Presenilin-1 mutations downregulate the signalling pathway of the unfolded-protein response

Missense mutations in the human presenilin-1 (PS1) gene, which is found on chromosome 14, cause early-onset familial Alzheimer's disease (FAD). FAD-linked PS1 variants alter proteolytic processing of the amyloid precursor protein and cause an increase in vulnerability to apoptosis induced by various cell stresses. However, the mechanisms responsible for these phenomena are not clear. Here we report that mutations in PS1 affect the unfolded-protein response (UPR), which responds to the increased amount of unfolded proteins that accumulate in the endoplasmic reticulum (ER) under conditions that cause ER stress. PS1 mutations also lead to decreased expression of GRP78/Bip, a molecular chaperone, present in the ER, that can enable protein folding. Interestingly, GRP78 levels are reduced in the brains of Alzheimer's disease patients. The downregulation of UPR signalling by PS1 mutations is caused by disturbed function of IRE1, which is the proximal sensor of conditions in the ER lumen. Overexpression of GRP78 in neuroblastoma cells bearing PS1 mutants almost completely restores resistance to ER stress to the level of cells expressing wild-type PS1. These results show that mutations in PS1 may increase vulnerability to ER stress by altering the UPR signalling pathway.

Differential regulation of interleukin 17 and interferon gamma production in inflammatory bowel disease

BACKGROUND AND AIMS

Interleukin 17 (IL17) is now known to be involved in a number of chronic inflammatory disorders. However, the mechanisms regulating its production in inflammatory bowel disease (IBD) are still unclear.

METHODS

Endoscopic biopsies or surgical specimens were taken from inflamed and uninflamed colonic mucosa of 72 patients with IBD (38 with Crohn's disease and 34 with ulcerative colitis), and normal colon of 38 control subjects. IL17 and interferon gamma (IFNgamma) were detected by ELISA in the supernatants of biopsies cultured ex vivo, and anti-CD3/CD28-stimulated lamina propria mononuclear cells (LPMCs) incubated with IL12, IL23, IL1beta plus IL6, transforming growth factor beta1 (TGFbeta1), or anti-IL21 neutralising antibody. Intracellular flow cytometry was performed to analyse mucosal Th17 and Th1/Th17 cells.

RESULTS

IL17 production by organ culture biopsies was higher in IBD inflamed mucosa than IBD uninflamed mucosa and controls, and was equivalent in amount to IFNgamma. Anti-CD3/CD28-stimulated IBD LPMCs produced higher IL17 amounts compared to controls. The percentages of Th17 and Th1/Th17 cells were increased in patients with IBD. IL23 and IL1beta plus IL6 had no effect on IBD LPMC production of IL17; however, IL12 markedly increased IFNgamma production and decreased IL17 production. TGFbeta1 dose-dependently decreased IFNgamma, but had no significant inhibitory effect on IL17 production. Blocking IL21 significantly downregulated IL17 production.

CONCLUSIONS

Our findings support a role for IL12, TGFbeta and IL21 in modulating IL17/IFNgamma production in IBD. The abundant IL17 in inflamed IBD mucosa may help explain the relative lack of efficacy of anti-IFNgamma antibodies in clinical trials of Crohn's disease.

A molecular chaperone inducer protects neurons from ER stress

The endoplasmic reticulum (ER) stress response is a defense system for dealing with the accumulation of unfolded proteins in the ER lumen. Recent reports have shown that ER stress is involved in the pathology of some neurodegenerative diseases and cerebral ischemia. In a screen for compounds that induce the ER-mediated chaperone BiP (immunoglobulin heavy-chain binding protein)/GRP78 (78 kDa glucose-regulated protein), we identified BiP inducer X (BIX). BIX preferentially induced BiP with slight inductions of GRP94 (94 kDa glucose-regulated protein), calreticulin, and C/EBP homologous protein. The induction of BiP mRNA by BIX was mediated by activation of ER stress response elements upstream of the BiP gene, through the ATF6 (activating transcription factor 6) pathway. Pretreatment of neuroblastoma cells with BIX reduced cell death induced by ER stress. Intracerebroventricular pretreatment with BIX reduced the area of infarction due to focal cerebral ischemia in mice. In the penumbra of BIX-treated mice, ER stress-induced apoptosis was suppressed, leading to a reduction in the number of apoptotic cells. Considering these results together, it appears that BIX induces BiP to prevent neuronal death by ER stress, suggesting that it may be a potential therapeutic agent for cerebral diseases caused by ER stress.

