Molecular cloning of chitinase cDNAs from the silkworm, Bombyx mori and the fall webworm, Hyphantria cunea

cDNAs encoding chitinases were cloned and characterized from Bombyx mori and Hyphantria cunea, and their gene expression during the metamorphosis was also studied. The chitinase cDNA from B. mori encodes a protein of 565 amino acids with a calculated molecular mass of 63.4 kDa and the H. cunea chitinase cDNA encodes a protein of 553 amino acids with a calculated molecular mass of 62.0 kDa. Amino acid alignment of the two chitinases revealed 75% homology and 77-80% with M. sexta chitinase. The putative cleavage site of the signal peptide was between amino acid residues 20 and 21 for both chitinases. There were three potential N-glycosylation sites in the chitinase of B. mori at the amino acid residues 86-89, NFTS 304-307, NATG, 398-401, NYTV, whereas two potential N-glycosylation sites were present at the amino acid residues 86-89, NFTA and 304-307, NATG, in that of H. cunea. Southern blot analysis of total genomic DNA suggested that the B. mori genome has only one chitinase gene detectable by the cDNA probe and the H. cunea genome has one or two chitinase gene copies. Northern analysis indicated that gene expression was up-regulated during the molting process, larval-pupal transformation and pupal-adult transformation, when enzymatic degradation of cuticle was occurring.

Cl- secretion induced by 5-hydroxytryptamine and calcitonin gene-related peptide in rat tracheal epithelia

The effects of 5-hydroxytryptamine (5-HT) and calcitonin gene-related peptide (CGRP), which are colocalized in nerve terminals in the airway, on Cl- secretion in rat tracheal epithelia were tested. Short-circuit current (Isc) was measured after rat tracheal epithelial monolayers were cultured on porous filters. In rat tracheal monolayers 5-HT and CGRP increased Isc upon addition to the serosal compartment, in a dose-dependent manner with EC50 values at 5 micromol/l and 5 nmol/l, respectively. The responses were dependent on the presence of Cl- in the bathing solution and were inhibited by 100 micromol/l bumetanide. When 5-HT or CGRP was added after the administration of forskolin, the responses were not observed. 5-HT and CGRP increased the intracellular cAMP concentration. Low-Ca2+ buffer (0.1 mmol/l) and pretreatment with BAPTA/AM (10 micromol/l), thapsigargin (1 micromol/l) or indomethacin (10 micromol/l) did not affect the responses to 5-HT and CGRP. The 5-HT-induced response was not inhibited by 5-HT2 and/or 5-HT4 antagonists. These results indicate that in the rat tracheal epithelia 5-HT and CGRP increase Cl- secretion by an increase in intracellular cAMP concentration via direct activation of basolateral receptors, and that the response to 5-HT is not mediated via 5-HT4 receptors.

Isolation and characterization of the cDNA encoding the prophenoloxidase of fall webworm, hyphantria cunea

Two kinds of cDNA clones encoding prophenoloxidases (ProPO; zymogen of phenoloxidase (monophenol, L-dopa: oxygen oxydoreductase, EC 1.14.18.1)) were isolated by polymerase chain reaction (PCR) followed by screening of cDNA library that was prepared from whole larvae of the fall webworm, Hyphantria cunea (Lepidoptera, Arctiidae). The cDNAs encode 681 and 697 amino acids with molecular masses of 78.2 and 80.2 kDa, respectively. Deduced amino acid sequence homology between the two H. cunea ProPOs are only 49% whereas the homology against other insect ProPOs ranged from about 40 to 72%. The phylogenic analysis showed that the insect ProPOs are grouped mainly into two families. A putative proteolytic cleavage site for enzyme activation was identical to other insect ProPOs. The conserved copper binding sites were 84-62% homologous to arthropod ProPOs. Two additional highly conserved regions were found in the carboxy terminal. Furthermore, like other insect prophenoloxidases, hydrophobic signal peptide sequences were absent in the deduced ProPOs from H. cunea. Southern blot analysis indicated that the H. cunea ProPO1 is present as a single copy in the genome. Northern blot analysis showed that the expression of the ProPO genes were concentrated in mid-instar larvae, but were much lower in other developmental stages.

An alteration in the structure of the minor groove of duplex DNA induced by the formation of an intermolecular d(GA)n:d(GA)n.d(TC)n triplex

A simple homopolymeric purine:purine.pyrimidine, d(GA)n:d(GA)n.d(TC)n, triplex DNA was generated in the presence of magnesium ion at neutral pH. Hydrogen bonding of the N7 positions of guanines and adenines was investigated by 7-deaza base substitutions and protection from chemical modification by dimethyl sulfate (DMS). Chemical modification of this triplex with DMS revealed an unexpected triplex specific hypermodification in the N3 positions of the adenines in addition to the protection in the N7 positions of the guanines. The significance of this increase in the chemical accessibility of the N3 positions of adenines in the minor groove and possible relevance of dehydration to the mechanism of triplex formation and stability is discussed.

