single mRNA species of approximately 900 bases in size. The mRNA encoding this secreted protein was not detected in submandibular glands or brains of untreated adult rats. Sequence analyses of the LM cDNA clones revealed a striking similarity to the family 2 of cysteine proteinase inhibitors. Furthermore, when purified LM protein was used to assay for inhibition of cysteine proteinases, the data demonstrated that it is indeed a type of cysteine proteinase inhibitor. This inhibitor, termed rat cystatin S, provides the first example of cysteine proteinase inhibitors that can be induced by beta-adrenergic agonists.     

Human cystatin, a new protein inhibitor of cysteine proteinases

A new low-molecular weight protein inhibitor of cysteine proteinases, human cystatin, was isolated from sera of patients with autoimmune diseases. It inhibits papain, human cathepsin H and cathepsin B. According to its partially determined amino-acid sequence, human cystatin is highly homologous to egg white cystatin, but only distantly related to stefin, the cytosolic protein inhibitor of cysteine proteinases isolated from human polymorphonuclear granulocytes. Very probably human cystatin is identical with human gamma-trace, a microprotein of known sequence but hitherto unknown function.     

Cloning of a cDNA encoding an Artemia franciscana Na/K ATPase alpha-subunit.

Clones of cDNA that code for an isoform of the Artemia franciscana Na/K ATPase alpha subunit (NaKA alpha) have been isolated. The sequence of the longest of these clones (pArATNa136) is 3595 nucleotides; it codes for a 1004-amino acid protein whose sequence is identical to that of two previously sequenced Artemia NaKA alpha peptides. The encoded protein is over 73% identical to Drosophila melanogaster and vertebrate NaKA alpha s, and 73.8% identical to another Artemia NaKA alpha isoform previously described (named alpha 2850 in this article). The two Artemia cDNA clones code for mRNAs of different size; the clone pArATNa136 codes for a 4.5-kb mRNA while the alpha 2850 clone codes for a 3.6-kb mRNA. The degree of homology and the different size of the mRNAs encoded by both cDNAs suggest that they code for two different isoforms of the protein.     

Molecular cloning and characterization of the genes encoding the two subunits of Drosophila melanogaster calcineurin.

Genomic clones containing the full coding sequences of the two subunits of the Ca2+/calmodulin-stimulated protein phosphatase, calcineurin, were isolated from a Drosophila melanogaster genomic library using highly conserved human cDNA probes. Three clones encoded a 19.3-kDa protein whose sequence is 88% identical to that of human calcineurin B, the Ca(2+)-binding regulatory subunit of calcineurin. The coding sequences of the Drosophila and human calcineurin B genes are 69% identical. Drosophila calcineurin B is the product of a single intron-less gene located at position 4F on the X chromosome. Drosophila genomic clones encoding a highly conserved region of calcineurin A, the catalytic subunit of calcineurin, were used to locate the calcineurin A gene at position 21 EF on the second chromosome of Drosophila and to isolate calcineurin A cDNA clones from a Drosophila embryonic cDNA library. The structure of the calcineurin A gene was determined by comparison of the genomic and cDNA sequences. Twelve exons, spread over a total of 6.6 kilobases, were found to encode a 64.6-kDa protein 73% identical to either human calcineurin A alpha or beta. At the nucleotide level Drosophila calcineurin A cDNA is 67 and 65% identical to human calcineurin A alpha and beta cDNAs, respectively. Major differences between human and Drosophila calcineurins A are restricted to the amino and carboxyl termini, including two stretches of repetitive sequences in the carboxyl-terminal third of the Drosophila molecule. Motifs characteristic of the putative catalytic centers of protein phosphatase-1 and -2A and calcineurin are almost perfectly conserved. The calmodulin-binding and auto-inhibitory domains, characteristic of all mammalian calcineurins A, are also conserved. A remarkable feature of the calcineurin A gene is the location of the intron/exon junctions at the boundaries of the functional domains and the apparent conservation of the intron/exon junctions from Drosophila to man.     