Phylogenetic diversity of the intestinal bacterial community in the termite Reticulitermes speratus

The phylogenetic diversity of the intestinal microflora of a lower termite, Reticulitermes speratus, was examined by a strategy which does not rely on cultivation of the resident microorganisms. Small-subunit rRNA genes (16S rDNAs) were directly amplified from the mixed-population DNA of the termite gut by the PCR and were clonally isolated. Analysis of partial 16S rDNA sequences showed the existence of well-characterized genera as well as the presence of bacterial species for which no 16S rDNA sequence data are available. Of 55 clones sequenced, 45 were phylogenetically affiliated with four of the major groups of the domain Bacteria: the Proteobacteria, the spirochete group, the Bacteroides group, and the low-G+C-content gram-positive bacteria. Within the Proteobacteria, the 16S rDNA clones showed a close relationship to those of cultivated species of enteric bacteria and sulfate-reducing bacteria, while the 16S rDNA clones in the remaining three groups showed only distant relationships to those of known organisms in these groups. Of the remaining 10 clones, among which 8 clones formed a cluster, there was only very low sequence similarity to known 16S rRNA sequences. None of these clones were affiliated with any of the major groups within the domain Bacteria. The 16S rDNA gene sequence data show that the majority of the intestinal microflora of R. speratus consists of new, uncultured species previously unknown to microbiologists.

Inhibition of aldosterone production in the adrenal glomerulosa by atrial natriuretic factor

Several forms of the polypeptide atrial natriuretic factor (ANF) have been isolated recently from rat and human atria and identified; they are probably associated with the secretory granules of atrial tissue. The potent ability of ANFs to increase urine sodium content is mediated by their direct action on the kidney. We report here the high intrinsic activity of a synthetic replicate of one form of this molecule, ANF(8-33)(ref. 7), to inhibit directly basal aldosterone secretion and its ability to antagonize the stimulatory effects of adrenocorticotropin (ACTH) and angiotensin II (AN-II) on the secretion of aldosterone by rat adrenoglomerulosa cells in vitro. Our results suggest that ANF is of clinical importance in the management of aldosterone-dependent hypertension by modifying the adrenocortical response to endogenous ACTH and AN-II.

Novel mutations in the connexin 26 gene (GJB2) responsible for childhood deafness in the Japanese population

Mutations in the connexin 26 gene (GJB2), which encodes a gap-junction protein and is expressed in the inner ear, have been shown to be responsible for a major part of nonsyndromic hereditary prelingual (early-childhood) deafness in Caucasians. We have sequenced the GJB2 gene in 39 Japanese patients with prelingual deafness (group 1), 39 Japanese patients with postlingual progressive sensorineural hearing loss (group 2), and 63 Japanese individuals with normal hearing (group 3). Three novel mutations were identified in group 1: a single nucleotide deletion (235delC), a 16-bp deletion (176-191 del (16)), and a nonsense mutation (Y136X) in five unrelated patients. The 235delC mutation was most frequently observed, accounting for seven alleles in 10 mutant alleles. Screening of 203 unrelated normal individuals for the three mutations indicated that the carrier frequency of the 235delC mutation was 2/203 in the Japanese population. No mutation was found in group-2 patients. We also identified two novel polymorphisms (E114G and I203T) as well as two previously reported polymorphisms (V27I andV37I). Genotyping with these four polymorphisms allowed normal Japanese alleles to be classified into seven haplotypes. All 235delC mutant alleles identified in four patients resided only on haplotype type 1. These findings indicate that GJB2 mutations are also responsible for prelingual deafness in Japan.

