The preparation and characterization of locust vitellogenin messenger RNA and the synthesis of its complementary DNA

Induced Accumulation of Polyubiquitin Gene Transcripts in HeLa Cells after UV-irradiation and TPA-treatment

There are three species of ubiquitin gene transcripts in HeLa cells, termed UbA (approximately 0.7 kb), UbB (approximately 1.1 kb) and UbC (approximately 2.5 kb). In the present report, the UbC transcript was shown to accumulate up to 2.5-fold after irradiation with UV light or treatment with the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA). The kinetic analysis indicated that the induced accumulation of UbC was rapid and transient; maximal accumulation of UbC was induced at 2.5 h after UV irradiation or 3 h after TPA treatment. Inhibition of a de novo protein synthesis by cycloheximide did not repress the induction of UbC after treatment with UV light and TPA. On the other hand, induction of UbA and UbB, in most cases, was not observed. UV-inducibility of human ubiquitin conjugating enzyme, E2(17k), was also tested. E2(17k) is a protein with high sequence similarity to the product of yeast DNA repair gene, RAD6. While the RAD6 gene has been reported to be inducible by UV light, no change in E2(17k) gene transcript was observed after UV irradiation.

Protein ubiquitination in the posterior silk glands of Bombyx mori

Ubiquitin gene expression and the ubiquitination of proteins in the posterior silk glands (PSG) of B. mori were analyzed developmentally with respect to fibroin synthesis and degeneration. Two ubiquitin transcripts are expressed throughout larval stages, and the level of each transcript is regulated differently. The larger transcript, a polyubiquitin mRNA, was abundant during the molt stage, while levels of the smaller ubiquitin transcript increased immediately after molting. Only a single 65 kDa ubiquitinated protein was detected late in the 5th instar, and the amount increased up to spinning stage. This ubiquitinated protein may participate in the PSG degeneration.

Highly repetitive structure and its organization of the silk fibroin gene

We have sequenced a number of cDNAs representing the Bombyx mori silk fibroin heavy chain transcript. These reveal that the central region of the fibroin gene is composed of alternate arrays of the crystalline element a and the noncrystalline element b. The core region is partitioned by a homogeneous nonrepetitive amorphous domain of around 100 bp in length. The element a is characterized by repeats of a highly conserved 18-bp sequence coding for perfect repeats of the unit peptide Gly-Ala-Gly-Ala-Gly-Ser. The element b is composed of repeats of a less-conserved 30-bp sequence which codes for a peptide similar to that in element a except in that (1) Ser is replaced by Tyr and (2) there are irregular substitutions of Ala to Val or Tyr. Therefore, the structure of the fibroin gene core consists of three-step higher-order periodicities. Heterogeneities in numbers of repeats are observed in each step of periodicity. Boundary sequence appeared in each periodicity to be quite homogeneous. Sequence analysis indicates that the unit sequences of elements a and b have homology to those of recombination hotspots reported in other genes and a recombination event may frequently occur between the misaligned sister chromatids, resulting in heterogeneities in repeat numbers and duplication or deletion of repetitive sequences. The repetitive superstructure of the fibroin gene may have been a result of continuous unequal crossovers in a primordial gene during evolution. A couple of important features of the fibroin protein were proved by the present nucleotide sequencing.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel structure of a Chinese hamster polyubiquitin gene

We isolated a polyubiquitin gene, CHUB2, from the V79 Chinese hamster genomic library, and determined its complete structure. Based on sequence homology to the human polyubiquitin gene UbC in the 5' and 3' untranslated region, the CHUB2 gene was characterized as the V79 Chinese hamster equivalent to the human UbC gene. However, the overall coding region structure of the CHUB2 gene was altered from the consensus structure of polyubiquitin genes, with the last ubiquitin coding unit being followed by 161 bp of partially deleted and mutated ubiquitin-like sequence. Although a similarly deleted and mutated polyubiquitin gene was recently reported in a partially sequenced cDNA of mouse (Finch et al. (1992) Cell Growth Differ. 3, 269-278), the present study describes the complete sequence of a polyubiquitin gene containing this unusual structure for the first time, and suggests that this structure is conserved in rodents. By employing both Southern and Northern analysis with a probe specific to the CHUB2 gene, it was found that a second, closely related gene is present in the Chinese hamster genome, and that both loci are transcriptionally active in V79 cells. The two genes, and their respective transcripts, differ in size because of variation in the relative number of repeating ubiquitin coding units.

