Microarray analysis of gene expression profiles in wing discs of Bombyx mori during pupal ecdysis

Wing discs of holometabolous insects undergo dramatic morphological changes during metamorphosis, a process that is controlled by the actions of hundreds of gene products. Using cDNA microarrays constructed from 5086 ESTs, we monitored the gene expression profiles in wing discs of Bombyx mori at 13 time points during pupal ecdysis (day-4 fifth instar larvae to day-0 pupae). Of the 5086 ESTs on the microarrays, 2998 ESTs had significant signals in more than half of the experiments. Of the 2998 ESTs, genes represented by 683 ESTs showed significant perturbations during pupal ecdysis. Genes previously known to be induced during metamorphosis were identified, including E75, Urbain, Chitinases, and cuticle proteins. The expressions of genes represented by 59 ESTs induced at the beginning of wandering contained genes predicted to be involved in protein degradation, amino acid metabolism, and amino acid transport. The expressions of genes represented by 147 ESTs induced after the ecdysteroid peak had a role in cuticle synthesis, pigmentation, ion transport, protein transport, and transcription regulation. The expressions of genes represented by 85 ESTs repressed after the ecdysteroid peak were predicted to be involved in nucleotide and nucleic acid metabolism and cell cycle. This indicates the involvement of several biological processes in wing disc development during metamorphosis.

A medaka gene map: the trace of ancestral vertebrate proto-chromosomes revealed by comparative gene mapping

The mapping of Hox clusters and many duplicated genes in zebrafish indicated an extra whole-genome duplication in ray-fined fish. However, to reconstruct the preduplication chromosomes (proto-chromosomes), the comparative genomic studies of more distantly related teleosts are essential. Medaka and zebrafish are ideal for this purpose, because their lineages separated from their last common ancestor approximately 140 million years ago. To reconstruct ancient vertebrate chromosomes, including the chromosomes of the vertebrate ancestor of humans from 450 million years ago, we mapped 818 genes and expressed sequence tags (ESTs) on a single meiotic backcross panel obtained from inbred strains of the medaka, Oryzias latipes. Comparisons of linkage relationships of orthologous genes among three species of vertebrates (medaka, zebrafish, and human) indicate the number and content of the chromosomes of the last common ancestor of ray-fined fish and lobe-fined fish (including humans), and the extra whole genome duplication event in the ray-fin lineage occurred in the common ancestor of perhaps all teleosts.

Characterization and transcriptional profiles of three Spodoptera frugiperda genes encoding cysteine-rich peptides. A new class of defensin-like genes from lepidopteran insects?

The present work describes sequence and transcription of three Spodoptera frugiperda genes encoding 6-cysteine-rich peptides. Sequence alignments indicate that the predicted peptides belong to the insect defensin family, although phylogenetic analyses suggest they form a cluster distinct from that of other neopteran insect defensins. The three genes were identified in a non-immune-challenged Sf9 cells cDNA (DNA complementary to RNA) library (Landais et al., Bioinformatics, in press) and were named spodoptericin, Sf-gallerimycin and Sf-cobatoxin. Spodoptericin is a novel defensin-like gene that appears to be weakly up-regulated following injection of bacteria and fungi. Interestingly, no sequence motif clearly homologous to cis regulatory element involved in the regulation of antimicrobial genes was found. An homologue of the spodoptericin gene was identified in the SilkBase Bombyx mori cDNA library. Sf-gallerimycin is related to the Galleria mellonella gallerimycin gene and is induced after immune challenge by injection of bacteria in the larval fat body as well as in hemocytes. In silico analysis of the sequence upstream from the cDNA reveals the presence of at least one motif homologous to a nuclear factor kappaB (NF-kappaB) binding site. Finally, Sf-cobatoxin is related to the G. mellonella cobatoxin-like gene. Despite high levels of constitutive expression compared to the two previous genes, transcription of Sf-cobatoxin is increased after immune, in particular, bacterial challenge. We therefore confirm that these three genes encode potential candidate molecules involved in S. frugiperda innate humoral response.