Cloning of a SH3 domain-containing proline-rich protein, p85SPR, and its localization in focal adhesion

A mouse thymus cDNA expression library was screened with monoclonal antibody (mAb), B16-5 which binds to common epitope in SH3 domains of phospholipase C-gamma 1 (PLC-gamma 1) and Nck. We have determined the complete nucleotide sequence of one of several positive clones. The 4,172 bp cDNA clone (GenBank Accession No. U96634) encodes a SH3 domain-containing protein of 646 amino acids. Besides the SH3 domain, the predicted protein has a proline-rich region, nuclear localization signals, and leucine zipper motifs. The expressed protein in Sf9 insect cell exhibits a polypeptide of 85 kDa on SDS-PAGE. The protein is widely distributed in rat tissue with an especially high level of expression in brain and testis. Interestingly, the specific antibodies detected four related proteins of different size (75, 85, 90 and 105 kDa) in brain. In A431 cell, p85SPR is enriched at focal adhesion points indicating that the protein may interact with protein(s) in focal complexes.

The presence of a Sar1 gene family in Brassica campestris that suppresses a yeast vesicular transport mutation Sec12-1

Two new members (Bsar1a and Bsar1b) of the Sar1 gene family have been identified from a flower bud cDNA library of Brassica campestris and their functional characteristics were analyzed. The two clones differ from each other at 14 positions of the 193 amino acid residues deduced from their coding region. The amino acid sequences of Bsar1a and Bsar1b are most closely related to the Sar1 family, genes that function early in the process of vesicle budding from the endoplasmic reticulum (ER). The sequences contain all the conserved motifs of the Ras superfamily (G1-G4 motifs) as well as the distinctive structural feature near the C-terminus that is Sar1 specific. Our phylogenetic analysis confirmed that these two clones can indeed be considered members of the Sar1 family and that they have a close relationship to the ARF family. The Bsar1 proteins, expressed in Escherichia coli, cross-reacted with a polyclonal antibody prepared against Saccharomyces cerevisiae Sar1 protein. It also exhibited GTP-binding activity. Genomic Southern blot analysis, using the 3'-gene-specific regions of the Bsar1 cDNAs as probes, revealed that the two cDNA clones are members of a B. campestris Sar1 family that consists of 2 to 3 genes. RNA blot analysis, using the same gene-specific probes, showed that both genes are expressed with similar patterns in most tissues of the plant, including leaf, stem, root, and flower buds. Furthermore, when we placed the two Bsar1 genes under the control of the yeast pGK1 promoter into the temperature-sensitive mutant yeast strain S. cerevisiae Sec12-1, they suppressed the mutation which consists of a defect in vesicle transport. The amino acid sequence similarity, the GTP-binding activity, and the functional suppression of the yeast mutation suggest that the Bsar1 proteins are functional homologues of the Sar1 protein in S. cerevisiae and that they may perform similar biological functions.

Protein purification and nucleotide sequence of a lysozyme from the bacteria-induced larvae of the fall webworm, Hyphantria cunea

A protein with lytic activity against Micrococcus luteus was purified from the hemolymph of the fall webworm, Hyphantria cunea, larvae challenged with live E. coli. A bacteriolytic protein of about 14,000 daltons in mass was purified by cation exchange chromatography and reverse-phased HPLC. The optimum pH and optimum temperature range for activity were around pH 6.2 and 50 degrees C, respectively, in a 100 mM phosphate buffer. The amino-terminal amino acid sequence of this protein was determined and the corresponding cDNA was isolated and analyzed. The deduced protein of 142 amino acid residues was composed of a putative leader sequence of 20 residues and the mature enzyme of 122 residues. The cloned lysozyme gene was strongly induced in response to bacterial injection, implying that the enzyme is a part of the immune response of H. cunea. Comparison with other known lysozyme sequences shows that our lysozyme belongs to the chicken lysozyme.

Expressed sequence tags of Chinese cabbage flower bud cDNA

We randomly selected and partially sequenced cDNA clones from a library of Chinese cabbage (Brassica campestris L. ssp. pekinensis) flower bud cDNAs. Out of 1216 expressed sequence tags (ESTs), 904 cDNA clones were unique or nonredundant. Five hundred eighty-eight clones (48.4%) had sequence homology to functionally defined genes at the peptide level. Only 5 clones encoded known flower-specific proteins. Among the cDNAs with no similarity to known protein sequences (628), 184 clones had significant similarity to nucleotide sequences registered in the databases. Among these 184 clones, 142 exhibited similarities at the nucleotide level only with plant ESTs. Also, sequence similarities were evident between these 142 ESTs and their matching ESTs when compared using the deduced amino acid sequences. Therefore, it is possible that the anonymous ESTs encode plant-specific ubiquitous proteins. Our extensive EST analysis of genes expressed in floral organs not only contributes to the understanding of the dynamics of genome expression patterns in floral organs but also adds data to the repertoire of all genomic genes.