The engrailed locus of Drosophila: structural analysis of an embryonic transcript

cDNA clones originating from the engrailed gene of Drosophila have been isolated from recombinant phage libraries that were made using poly(A)+ RNA extracted from early embryos. The DNA sequence of one of these clones includes a homeo box, a 180 bp sequence present in several other Drosophila genes important in formation of body pattern during development. The homeo boxes found in the other Drosophila genes, as well as in cognate sequences from a wide range of segmented animals, including higher vertebrates, are highly conserved. By contrast, the homeo box within the engrailed gene diverges substantially and, unlike the other homeo boxes, is interrupted by an intervening sequence. The engrailed homeo box is located near the 3' end of a 1700 bp open reading frame. If translated, this sequence would produce a protein of unusual composition. We also show that a neighboring gene has a large region with strong homology to engrailed, and that it also contains a homeo box.     

Drosophila spectrin. II. Conserved features of the alpha-subunit are revealed by analysis of cDNA clones and fusion proteins

Drosophila alpha-spectrin cDNA sequences were isolated from a lambda gt11 expression library. These cDNA clones encode fusion proteins that include portions of the Drosophila alpha-spectrin polypeptide as shown by a number of structural and functional criteria. The fusion proteins elicited antibodies that reacted strongly with Drosophila and vertebrate alpha-spectrins and a comparison of cyanogen bromide peptide maps demonstrated a clear structural correspondence between one fusion protein and purified Drosophila alpha-spectrin. Alpha-spectrin fusion protein also displayed calcium-dependent calmodulin-binding activity in blot overlay experiments and one fusion protein bound specifically to both Drosophila and bovine brain beta-spectrin subunits on protein blots. A region of the Drosophila cDNA cross-hybridized at lowered stringency with an avian alpha-spectrin cDNA. Together these data show that the composition, structure, and binding properties of the spectrin family of proteins have been remarkably well conserved between arthropods and vertebrates. Drosophila cDNA hybridized to an mRNA of greater than or equal to 9 kb on blots of total Drosophila poly A+ RNA; and hybridized in situ to a single site in polytene region 62B, 1-7. This result and Southern blot analysis of genomic DNA indicate that the sequences are likely to be single copy in the Drosophila genome.     

A new multi-domain member of the cystatin superfamily expressed by Fasciola hepatica

Cystatins are cysteine protease inhibitors that are widespread in the plant and animal kingdoms. Cystatins are expressed by helminth parasites that may employ these proteins to regulate parasite cysteine protease activity and to modulate host immune responses. Here, we describe the cloning of a cDNA encoding a high molecular weight protein of Fasciola hepatica that contains two domains with significant identity to the cardinal cystatin signatures and four domains with degenerated cystatin signatures. This is the first report of a multi-domain cystatin in an invertebrate species. While cystatins are divided into three evolutionary related families, our phylogenetic analysis shows that all cystatin domains within this protein, like several other helminth cystatins, belong to the cystatin family 2. The DNA region encoding the domain 4 that is the best conserved at the level of its cystatin signatures was expressed in Drosophila cells and a recombinant protein was produced and purified. This protein was a potent inhibitor of the papain and of the major cysteine protease of F. hepatica, the cathepsin L1.     

Isolation and characterization of a gene encoding DNA topoisomerase I in Drosophila melanogaster.

We synthesized a DNA probe specific for the gene encoding eucaryotic DNA topoisomerase I by the polymerase chain reaction. The sequences of the primers for this reaction were deduced from the regions with extensive homology among the enzymes from the fission and budding yeasts, and the human. From the clones isolated by screening a Drosophila cDNA library with this DNA probe, two cDNA clones of 3.8 and 5.2 kb were characterized and completely sequenced. Both cDNA sequences contain an identical open reading frame for 972 amino acid residues. The 3.8 kb messenger RNA is likely generated by using a polyadenylation site 5' upstream to that used in generating the 5.2 kb mRNA. The predicted amino acid sequence shows that a segment of 420 amino acid residues at the amino terminus is hydrophilic, similar to the amino terminal 200 residues in the yeast and human enzymes. Furthermore, the Drosophila enzyme is unique in that the amino terminal 200 residues are enriched in serine and histidine residues; most of them are present in clusters. The rest of the Drosophila sequence is highly homologous to those from yeast and human enzymes. The evolutionarily conserved residues are identified and are likely the critical elements for the structure and function of this enzyme. A plasmid vector containing the cloned cDNA was constructed for the expression of Drosophila protein in Escherichia coli. The enzymatic and immunochemical analysis of the polypeptide produced in this heterologous expression system demonstrated that the expressed protein shares similar enzymatic properties and antigenic epitopes with DNA topoisomerase I purified from Drosophila embryos or tissue culture cells, thus establishing the bacterial expression system being useful for the future structure/function analysis of the Drosophila enzyme.