The construction of an EST database for Bombyx mori and its application

To build a foundation for the complete genome analysis of Bombyx mori, we have constructed an EST database. Because gene expression patterns deeply depend on tissues as well as developmental stages, we analyzed many cDNA libraries prepared from various tissues and different developmental stages to cover the entire set of Bombyx genes. So far, the Bombyx EST database contains 35,000 ESTs from 36 cDNA libraries, which are grouped into approximately 11,000 nonredundant ESTs with the average length of 1.25 kb. The comparison with FlyBase suggests that the present EST database, SilkBase, covers >55% of all genes of Bombyx. The fraction of library-specific ESTs in each cDNA library indicates that we have not yet reached saturation, showing the validity of our strategy for constructing an EST database to cover all genes. To tackle the coming saturation problem, we have checked two methods, subtraction and normalization, to increase coverage and decrease the number of housekeeping genes, resulting in a 5-11% increase of library-specific ESTs. The identification of a number of genes and comprehensive cloning of gene families have already emerged from the SilkBase search. Direct links of SilkBase with FlyBase and WormBase provide ready identification of candidate Lepidoptera-specific genes.

A Bombyx mori gene, BmChi-h, encodes a protein homologous to bacterial and baculovirus chitinases

We have cloned and characterized a novel chitinase gene (BmChi-h) from the silkworm, Bombyx mori. BmChi-h cDNA has an open reading frame of 1,665 nucleotides, encoding a protein of 555 amino acid residues. The predicted protein shared extensive similarities with bacterial and baculovirus chitinases in both amino acid sequences (73% identity with Serratia marcescens chiA and 63% with Autographa californica nucleopolyhedrovirus chiA) and domain architectures. BmChi-h was a single-copy gene and located on chromosome 7. The expression of BmChi-h mRNA was observed in a stage- and tissue-specific manner that was almost identical to that of another chitinase gene previously cloned from B. mori. We further determined the overall genomic organization of BmChi-h. There was no intron in the ORF of BmChi-h. However, BmChi-h was transcribed from three promoters, which generated three isoforms in the 5'-UTR of the transcript. Phylogenetic analysis suggested that ancestral species of B. mori acquired the chitinase gene from a bacterium or an ancestral baculovirus via horizontal gene transfer.

W-derived BAC probes as a new tool for identification of the W chromosome and its aberrations in Bombyx mori

We isolated four W chromosome-derived bacterial artificial chromosome (W-BAC) clones from Bombyx mori BAC libraries by the polymerase chain reaction and used them as probes for fluorescence in situ hybridization (FISH) on chromosome preparations from B. mori females. All four W-BAC probes surprisingly highlighted the whole wild-type W sex chromosome and also identified the entire original W-chromosomal region in W chromosome-autosome translocation mutants. This is the first successful identification of a single chromosome by means of BAC-FISH in species with holokinetic chromosomes. Genomic in situ hybridization (GISH) by using female-derived genomic probes highlighted the W chromosome in a similar chromosome-painting manner. Besides the W, hybridization signals of W-BAC probes also occurred in telomeric and/or subtelomeric regions of the autosomes. These signals coincided well with those of female genomic probes except one additional GISH signal that was observed in a large heterochromatin block of one autosome pair. Our results support the opinion that the B. mori W chromosome accumulated transposable elements and other repetitive sequences that also occur, but scattered, elsewhere in the respective genome.

Isolation and comparison of different ecdysone-responsive cuticle protein genes in wing discs of Bombyx mori

Microarray analysis was used to isolate an ecdysone up-regulated cuticle protein gene from wing discs of Bombyx mori. Transcripts of isolated cDNAs were identified by Northern blot analysis. Expression of the BMWCP10 gene was observed during the W0-W3 stages with the strongest signal being at the W2 stage. In contrast, expression of the BMWCP2 gene was observed at the W3and P0 stages. Expression of BMWCP10 was identified after exposure to 20E in vitro, while that of BMWCP2 was identified after exposure to 20E followed by its removal. Induction of BMWCP10 by 20E was observed in 30 min and was not inhibited by cycloheximide. Expression of BMWCP2 was observed in wing discs cultured for more than 18 h in a hormone-free medium after 20E removal. At least 4 h exposure to 20E was required before removal for induction of BMWCP2. Induction of BMWCP2 required protein synthesis. Thus, different ecdysone-responsive cuticle protein genes in wing discs of Bombyx mori were isolated.