Probing the structure of a putative intermediate in homologous recombination: the third strand in the parallel DNA triplex is in contact with the major groove of the duplex

A three-stranded DNA that is a putative intermediate of homologous recombination is a novel DNA triplex, R-form DNA. In R-form DNA the third strand includes both purines and pyrimidines and is parallel to the identical strand of the duplex. To test and refine our previously proposed R-form base triplets we have used two approaches: (1) dimethyl sulfate protection of R-form DNA; and (2) thermal dissociation of R-form DNAs in which the duplex strands were substituted in a strand-specific manner with either 7-deaza-guanine or 7-deaza-adenine. Together, the footprinting and isosteric substitution results demonstrate that the third strand in R-form DNA is in contact with the purines in the N7 position in the major groove of the Watson-Crick duplex in three ((GC):G, (AT):A and (TA):T) out of the four possible triplets. Furthermore, these results suggest that the N7 positions of the duplex play a significant role in stabilizing the DNA-DNA contacts during the homology recognition process.

Properties of B cell stage specific and ubiquitous nuclear factors binding to immunoglobulin heavy chain gene switch regions

The Ig heavy chain (IgH) constant region (CH) class switch is manifested by DNA deletions which exchange the C mu gene of a functional VDJ-CH rearrangement for a C gamma, C epsilon or C alpha gene. Repetitive sequences (S regions) 5' of each CH gene mediate CH gene switch recombination by an illegitimate mechanism. S mu can be subdivided into S mu 5' (non-repetitive) and S mu 3' (repetitive) components with recombination occurring in either part. Here, we describe the properties of ubiquitous and B cell stage specific S mu binding factors NFS mu-U1 and NFS mu-B1 respectively. U1 only bound to S mu 5' sequences, and B1 to S mu 5', S mu 3' sequences and to other S regions with varying affinities. DMS and OP-Cu footprinting revealed the sequence AAAAAGCATGGCTGA in the U1 site while the B1 S mu 5' site overlapped the 3' end of the U1 binding site and also contained additional 3' flanking S mu repeat motifs (GAGCTGAGATGGGTGGGCT). Binding site competition assays reveal that NFS mu-B1 is either very related or identical to S alpha BP (described by Waters et al., Mol. Cell Biol. 9:5594, 1989) and BSAP (identified by Barberis et al., Genes Devl. 4:849, 1990) which were shown to bind to two sequences upstream of the S alpha repeats and within the promoters of sea urchin histone genes respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal recombination of Igh D and J gene segments in transformed pre-B cells of scid mice

Studies of Ig and TCR genes in transformed lymphocytes of scid mice have revealed aberrant DNA rearrangements. Here we present a more detailed analysis of the Igh gene recombination in nine scid pre-B cell lines transformed by Abelson murine leukemia virus. We found 85% of the rearranged Igh alleles to contain abnormal Dh-Jh deletions of varying size. All of these deletions encompassed Jh elements and extended into the Igh enhancer region, occasionally involving the switch (S) region of the C mu gene. Some of these rearrangements removed most of the Dh elements, but none appeared to extend to the Vh genes. DNA sequence analysis of the two abnormally rearranged Igh alleles in one pre-B cell line showed that no Dh or Jh coding sequences were retained at the recombination sites though heptamer-like (CACTGTG) recognition signal sequences were present in the absence of nonamer (GGTTTTTGT) recognition signal sequences. These results imply that a deregulated recombinase activity may be responsible for the abnormal Dh-Jh deletions and the absence of Vh-Dh joining in established lines of Abelson murine leukemia virus-transformed scid pre-B cells.

Abnormal recombination of Igh D and J gene segments in transformed pre-B cells of scid mice

Studies of Ig and TCR genes in transformed lymphocytes of scid mice have revealed aberrant DNA rearrangements. Here we present a more detailed analysis of the Igh gene recombination in nine scid pre-B cell lines transformed by Abelson murine leukemia virus. We found 85% of the rearranged Igh alleles to contain abnormal Dh-Jh deletions of varying size. All of these deletions encompassed Jh elements and extended into the Igh enhancer region, occasionally involving the switch (S) region of the C mu gene. Some of these rearrangements removed most of the Dh elements, but none appeared to extend to the Vh genes. DNA sequence analysis of the two abnormally rearranged Igh alleles in one pre-B cell line showed that no Dh or Jh coding sequences were retained at the recombination sites though heptamer-like (CACTGTG) recognition signal sequences were present in the absence of nonamer (GGTTTTTGT) recognition signal sequences. These results imply that a deregulated recombinase activity may be responsible for the abnormal Dh-Jh deletions and the absence of Vh-Dh joining in established lines of Abelson murine leukemia virus-transformed scid pre-B cells.

Inhibitors of poly(ADP-ribose) polymerase enhance DNA strand breaks, excision repair, and sister chromatid exchanges induced by alkylating agents

Benzamide and 3-aminobenzamide, inhibitors of poly(ADP-ribose) polymerase, synergistically enhanced the frequencies of unscheduled DNA synthesis and sister chromatid exchanges in Chinese hamster ovary (CHO) cells treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). These inhibitors also increased methyl methanesulfonate (MMS)- or MNNG-induced DNA strand breaks and significantly retarded the rejoining of strand breaks in CHO and HeLa S3 cells. These results suggest that poly(ADP-ribose) is important in the repair of DNA damage after exposure to alkylating agents and exercises a regulatory role in stabilizing chromatin structure whenever strand breaks occur in DNA.