Evolutionarily conserved structure of the 3' non-translated region of a Chinese hamster polyubiquitin gene

From a V79 Chinese hamster genomic library, we isolated a clone containing a polyubiquitin gene (designated as CHUB1), and determined its nucleotide sequence. The coding region of the CHUB1 gene consisted of five direct repeats of the ubiquitin unit with no spacer, followed by a single tyrosine residue. Northern hybridization analysis with a synthesized probe specific to the 3' non-translated region of the CHUB1 gene revealed that it codes for a 1.8 kb mRNA. An evident homology to the human polyubiquitin gene UbB and the chicken UbI gene was observed in the region corresponding to the full extent of the mature mRNA sequence, suggesting that these three genes belong to a common polyubiquitin gene subfamily, and that the sequence in the 3' non-translated region of the CHUB1 gene is unique to this subfamily.

Specific codon usage pattern and its implications on the secondary structure of silk fibroin mRNA

We have identified two distinctive regions of the repetitive unit nucleotide sequence of fibroin mRNA of Bombyx mori. The codon usage for the major amino acids, glycine, alanine and serine is distinctly different in these two regions, indicating that it is determined by the fibroin mRNA or gene structure but not by the tRNA population. Comparative computer analyses of nucleotide substitutions in the unit sequence suggest that selection has operated on the codon usage to optimize the secondary structure characteristic of the fibroin mRNA.

Vitellogenin gene expression in male rainbow trout (Salmo gairdneri)

Estrogen has a marked effect on the expression of vitellogenin, the egg yolk precursor protein in the liver of egg-laying vertebrates. cDNA clones specific for trout vitellogenin mRNA have been used to study the expression of the vitellogenin genes in rainbow trout (Salmo gairdneri). The steady-state levels of vitellogenin mRNA in the liver of male rainbow trout were measured during primary and secondary stimulation with estradiol. The kinetics of induction in trout appear to be very similar to those seen in Xenopus and chicken in that a lag of approximately 2 days is observed in the accumulation of serum vitellogenin during primary induction. This lag is not observed during the secondary stimulation. The primary induction of vitellogenin mRNA in trout liver, using a single injection of estradiol (3 mg/kg body wt) results in a short-lived rise, reaching a maximum level of 260 ppm total RNA on Day 2. Using silastic implants of estradiol to induce a primary response produces a large increase in the steady-state level of vitellogenin mRNA which reaches a maximum of 2750 ppm total RNA on Day 10. During secondary stimulation, using silastic tubing the maximum level reached was 1200 ppm of the total RNA on Day 7, approximately half the level seen in the primary induction using the silastic implants. The difference in these two levels is due to an increase in the steady-state levels of rRNA, which appear to increase between Days 10 and 21 after the primary stimulation. These results demonstrate that the induction of vitellogenesis in the trout by estradiol involves changes in the steady-state levels of a number of different mRNA and rRNA sequences and resembles that seen in Xenopus and chicken.