Genomic sequence of a 320-kb segment of the Z chromosome of Bombyx mori containing a kettin ortholog

The sex chromosome constitution of the silkworm, Bombyx mori, is ZW in the female and ZZ in the male. Very little molecular information is available about the Z chromosome in Lepidoptera, although the topic is interesting because of the absence of gene dosage compensation in this chromosome. We constructed a 320-kb BAC contig around the Bmkettin gene on the Z chromosome in Bombyx and determined its nucleotide sequence by the shotgun method. We found 13 novel protein-coding sequences in addition to Bmkettin. All the transposable elements detected in the region were truncated, and no LTR retrotransposons were found, in stark contrast to the situation on the W chromosome. In this 320-kb region, four genes for muscle proteins (Bmkettin, Bmtitin1, Bmtitin2, and Bmprojectin) are clustered, together with another gene (Bmmiple) on the Z chromosome in B. mori; their orthologs are also closely linked on chromosome 3 in Drosophila, suggesting a partial synteny. Real-time RT-PCR experiments demonstrated that transcripts of 13 genes of the 14 Z-linked genes found accumulated in larger amounts in males than in female moths, indicating the absence of gene dosage compensation. The implications of these findings for the evolution and function of the Z chromosome in Lepidoptera are discussed.

Reliability of the mechanomyogram detected with an accelerometer during voluntary contractions

The accelerometer is used for mechanomyogram (MMG) recordings of muscle contractions. Although the mechanical characteristics of other MMG transducers have been determined with reference to the accelerometer, mechanical aspects of the accelerometer itself, including the weight of the transducer, have not been verified. This study was designed to reinvestigate the mechanical variable of the MMG signal detected with an accelerometer, with reference to a laser distance sensor (LDS), and then to clarify the influence of the accelerometer weight on the MMG recording during muscle contractions. The study was performed during mechanical sinusoidal vibrations and during voluntary contractions of the quadriceps muscle. Maximum differences in the amplitude spectral density functions between the LDS signal and the double integral of the accelerometer signal were approximately 4 microm. The results verified that the MMG signal from the accelerometer accurately reflected the acceleration of body surface vibration. However, the MMG signal was gradually distorted when weight was added to the accelerometer: the addition of 4.0 g (total 6.0 g, including 2.0 g of accelerometer) substantially attenuated the MMG signal. The results suggest that the appropriate weight for the accelerometer should be less than 5.0 g for measurements of the quadriceps muscle and indicate that the transducer weight must be taken into account for accurate measurement of muscles of different sizes.

Analysis of alpha- and beta-tubulin genes of Bombyx mori using an EST database

Tubulin is one of the most widespread classes of multiprotein families and is well known to construct microtubules with two different subunits, alpha- and beta-tubulin. In the course of genome analysis of Bombyx mori, we have constructed an EST database by large-scale sequencing of clones that were randomly selected from cDNA libraries of various tissues and organs belonging to different developmental stages. Using this EST database, we have identified four types of beta-tubulin gene and three types of alpha-tubulin gene. Based on the analysis of deduced amino acid sequences, we have determined the phylogenetic relationships of tubulins between Bombyx and Drosophila melanogaster as well as two other moth species, suggesting that each tubulin is classified into at least three distinct subfamilies: a ubiquitously expressed one, a developmentally regulated one and a testis specific one.

Functional characterization of the human spermidine/spermine N(1)-acetyltransferase gene promoter

Spermidine/spermine N(1)-acetyltransferase (SSAT), the key enzyme of polyamine catabolism, is induced by antiproliferative stresses. We analyzed the 5' flanking region of the human SSAT gene, and clarified that the binding of Sp1 to the GC-box located 42 to 51 bp upstream from the transcription start site is essential for transcription in HeLa S3 cells. A polyamine-responsive element (PRE) seemed to be responsible for the elevated transcription after X-ray irradiation.