Disturbed activation of endoplasmic reticulum stress transducers by familial Alzheimer's disease-linked presenilin-1 mutations

Recent studies have shown independently that presenilin-1 (PS1) null mutants and familial Alzheimer's disease (FAD)-linked mutants should both down-regulate signaling of the unfolded protein response (UPR). However, it is difficult to accept that both mutants possess the same effects on the UPR. Furthermore, contrary to these observations, neither loss of PS1 and PS2 function nor expression of FAD-linked PS1 mutants were reported to have a discernable impact on the UPR. Therefore, re-examination and detailed analyses are needed to clarify the relationship between PS1 function and UPR signaling. Here, we report that PS1/PS2 null and dominant negative PS1 mutants, which are mutated at aspartate residue 257 or 385, did not affect signaling of the UPR. In contrast, FAD-linked PS1 mutants were confirmed to disturb UPR signaling by inhibiting activation of both Ire1alpha and ATF6, both of which are endoplasmic reticulum (ER) stress transducers in the UPR. Furthermore, PS1 mutants also disturbed activation of PERK (PKR-like ER kinase), which plays a crucial role in inhibiting translation during ER stress. Taken together, these observations suggested that PS1 mutations could affect signaling pathways controlled by each of the respective ER-stress transducers, possibly through a gain-of-function.

Screening the p53 status of human cell lines using a yeast functional assay

We have screened the p53 status of 156 human cell lines, including 142 tumor cell lines from 27 different tumor types and 14 cell lines from normal tissues by using functional analysis of separated alleles in yeast. This assay enables us to score wild-type p53 expression on the basis of the ability of expressed p53 to transactivate the reporter gene HIS3 via the p53-responsive GAL1 promotor in Saccharomyces cerevisiae. Of 142 tumor cell lines, at least 104 lines (73.2%) were found to express the mutated p53 gene: 94 lines (66.2%) were mutated in both alleles, three lines (2.1%) were heterozygous, and no p53 cDNA was amplified from seven lines (4.9%). Of the 14 cell lines originating from normal tissues, all the transformed or immortalized cell lines expressed mutant p53 only. Yeast cells expressing mutant p53 derived from 94 cell lines were analyzed for temperature-sensitive growth. p53 cDNA from eight cell lines showed p53-dependent temperature-sensitive growth, growing at 30 degrees C but not at 37 degrees C. Four temperature-sensitive p53 mutations were isolated: CAT-->CGT at codon 214 (H214R), TAC-->TGC at codon 234 (Y234C), GTG-->ATG at codon 272 (V272M), and GAG-->AAG (E285K). Functionally wild-type p53 was detected in 38 tumor cell lines (26.8%) and all of the diploid fibroblasts at early and late population doubling levels. These results strongly support the previous findings that p53 inactivation is one of the most frequent genetic events that occurs during carcinogenesis and immortalization.

Characterization of a gene responsible for the Na+/H+ antiporter system of alkalophilic Bacillus species strain C-125

An alkali-sensitive mutant, 38154, of the alkalophilic Bacillus sp. strain C-125 could not grow at an alkaline pH. The nucleotide sequence of a 3.7 kb parental DNA fragment that recovers the growth of 38154 at alkaline pH has four open reading frames (ORF1-4). By subcloning the fragment, we demonstrated that a 0.25 kb DNA region is responsible for the recovery. Direct sequencing of the mutant's corresponding region revealed a G to A substitution. The mutation resulted in an amino acid substitution from Gly-393 to Arg of the putative ORF1 product, which was deduced to be an 804-amino-acid polypeptide with a molecular weight of 89,070. The N-terminal part of the putative ORF1 product showed amino acid similarity to those of the chain-5 products of eukaryotic NADH quinone oxidoreductases. Membrane vesicles prepared from 38154 did not show membrane potential (delta psi)-driven Na+/H+ antiporter activity. Antiporter activity was resumed by introducing a parental DNA fragment which recovered the mutant's alkalophily. These results indicate that the mutation in 38154 affects, either directly or indirectly, the electrogenic Na+/H+ antiporter activity. This is the first report which shows that a gene responsible for the Na+/H+ antiporter system is important in the alkalophily of alkalophilic microorganisms.