Cloning and 5' end nucleotide sequences of two juvenile hormone-inducible vitellogenin genes of the African migratory locust

Screening of lambda libraries prepared with locust (Locusta migratoria) genomic DNA yielded overlapping clones containing two complete vitellogenin genes, designated A and B, along with extensive 3'- and 5'-flanking sequences. Genes A and B are about 12 kb and 10.5 kb long, respectively, and both hybridize on Northern blots with 6300-nucleotide RNAs previously identified as vitellogenin mRNAs. Each gene contains a large intron near the 5' end and must also contain other introns. Repetitive "Lm1 elements," similar to the human Alu repetitive DNA elements, and other repeated sequences occur within the large intron and in the 3'- and 5'-flanking regions of each gene. Southern blots showed no cross-hybridization between the major portions of mRNA-coding sequences of genes A and B. DNA sequences have been determined for the 5' terminal exons and flanking regions of both genes. Both genes contain short (56-58 nucleotide) 5' leader exons, which, unlike the rest of the coding region, are highly conserved in sequence (87% identical) and code for amino acids that resemble the amino-terminal sequences of vertebrate vitellogenins. The upstream 5'-flanking sequences of the two genes contain several short stretches of similarity that may be involved in juvenile hormone regulated expression.

Identification of a nonhistone chromosomal protein associated with heterochromatin in Drosophila melanogaster and its gene

Monoclonal antibodies were prepared against a fraction of nuclear proteins of Drosophila melanogaster identified as tightly binding to DNA. Four of these antibodies were directed against a 19-kilodalton nuclear protein; immunofluorescence staining of the polytene chromosomes localized the antigen to the alpha, beta, and intercalary heterochromatic regions. Screening of a lambda gt11 cDNA expression library with one of the monoclonal antibodies identified a recombinant DNA phage clone that produced a fusion protein immunologically similar to the heterochromatin-associated protein. Polyclonal sera directed against the bacterial lacZ fusion protein recognized the same nuclear protein on Western blots. A full-length cDNA clone was isolated from a lambda gt10 library, and its DNA sequence was obtained. Analysis of the open reading frame revealed an 18,101-dalton protein encoded by this cDNA. Two overlapping genomic DNA clones were isolated from a Charon 4 library of D. melanogaster with the cDNA clone, and a restriction map was obtained. In situ hybridization with these probes indicated that the gene maps to a single chromosome location at 29A on the 2L chromosome. This general strategy should be effective for cloning the genes and identifying the genetic loci of chromosomal proteins which cannot be readily assayed by other means.

Identification of a nonhistone chromosomal protein associated with heterochromatin in Drosophila melanogaster and its gene

Monoclonal antibodies were prepared against a fraction of nuclear proteins of Drosophila melanogaster identified as tightly binding to DNA. Four of these antibodies were directed against a 19-kilodalton nuclear protein; immunofluorescence staining of the polytene chromosomes localized the antigen to the alpha, beta, and intercalary heterochromatic regions. Screening of a lambda gt11 cDNA expression library with one of the monoclonal antibodies identified a recombinant DNA phage clone that produced a fusion protein immunologically similar to the heterochromatin-associated protein. Polyclonal sera directed against the bacterial lacZ fusion protein recognized the same nuclear protein on Western blots. A full-length cDNA clone was isolated from a lambda gt10 library, and its DNA sequence was obtained. Analysis of the open reading frame revealed an 18,101-dalton protein encoded by this cDNA. Two overlapping genomic DNA clones were isolated from a Charon 4 library of D. melanogaster with the cDNA clone, and a restriction map was obtained. In situ hybridization with these probes indicated that the gene maps to a single chromosome location at 29A on the 2L chromosome. This general strategy should be effective for cloning the genes and identifying the genetic loci of chromosomal proteins which cannot be readily assayed by other means.