Nested retrotransposons on the W chromosome of the wild silkworm Bombyx mandarina

The W chromosome of the silkworms Bombyx mori or B. mandarina is recombinationally isolated from the Z chromosome and the autosomes. We previously characterized a female-specific randomly amplified polymorphic DNA (RAPD), designated W-Yamato, derived from the W chromosome of the wild silkworm Bombyx mandarina. To further analyse the W chromosome of B. mandarina, we obtained a lambda phage clone that contains the W-Yamato RAPD sequence and sequenced the 16.7 kb DNA insert. We found that this DNA comprises a nested structure of at least seven elements: six retrotransposons and one transposable element-like sequence. The transposable element-like sequence is inserted into a micropia-like retrotransposon (Karate). The Karate and the non-long terminal repeat (non-LTR) retrotransposon BMC1 are inserted into a 412-like retrotransposon (Judo). Furthermore, this Judo, and two non-LTR retrotransposons (Kurosawa and Kendo) are inserted into a Pao-like retrotransposon (Yamato). These results indicate that the retrotransposons inserted into the W chromosome are not efficiently removed but accumulate gradually as strata without recombination.

Exercise intensity based on heart rate while walking in spastic cerebral palsy

We examined the heart rate (HR) of subjects with spastic cerebral palsy (CP) in order to estimate exercise intensity while walking. The subjects were 17 subjects with CP (14.0 +/- 3.7 years of age) containing 7 subjects rated as level 1, 4 subjects rated as level 2, and 6 subjects rated as level 3 by the Gross Motor Function Classification System, and 7 normal subjects (12.4 +/- 2.8 years of age) were used as a controls. Even in subjects whose gross motor function was excellent (rated as level 1), the HR significantly increased while walking when compared to normal subjects (p < 0.05), although the walking speed between the groups was not different. According to the HR, the exercise intensity while walking was adapted from weakly to moderately and thought to be appropriate for exercise. On the other hand, walking speed was significantly reduced in the subjects rated as level 2 and 3 (p < 0.05), and the HR increased significantly (p < 0.05). Seven of the ten subjects rated as either level 2 or 3 showed a high HR of over 150 beats/min while walking. The HR while walking of the two subjects rated as level 3 continued to increase although the walking speed was kept constant. The walking exercise would be too strong and become detrimental to such subjects.

Spectrum of Znfn1a1 (Ikaros) inactivation and its association with loss of heterozygosity in radiogenic T-cell lymphomas in susceptible B6C3F1 mice

Ikaros (now known as Znfn1a1), a Krüppel-type zinc-finger transcription factor that plays a critical role in both lineage commitment and differentiation of lymphoid cells, has recently been shown to function as a tumor suppressor gene. We have previously reported a high frequency of LOH (approximately 50%) at the Znfn1a1 locus in radiation-induced T-cell lymphoma in susceptible B6C3F1 mice. The aim of the present study was to delineate the types of Znfn1a1 inactivation, with special reference to the LOH status, and to determine the relative contribution of each type of Znfn1a1 inactivation in radiation-induced T-cell lymphomas in B6C3F1 mice. We demonstrated that Znfn1a1 was frequently altered (in approximately 50% of T-cell lymphomas), and that its inactivation was caused by a variety of mechanisms, which came under one of the following four categories: (1) null expression (14%); (2) expression of unusual dominant-negative isoforms (11%); (3) amino acid substitutions in the N-terminal zinc-finger domain for DNA binding caused by point mutations (22%); (4) lack of the Znfn1a1 isoform 1 due to the creation of a stop codon by insertion of a dinucleotide in exon 3 (3%). The null expression, amino acid substitutions, and dinucleotide insertion inactivation types were well correlated with LOH at the Znfn1a1 allele (86%) and were consistent with Knudson's two-hit theory. On the other hand, T-cell lymphomas expressing dominant-negative Znfn1a1 isoforms retained both alleles. These results indicate that Znfn1a1 inactivation takes place by a variety of mechanisms in radiation-induced murine T-cell lymphomas and is frequently associated with LOH, this association depending on the type of inactivation.