Vascular endothelial growth factor-C expression and its relationship to pelvic lymph node status in invasive cervical cancer

Vascular endothelial growth factor-C (VEGF-C) has been implicated in lymphangiogenesis, the process of new lymphatics formation. The present study investigated VEGF-C mRNA expression in invasive cervical cancer tissue. Additionally, the association of VEGF-C mRNA with clinicopathological features was examined. VEGF-C mRNA expression was assessed by reverse transcription-polymerase chain reaction using beta-action as an internal control. 75 patients presenting with invasive cervical cancer were included in the trial. VEGF-C mRNA expression was markedly higher in tumours in which pelvic lymph node metastasis was diagnosed by magnetic resonance (MR) imaging (P = 0.002). 53 patients displaying stage Ib-IIb cervical cancer underwent radical hysterectomy and pelvic lymphadenectomy. VEGF-C expression was significantly higher in tumours exhibiting deep stromal invasion, pelvic lymph node metastasis and lymph-vascular space involvement (P = 0.016, P = 0.006 and P = 0.036, respectively). Multivariate analysis revealed VEGF-C mRNA expression to be the sole independent factor influencing pelvic lymph node metastasis. Subjects demonstrating VEGF-C mRNA expression displayed significantly poorer prognoses than those lacking VEGF-C mRNA expression (P = 0.049). These findings provide evidence supporting the involvement of VEGF-C expression in the promotion of lymph node metastasis in cervical cancer. Furthermore, examination of VEGF-C expression in biopsy specimens may be beneficial in the prediction of pelvic lymph node metastasis.

Purification and Properties of Extracellular Amylase from the Hyperthermophilic Archaeon Thermococcus profundus DT5432

A hyperthermophilic archaeon, Thermococcus profundus DT5432, produced extracellular thermostable amylases. One of the amylases (amylase S) was purified to homogeneity by ammonium sulfate precipitation, DEAE-Toyopearl chromatography, and gel filtration on Superdex 200HR. The molecular weight of the enzyme was estimated to be 42,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amylase exhibited maximal activity at pH 5.5 to 6.0 and was stable in the range of pH 5.9 to 9.8. The optimum temperature for the activity was 80(deg)C. Half-life of the enzyme was 3 h at 80(deg)C and 15 min at 90(deg)C. Thermostability of the enzyme was enhanced in the presence of 5 mM Ca(sup2+) or 0.5% soluble starch at temperatures above 80(deg)C. The enzyme activity was inhibited in the presence of 5 mM iodoacetic acid or 1 mM N-bromosuccinimide, suggesting that cysteine and tryptophan residues play an important role in the catalytic action. The amylase hydrolyzed soluble starch, amylose, amylopectin, and glycogen to produce maltose and maltotriose of (alpha)-configuration as the main products. Smaller amounts of larger maltooligosaccharides were also produced with a trace amount of glucose. Pullulan; (alpha)-, (beta)-, and (gamma)-cyclodextrins; maltose; and maltotriose were not hydrolyzed.

The unfolded protein response and Alzheimer's disease

Disruption of calcium homeostasis, inhibition of protein glycosylation, and reduction of disulfide bonds provoke accumulation of unfolded protein in the endoplasmic reticulum (ER), and are therefore a type of 'ER stress'. Normal cells respond to ER stress by increasing transcription of genes encoding ER-resident chaperones such as GRP78/BiP, GRP94 and protein disulfide isomerase to facilitate protein folding. This induction system is termed the unfolded protein response. Familial Alzheimer's disease-linked presenilin-1 (PS1) mutation downregulates the unfolded protein response and leads to vulnerability to ER stress. The mechanisms by which mutant PS1 affects the ER stress response are attributed to the inhibited activation of ER stress transducers such as IRE1, PERK and ATF6.

Cloning, expression, and characterization of a novel UDP-galactose:beta-N-acetylglucosamine beta1,3-galactosyltransferase (beta3Gal-T5) responsible for synthesis of type 1 chain in colorectal and pancreatic epithelia and tumor cells derived therefrom