Ubiquitin is a heat shock protein in chicken embryo fibroblasts

Clones containing heat-inducible mRNA sequences were selected from a cDNA library prepared from polyadenylated RNA isolated from heat-shocked chicken embryo fibroblasts. One recombinant DNA clone, designated clone 7, hybridized to a 1.2-kilobase RNA that was present in normal cells and increased fivefold during heat shock. Clone 7 also hybridized to an RNA species of 1.7 kilobases that was present exclusively in heat-shocked cells. In vitro translation of mRNA hybrid selected from clone 7 produced a protein product with a molecular weight of approximately 8,000. Increased synthesis of a protein of similar size was detected in chicken embryo fibroblasts after heat shock. DNA sequence analysis of clone 7 indicated its protein product has amino acid sequences identical to bovine ubiquitin. In addition, clone 7 contains tandem copies of the ubiquitin sequences contiguous to each other with no untranslated sequences between them. We discuss some possible roles for ubiquitin in the heat shock response.

Ubiquitin is a heat shock protein in chicken embryo fibroblasts

Clones containing heat-inducible mRNA sequences were selected from a cDNA library prepared from polyadenylated RNA isolated from heat-shocked chicken embryo fibroblasts. One recombinant DNA clone, designated clone 7, hybridized to a 1.2-kilobase RNA that was present in normal cells and increased fivefold during heat shock. Clone 7 also hybridized to an RNA species of 1.7 kilobases that was present exclusively in heat-shocked cells. In vitro translation of mRNA hybrid selected from clone 7 produced a protein product with a molecular weight of approximately 8,000. Increased synthesis of a protein of similar size was detected in chicken embryo fibroblasts after heat shock. DNA sequence analysis of clone 7 indicated its protein product has amino acid sequences identical to bovine ubiquitin. In addition, clone 7 contains tandem copies of the ubiquitin sequences contiguous to each other with no untranslated sequences between them. We discuss some possible roles for ubiquitin in the heat shock response.

rDNA in Locusta migratoria is very variable: two introns and extensive restriction site polymorphisms in the spacer

Cloned ribosomal DNA (rDNA) of Locusta migratoria was analyzed by restriction site mapping and SI nuclease experiments. The repeat unit is 18 kb long. The nontranscribed spacer region (NTS) is very large (11 kb) and homogeneous in length, but many of the restriction sites are heterogeneous among the repeat units. Two introns of different length were found at different positions in the 28S gene. They are present in less than 5% of the genes.

The preparation and characterization of vitellogenin messenger RNA from rainbow trout (Salmo gairdneri)

Agarose-gel electrophoresis of polyadenylated RNA from livers of oestrogen-treated male rainbow trout revealed a major high-Mr species (7200 nucleotides), which is absent from the polyadenylated RNA isolated from hormonally unstimulated male trout liver. Translation in vitro of the RNA from oestrogen-treated males in a mRNA-dependent rabbit reticulocyte lysate produced a protein (Mr 200 000) that could be immunoprecipitated with antibodies against trout serum vitellogenin, but no immunoprecipitable protein was synthesized with RNA from control animals. DNA complementary to the RNA from oestrogen-stimulated and control male trout liver was synthesized and back-hybridized, with R0t1/2 of 3.8 X 10(-2) and 1 X 10(-1) mol X litre-1 X s for RNA from hormone-treated and control animals respectively. The 9% increase in the abundant mRNA after oestrogen stimulation is due to the induction of vitellogenin mRNA.

Prekeratin biosynthesis in human scalp epidermis

Analysis of human scalp epidermal prekeratin polypeptides by two-dimensional gel electrophoresis revealed that each of the bands observed in one-dimensional electrophoresis consisted of three to five polypeptides of the same molecular weight but differing in isoelectric points. It was possible to divide the polypeptides into two families, with isoelectric points in the ranges pH 6.0-8.0 and pH 5.0-5.5 respectively. Incorporation of radiolabelled amino acids into freshly excised pieces of scalp epidermis showed that some of the polypeptides had relatively greater contents of glycine and serine than others. Radiolabelled methionine and leucine were, in contrast, incorporated more or less uniformly into all the polypeptides. After incubation with 32P-labelled orthophosphate, relatively more intense labelling by 32P was observed in the higher molecular weight bands of each family. The most basic of the isoelectric variants in each case did not take up phosphate, implying that at least some of the variation in charge was due to different degrees of phosphorylation. Polyadenylated RNA isolated from scalp epidermis was translated in an RNA-dependent reticulocyte haemolysate system followed by immunoprecipitation and electrophoresis. The polypeptides isolated by using anti-(human scalp prekeratin) immunoglobulin G had similar electrophoretic mobilities in sodium dodecyl sulphate/polyacrylamide gels to authentic prekeratin polypeptides, but had different isoelectric properties. This suggested that the products of keratin gene expression undergo post-translational modification.