Characterization of the kynurenine 3-monooxygenase gene corresponding to the white egg 1 mutant in the silkworm Bombyx mori

Kynurenine 3-monooxygenase (KMO, EC 1.14.13.9), which catalyzes the oxidation of kynurenine to 3-hydroxykynurenine, is involved in the synthesis of ommochrome pigments in insects. A silkworm mutant, white egg 1 ( w-1), has been shown to be deficient in this enzyme activity. The mutant is characterized morphologically by its white eyes and the fact that the females lay white eggs. To analyze the relationship between the KMO gene and the mutation, we first determined the entire sequence of a full-length 2.0-kb cDNA and examined its expression pattern in the wild type. The cDNA sequence contains one ORF encoding a polypeptide of 456 amino acids, and transcripts were detected in the larval Malpighian tubules and the pupal ovaries, but not in other tissues. Southern analysis and nucleotide sequencing showed that the KMO gene is present in a single copy and consists of ten exons distributed over a 16-kb region. Comparison of the transcripts between the wild type and mutant silkworms showed that the wild type expressed a single transcript, whereas the mutant exhibited markedly reduced amounts of two transcripts with sizes of 2.0 kb and 1.8 kb. Nucleotide sequence analysis of these mutant transcripts indicated that sequences corresponding to the ninth and tenth exons were missing. Inverse PCR and Southern analysis of the mutant gene demonstrated that the corresponding genomic region was deleted in the w-1 mutant.

Disruption of Xpg increases spontaneous mutation frequency, particularly A:T to C:G transversion

Cells isolated from Xpg (the mouse counterpart of XPG)-disrupted mice underwent premature senescence and showed early onset of immortalization, suggesting that Xpg might be involved in genetic stability. Recent studies showed that human XPG, in addition to its function in the nucleotide excision repair (NER), was involved in the repair of oxidative base damages such as thymine glycol (Tg) and 8-oxo-guanine (8-oxoG), and this may explain the genetic instability observed in Xpg-deficient cells. To clarify this point, we determined spontaneous mutation frequencies and the type of spontaneous base substitution mutations in cells obtained from normal and Xpg-deficient mice using the supF shuttle vector (pNY200) for mutation assay. The spontaneous mutation frequency of the supF gene in pNY200 propagated in the Xpg-deficient cells was about three times higher than that in normal cells, indicating the importance of Xpg in reducing the frequency of spontaneous mutations. The frequency of spontaneous base substitution mutations at A:T sites, particularly that of the A:T to C:G transversion, increased markedly in the Xpg-deficient cells.

The mechanism of sex-specific splicing at the doublesex gene is different between Drosophila melanogaster and Bombyx mori

We have previously reported that Bmdsx, a homologue of the sex-determining gene, doublesex (dsx), was found to be sex-specifically expressed in various tissues at larval, pupal, and adult stages in the silkworm, Bombyx mori, and was alternatively spliced to yield male- and female-specific mRNAs. To reveal sex-specific differences in splicing patterns of Bmdsx pre-mRNA, the genomic sequence was determined and compared with male- and female-specific Bmdsx cDNA sequences. The open reading frame (ORF) consisted of five exons. Exons 3 and 4 were specifically incorporated into the female type of Bmdsx mRNA. On the other hand, exon 2 was spliced to exon 5 to produce the male type mRNA of Bmdsx. As in the case of Drosophila dsx, the OD2 domain was separated by a female-specific intron into sex-independent and sex-dependent regions. Sex-specific splicing occurred in equivalent positions in the Drosophila dsx gene. However, unlike Drosophila dsx, the female-specific introns showed no weak 3' splice sites, and the TRA/TRA-2 binding site related sequences were not found in the female-specific exon, nor even in any other regions of the Bmdsx gene. Moreover, an in vitro splicing reaction consisting of HeLa cell nuclear extracts showed that the female-type of Bmdsx mRNA represented the default splicing. These findings suggest that the structural features of the sex-specific splicing patterns of Bmdsx pre-mRNA are similar to those of Drosophila dsx but the regulation of sex-specific alternative splicing of Bmdsx pre-mRNA is different.