The sialyl Lewis a antigen is a well known tumor marker, CA19-9, which is frequently elevated in the serum in gastrointestinal and pancreatic cancers. UDP-galactose:N-acetylglucosamine beta1, 3-galactosyltransferase(s) (beta3Gal-Ts) are required for the synthesis of the sialyl Lewis a epitope. In the present study, a novel beta3Gal-T, named beta3Gal-T5, was isolated from a Colo205 cDNA library using a degenerate primer strategy based on the amino acid sequences of the four human beta3Gal-T genes cloned to date. Transfection experiments demonstrated that HCT-15 cells transfected with the beta3Gal-T5 gene expressed all the type 1 Lewis antigens. In gastrointestinal and pancreatic cancer cell lines, the amounts of beta3Gal-T5 transcripts were quite well correlated with the amounts of the sialyl Lewis a antigens. The beta1,3Gal-T activity toward agalacto-lacto-N-neotetraose was also well correlated with the amounts of beta3Gal-T5 transcripts in a series of cultured cancer cells, and in Namalwa and HCT-15 cells transfected with the beta3Gal-T5 gene. Thus, the beta3Gal-T5 gene is the most probable candidate responsible for the synthesis of the type 1 Lewis antigens in gastrointestinal and pancreatic epithelia and tumor cells derived therefrom. In addition, beta3Gal-T5 is a key enzyme that determines the amounts of the type 1 Lewis antigens including the sialyl Lewis a antigen.

Cloning and expression of a human gene encoding an N-acetylgalactosamine-alpha2,6-sialyltransferase (ST6GalNAc I): a candidate for synthesis of cancer-associated sialyl-Tn antigens

The sialyl-Tn (sTn) antigen is a well known cancer-associated antigen, the expression of which is related to the prognosis of cancer patients. We aimed to isolate a human gene encoding an N -acetylgalactosamine alpha2,6-sialyltransferase which synthesizes sTn antigen, and to characterize the enzyme. Degenerate primers encoding sialyl motifs were used for the polymerase chain reaction to amplify complementary DNAs prepared from RNAs of human pyloric mucosae with intestinal metaplasia, which abundantly expressed sTn antigen, followed by screening of full-length cDNAs using the amplified DNA fragment as a probe. We isolated two human cDNA clones, long-form (2.46 kb) and short-form (2.23 kb) cDNAs. The former encodes an active enzyme with a predicted 600 amino acid sequence. The latter, a splice-variant of the long-form, encodes an inactive enzyme. HCT15 human colorectal cancer cells stably expressing the long-form cDNA expressed sTn epitopes on O -glycans. The long form cDNA was considered to encode a human homologue of chick ST6GalNAc I for the following reasons: (1) the putative amino acid sequence showed greater homology to that of chick ST6GalNAc I (55%) compared to other sialyltransferases, (2) it encodes the extraordinarily long stem region that is a typical feature of chick ST6GalNAc I, and (3) the substrate specificity was very similar to that of chick ST6GalNAc I. In situ hybridization demonstrated that the localization of transcripts correlated well with that of sTn antigen in gastric cancer cells and Goblet cells in intestinal metaplastic glands. Thus, we determined that the long-form cDNA of the human ST6GalNAc I gene encodes the probable candidate for the human sTn synthase(s).

Microbispora corallina sp. nov., a new species of the genus Microbispora isolated from Thai soil

Two actinomycete strains, DF-28 and DF-32T, were isolated from soil samples collected in a deciduous dipterocarp forest in Thailand. They produced longitudinally paired spores on the tips of short sporophores alternately branched from aerial hyphae, and the chemotaxonomic properties of the isolates were the same as those of members of the family Streptosporangiaceae. These phenotypic properties, together with the results of a phylogenetic analysis based on 16S rRNA gene sequences, indicated that these isolates should be assigned to the genus Microbispora. The two isolates showed more than 93% DNA relatedness to each other, but their relatedness to any previously described species of the genus Microbispora was only 45% or less. They were distinguishable from previously described Microbispora spp. by a combination of physiological and biochemical properties. Therefore, a new species is proposed for these strains, under the name Microbispora corallina sp. nov. The type strain is strain DF-32T (= JCM 10267T).