Construction and partial characterization of a recombinant DNA probe for locust vitellogenin messenger RNA

Double-stranded DNA complementary to poly(A)-containing RNA from the fat body of adult female locusts, Locusta migratoria, was synthesized. Hybrid molecules containing this cDNA was constructed in the PstI site of the plasmid pAT 153 by the technique of dC . dG tailing and amplified in Escherichia coli K-12 strain HB 101. Ten colonies of bacteria were identified as carrying recombinant plasmids containing DNA complementary to locust vitellogenin mRNA by (a) 'Northern' blot hybridization analysis and (b) hybrid selection of vitellogenin mRNA and immunological detection of the products of translation of the mRNA. Of the ten recombinant plasmids, one, termed plasmid 4E, containing a cDNA insert of about 650 nucleotides, was characterized in greater detail and a partial restriction map obtained. Using this hybrid plasmid it was possible to derive a value for the average content of vitellogenin mRNA in the adult female locust fat body as 1.5 x 10(5) molecules/cell, and to establish that the haploid genome of L. migratoria contains only one or two genes coding for vitellogenin.

The extraction, characterization and in vitro translation of RNA from adult Schistosoma mansoni

We have extracted RNA from Schistosoma mansoni using the lithium chloride-urea method which gives good yields of undegraded RNA. The results of agarose gel electrophoresis of RNA extracted by this procedure suggest that S. mansoni has an in vivo nick in the large rRNA sub-unit. Translation of the RNA in a rabbit reticulocyte lysate gave significant incorporation of [35S]methionine into synthesized proteins. Immunoprecipitation of these translation products using a hyperimmune monkey serum sedimented between 5 and 8% of the radioactivity, which appeared to be present in approximately 13 proteins of molecular weights 18, 20, 21, 22, 23, 35, 40, 54, 60, 70, 74, 78 and 105 K Daltons.

Evolutionary conservation of vitellogenin genes

Homologous and heterologous hybridizations in solution were performed between sheared genomic DNA and DNA complementary to vitellogenin mRNA of Xenopus, chicken, and migratory locust. The kinetics of hybridization and the thermal stability of the hybrids formed suggested a high degree of conservation of coding sequences of insect, amphibian, and avian vitellogenin genes. These cDNA probes hybridized to calf thymus DNA to a slight, but significant, extent, and not at all to Micrococcus lysodektikus DNA. DNA complementary to Xenopus albumin mRNA did not cross-hybridize significantly with locust or chicken DNA. Further evidence for the evolutionary conservation of vitellogenin genes was obtained from Southern blot analysis of restriction endonuclease-digested genomic DNA from a variety of vertebrate and invertebrate oviparous animals (Xenopus, chicken, migratory and desert locusts, yellow meal worm, carab moth, and Mediterranean fruitfly). When probed with cloned vitellogenin cDNAs from Xenopus and migratory locust, the DNA of these organisms showed varying degrees of homology of parts of the vitellogenin coding sequences. Southern blot analysis also showed that a part of the sequence specified in the cloned Xenopus vitellogenin cDNA was represented as repetitive DNA in the locust genome. However, cloned locust vitellogenin cDNA hybridized to discrete fragments of the restricted vertebrate DNA. These studies demonstrate a remarkably high degree of conservation of insect, amphibian, and avian vitellogenin genes.