Isolation and expression of an ecdysteroid-inducible neutral endopeptidase 24.11-like gene in wing discs of Bombyx mori

In the process of comparison of two cDNA libraries (W0, W2), we isolated a clone from the wing discs of Bombyx mori encoding a putative neutral endopeptidase 24.11-like gene. The predicted open reading frame encoded 772 amino acid residues, having about 53% identity with Drosophila GH07643, 36% with rat NEP, and 34% with rat ECE. This is the first NEP gene isolated in invertebrate. A 3.6-kb transcript was found to accumulate in the wing disc according to the increase of ecdysteroid titer during metamorphosis. Accumulation of the transcript was induced in wing discs with 20-hydroxyecdysone about 20h after incubation, which was inhibited by cycloheximide. This gene is ecdysone-inducible, appears to encode a functional protein, and may function during wing metamorphosis.

Identification of four small molecular mass proteins in the silk of Bombyx mori

This paper describes cDNAs of four small-size proteins that occur in the cocoon silk of Bombyxmori. Two of them (9.9 and 10.3 kDa), which have the N-terminal sequences and the spacing of a few amino acids at C-termini similar to the seroin of Galleria mellonella, are called seroin 1 and seroin 2. The corresponding genes are expressed in the middle, and to a small extent also in the posterior silk gland sections. The seroin 1 and less conspicuously the seroin 2 mRNAs accumulate in the course of the last larval instar to a maximum in postspinning larvae. Two other proteins (6 kDa and 4.7 kDa) of B. mori cocoons were identified as a typical Kunitz-type and a somewhat unusual Kazal-type proteinase inhibitors, and named BmSPI 1 and BmSPI 2, respectively. Their genes are expressed in the middle, and the BmSPI 1 gene slightly also in the posterior silk gland sections. The expression ensues a few days after the last larval ecdysis and increases until the cocoon spinning. Post-spinning larvae still contain high amounts of the BmSPI 1 but no BmSPI 2 transcripts. It is assumed that seroins and proteinase inhibitors are involved in cocoon protection against predators and microbes.

Reduced sensitivity to and ras mutation spectrum of N-ethyl-N-nitrosourea-induced thymic lymphomas in adult C.B-17 scid mice

Scid mice are defective in the ability to repair DNA double strand breaks and, as a consequence, their cells are radiosensitive. Further, they have been shown to be prone to develop thymic lymphomas (TLs) after small doses of ionizing radiation. Little is known, however, on the role of scid mutation in chemical carcinogenesis. To determine if scid mutation increased predisposition to chemical carcinogenesis, we examined both the susceptibility of scid mice to N-ethyl-N-nitrosourea (ENU)-induced lymphomagenesis and the involvement of ras gene activation. Adult female mice at 8 weeks of age were given ENU in their drinking water at 400 ppm for 2-10 weeks. Contrary to expectations, we observed a two to three-fold reduction in TL development in the scid mice. The highest incidence was achieved by ENU treatment for 8 weeks for scid and wild-type C.B-17 mice, of 42 and 85%, respectively (P<0.05). We investigated whether this was attributable to the usage of the ras mutation pathway. There was, however, no significant difference in the frequency and spectrum of K-ras mutation between the scid and wild-type C.B-17 mice. Most of the K-ras mutations were either GGT to GAT transition in codon 12 (11/23: 48%) or CAA to CCA transversion in codon 61 (8/23: 35%) that was independent of scid background. The incidence of N-ras mutation was very low. These results indicate that scid mice are less susceptible to ENU-induced lymphomagenesis and ras gene mutation frequently occurs in both scid and wild-type C.B-17 mice.