Establishment of a new extrahepatic bile duct carcinoma cell line, TFK-1

A new human extrahepatic bile duct carcinoma cell line (TFK-1) was established from a surgically resected tumor specimen, which was histologically diagnosed as partly papillary adenocarcinoma and partly differentiated tubular adenocarcinoma. The tumor cells cultured in RPMI-1640 medium supplemented with 10% FBS grew as monolayers showing epithelial-like morphology with a population doubling time of 37 hr during exponential growth at passage 40. Chromosome number was distributed in the range of 72 to 76, with a modal number of 73. Tumor markers (CEA, CA19-9, ST-439, DUPAN-2) were negative in culture supernatant and plasma of SCID mice grafted with TFK-1 cells. Though no point mutation at 12 codon of K-ras was detected, expression of c-erb B-2 product and MUC1 antigen was positive. TFK-1 is the third cell line established from extrahepatic bile duct carcinomas in the world literature, and should provide useful information on various aspects of this type of neoplasm.

Alpha1,3-fucosyltransferase IX (Fuc-TIX) is very highly conserved between human and mouse; molecular cloning, characterization and tissue distribution of human Fuc-TIX

The amino acid sequence of Fuc-TIX is very highly conserved between mouse and human. The number of non-synonymous nucleotide substitutions of the Fuc-TIX gene between human and mouse was strikingly low, and almost equivalent to that of the alpha-actin gene. This indicates that Fuc-TIX is under a strong selective pressure of preservation during evolution. The human Fuc-TIX (hFuc-TIX) showed a unique characteristics, i.e. hFuc-TIX was not activated by Mn2+ and Co2+, whereas hFuc-TIV and hFuc-TVI were activated by the cations. The hFuc-TIX transcripts were abundantly expressed in brain and stomach, and interestingly were detected in spleen and peripheral blood leukocytes.

Endocrine disrupting chemicals, phthalic acid and nonylphenol, activate Pregnane X receptor-mediated transcription

Recently, Pregnane X receptor (PXR), a new member of the nuclear receptor superfamily, was shown to mediate the effects of several steroid hormones, such as progesterone, glucocorticoid, pregnenolone, and xenobiotics on cytochrome P450 3A genes (CYP3A) through the specific DNA sequence for CYP3A, suggesting that PXR may play a role in steroid hormone metabolism. In this paper, we demonstrated that phthalic acid and nonylphenol, endocrine-disrupting chemicals (EDCs), stimulated PXR-mediated transcription at concentrations comparable to those at which they activate estrogen receptor-mediated transcription using a transient reporter gene expression assay in COS-7 cells. However, bisphenol A, another EDC, had no effect on PXR-mediated transcription, although this chemical significantly enhanced ER-mediated transcription. In the yeast two-hybrid protein interaction assay, PXR interacted with two nuclear receptor coactivator proteins, steroid hormone receptor coactivator-1 and receptor interacting protein 140, in the presence of phthalic acid or nonylphenol. Thus, EDC-occupied PXR may regulate its specific gene expression through the receptor-coactivator interaction. In contrast, these EDCs had no effect on the interaction between PXR and suppressor for gal 1, a component of proteasome. Finally, the expression of CYP3A1 mRNA in the liver of rats exposed to phthalic acid or nonylphenol markedly increased compared with that in rats treated with estradiol, bisphenol A, or ethanol as assessed by competitive RT-PCR. These data suggest that EDCs may affect endocrine functions by altering steroid hormone metabolism through PXR.

Cospeciation in the triplex symbiosis of termite gut protists (Pseudotrichonympha spp.), their hosts, and their bacterial endosymbionts

A number of cophylogenetic relationships between two organisms namely a host and a symbiont or parasite have been studied to date; however, organismal interactions in nature usually involve multiple members. Here, we investigated the cospeciation of a triplex symbiotic system comprising a hierarchy of three organisms -- termites of the family Rhinotermitidae, cellulolytic protists of the genus Pseudotrichonympha in the guts of these termites, and intracellular bacterial symbionts of the protists. The molecular phylogeny was inferred based on two mitochondrial genes for the termites and nuclear small-subunit rRNA genes for the protists and their endosymbionts, and these were compared. Although intestinal microorganisms are generally considered to have looser associations with the host than intracellular symbionts, the Pseudotrichonympha protists showed almost complete codivergence with the host termites, probably due to strict transmissions by proctodeal trophallaxis or coprophagy based on the social behaviour of the termites. Except for one case, the endosymbiotic bacteria of the protists formed a monophyletic lineage in the order Bacteroidales, and the branching pattern was almost identical to those of the protists and the termites. However, some non-codivergent evolutionary events were evident. The members of this triplex symbiotic system appear to have cospeciated during their evolution with minor exceptions; the evolutionary relationships were probably established by termite sociality and the complex microbial community in the gut.

Clarification of the relationship between the members of the family Thermomonosporaceae on the basis of 16S rDNA, 16S-23S rRNA internal transcribed spacer and 23S rDNA sequences and chemotaxonomic analyses

To resolve relationships between members of the family Thermomonosporaceae, phylogenetic analyses using three sets of nucleotide sequences from 16S rDNA, 23S rDNA and the 16S-23S internal transcribed spacer (ITS) were carried out. Nearly all species of the family were included in this study. On the basis of congruous phylogenetic results and chemotaxonomic data, the following proposals are made. First, Actinomadura libanotica, Actinomadura aurantiaca, Actinomadura glomerata and Actinomadura longicatena are transferred to the genus Actinocorallia as Actinocorallia libanotica comb. nov., Actinocorallia aurantiaca comb. nov., Actinocorallia glomerata comb. nov. and Actinocorallia longicatena comb. nov., respectively. All the species of this genus are phylogenetically coherent and of phospholipid type PII (presence of phosphatidylethanolamine), distinguishing them from other Actinomadura species that are of phospholipid type PI (absence of diagnostic phospholipids). Second, Excellospora viridilutea is transferred to the genus Actinomadura as Actinomadura viridilutea comb. nov. As a result of the proposed transfers, the family Thermomonosporaceae now contains four genera Thermomonospora, Actinomadura, Actinocorallia and Spirillospora. The genus Actinocorallia and family Thermomonosporaceae are redescribed.

Two distinct mechanisms cause heterogeneity of 16S rRNA

To investigate the frequency of heterogeneity among the multiple 16S rRNA genes within a single microorganism, we determined directly the 120-bp nucleotide sequences containing the hypervariable alpha region of the 16S rRNA gene from 475 Streptomyces strains. Display of the direct sequencing patterns revealed the existence of 136 heterogeneous loci among a total of 33 strains. The heterogeneous loci were detected only in the stem region designated helix 10. All of the substitutions conserved the relevant secondary structure. The 33 strains were divided into two groups: one group, including 22 strains, had less than two heterogeneous bases; the other group, including 11 strains, had five or more heterogeneous bases. The two groups were different in their combinations of heterogeneous bases. The former mainly contained transitional substitutions, and the latter was mainly composed of transversional substitutions, suggesting that at least two mechanisms, possibly misincorporation during DNA replication and horizontal gene transfer, cause rRNA heterogeneity.

Increased production of beta-amyloid and vulnerability to endoplasmic reticulum stress by an aberrant spliced form of presenilin 2

An alternative spliced form of the presinilin 2 (PS2) gene (PS2V) lacking exon 5 has previously been reported to be expressed in human brains in sporadic Alzheimer's disease (AD). PS2V encodes the amino-terminal portion of PS2, which contains residues Met1-Leu119 and 5 additional amino acid residues (SSMAG) at its carboxyl terminus. Here we report that PS2V protein impaired the signaling pathway of the unfolded protein response, similarly to familial AD-linked PS1 mutants and caused significant increases in the production of both amyloid beta40 and beta42. Interestingly, PS2V-encoding protein was expressed in neuropathologically affected neurons of the hippocampal CA1 region and temporal cortex in AD patients. These findings suggest that the aberrant splicing of the PS2 gene may be implicated in the neuropathology of sporadic AD.

Melanin production in cultured albino melanocytes transfected with mouse tyrosinase cDNA

An attempt was made in the present study to express mouse tyrosinase cDNAs fused with the authentic genomic 5' non-coding flanking sequence in cultured albino melanocytes. One of the cDNA sequences, which expressed successfully and produced melanin pigments, was analyzed with respect to deduced amino acid sequence. Sequencing of the tyrosinase genomic gene revealed the existence of several sets of a characteristic structure which consists of a chain of two successive stem structures, CCAAT-homology and TATA box at its 5' non-coding region. It seems possible that this region represents the regulatory element of the tyrosinase gene. Unusually long GA cluster at 5' upstream region was also found.