Williams syndrome and deficiency in visuospatial recognition

This study aimed to assess the visuospatial abilities of five children with Williams syndrome (four males aged 9 years 3 months, 7 years 11 months, 8 years 1 month, and 10 years 8 months respectively, and one female aged 6 years 3 months). First, the children's visuospatial abilities were examined by asking them to copy a figure. Second, their cognitive processing abilities were assessed using the Japanese Kaufman Assessment Battery for Children. This test was used because it is an objective one, standardized in Japan, and is a measure of fluid ability including spatial localization. Participants scored significantly low on the spatial memory subtest indicating that there was a deficit in spatial localization. Children's performance in line copying tasks improved when the dots were in colour. Results suggest a deficit in the dorsal stream of visual cognition, with a relatively preserved ventral stream.

Mass isolation of cuticle protein cDNAs from wing discs of Bombyx mori and their characterizations

Multiple cloning of cuticle protein genes was performed by sequencing of cDNAs randomly selected from a cDNA library of wing discs just before pupation, and nine different cuticular protein genes were identified. Thirty-one clones of a cuticle protein gene were identified from the 1050 randomly sequenced clones; about 3% were cuticle protein genes in the W3-stage wing disc cDNA library. The sequence diversity of the deduced amino acid sequences of isolated Bombyx cuticle genes was examined along with the expression profiles. The deduced amino acid sequences of the nine cuticle protein genes contained a putative signal peptide at the N-terminal region and a very conserved hydrophilic region known as the R and R motif. The developmental expression of cuticle genes was classified into two types: pupation (five clones were expressed only around pupation) and pupation and mid-pupal (four clones were expressed around this stage). All the isolated genes were expressed in the head, thoracic, and abdominal regions of the epidermis at different levels around pupation, but no expression was observed in the epidermis at the fourth molting stage.

A mutation in the largest (catalytic) subunit of RNA polymerase II and its relation to the arrest of the cell cycle in G(1) phase

Transcriptional activity of RNA polymerase II is modulated during the cell cycle. We previously identified a temperature-sensitive mutation in the largest (catalytic) subunit of RNA polymerase II (RPB1) that causes cell cycle arrest and genome instability. We now characterize a different cell line that has a temperature-sensitive defect in cell cycle progression, and find that it also has a mutation in RPB1. The temperature-sensitive mutant, tsAF8, of the Syrian hamster cell line, BHK21, arrests at the non-permissive temperature in the mid-G(1) phase. We show that RPB1 in tsAF8--which is found exclusively in the nucleus at the permissive temperature--is also found in the cytoplasm at the non-permissive temperature. Comparison of the DNA sequences of the RPB1 gene in the wild-type and mutant shows the mutant phenotype results from a (hemizygous) C-to-A variation at nucleotide 944 in one RPB1 allele; this gives rise to an ala-to-asp substitution at residue 315 in the protein. Aligning the amino acid sequences from various species reveals that ala(315) is highly conserved in eukaryotes.

Regulation of the catalase gene promoter by Sp1, CCAAT-recognizing factors, and a WT1/Egr-related factor in hydrogen peroxide-resistant HP100 cells

Reactive oxygen species play a critical role in the onset of apoptosis induced by various extracellular stimuli, including ionizing radiation. Therefore active regulation of reactive oxygen species-metabolizing enzymes may be one response to an apoptotic stimulus. In this regard, HP100 cells, H(2)O(2)-resistant variants derived from human leukemia HL60 cells, display an interesting phenotype in which the activity of catalase is constitutively high, whereas its mRNA is reduced after X-ray irradiation. In the present study, we investigated the molecular mechanisms underlying this phenomenon. By combining analyses from nuclear run-on, reporter gene transient transfection, genomic footprinting, site-directed mutagenesis, electrophoretic mobility shift analysis, and Western blotting experiments, we found that constitutively elevated catalase expression is strongly regulated at the transcriptional level by both Sp1 and CCAAT-recognizing factors and that much higher levels of nuclear Sp1 and NF-Y are present in HP100 nuclei as compared with HL60 nuclei. In addition, we demonstrated an X-ray-inducible association of a WT1/Egr-related factor with an overlapping Sp1/Egr-1 recognition sequence located within the core promoter of the catalase gene. This association may lead to inactivation of the promoter by disturbing or competing with the transactivating ability of Sp1.