The sequence of the human genome

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.

A Toll-like receptor recognizes bacterial DNA

DNA from bacteria has stimulatory effects on mammalian immune cells, which depend on the presence of unmethylated CpG dinucleotides in the bacterial DNA. In contrast, mammalian DNA has a low frequency of CpG dinucleotides, and these are mostly methylated; therefore, mammalian DNA does not have immuno-stimulatory activity. CpG DNA induces a strong T-helper-1-like inflammatory response. Accumulating evidence has revealed the therapeutic potential of CpG DNA as adjuvants for vaccination strategies for cancer, allergy and infectious diseases. Despite its promising clinical use, the molecular mechanism by which CpG DNA activates immune cells remains unclear. Here we show that cellular response to CpG DNA is mediated by a Toll-like receptor, TLR9. TLR9-deficient (TLR9-/-) mice did not show any response to CpG DNA, including proliferation of splenocytes, inflammatory cytokine production from macrophages and maturation of dendritic cells. TLR9-/- mice showed resistance to the lethal effect of CpG DNA without any elevation of serum pro-inflammatory cytokine levels. The in vivo CpG-DNA-mediated T-helper type-1 response was also abolished in TLR9-/- mice. Thus, vertebrate immune systems appear to have evolved a specific Toll-like receptor that distinguishes bacterial DNA from self-DNA.

Sequence analysis of the genome of the unicellular cyanobacterium Synechocystis sp. strain PCC6803. II. Sequence determination of the entire genome and assignment of potential protein-coding regions

The sequence determination of the entire genome of the Synechocystis sp. strain PCC6803 was completed. The total length of the genome finally confirmed was 3,573,470 bp, including the previously reported sequence of 1,003,450 bp from map position 64% to 92% of the genome. The entire sequence was assembled from the sequences of the physical map-based contigs of cosmid clones and of lambda clones and long PCR products which were used for gap-filling. The accuracy of the sequence was guaranteed by analysis of both strands of DNA through the entire genome. The authenticity of the assembled sequence was supported by restriction analysis of long PCR products, which were directly amplified from the genomic DNA using the assembled sequence data. To predict the potential protein-coding regions, analysis of open reading frames (ORFs), analysis by the GeneMark program and similarity search to databases were performed. As a result, a total of 3,168 potential protein genes were assigned on the genome, in which 145 (4.6%) were identical to reported genes and 1,257 (39.6%) and 340 (10.8%) showed similarity to reported and hypothetical genes, respectively. The remaining 1,426 (45.0%) had no apparent similarity to any genes in databases. Among the potential protein genes assigned, 128 were related to the genes participating in photosynthetic reactions. The sum of the sequences coding for potential protein genes occupies 87% of the genome length. By adding rRNA and tRNA genes, therefore, the genome has a very compact arrangement of protein- and RNA-coding regions. A notable feature on the gene organization of the genome was that 99 ORFs, which showed similarity to transposase genes and could be classified into 6 groups, were found spread all over the genome, and at least 26 of them appeared to remain intact. The result implies that rearrangement of the genome occurred frequently during and after establishment of this species.

Lipopolysaccharide stimulates the MyD88-independent pathway and results in activation of IFN-regulatory factor 3 and the expression of a subset of lipopolysaccharide-inducible genes

Bacterial lipopolysaccharide (LPS) triggers innate immune responses through Toll-like receptor (TLR) 4, a member of the TLR family that participates in pathogen recognition. TLRs recruit a cytoplasmic protein, MyD88, upon pathogen recognition, mediating its function for immune responses. Two major pathways for LPS have been suggested in recent studies, which are referred to as MyD88-dependent and -independent pathways. We report in this study the characterization of the MyD88-independent pathway via TLR4. MyD88-deficient cells failed to produce inflammatory cytokines in response to LPS, whereas they responded to LPS by activating IFN-regulatory factor 3 as well as inducing the genes containing IFN-stimulated regulatory elements such as IP-10. In contrast, a lipopeptide that activates TLR2 had no ability to activate IFN-regulatory factor 3. The MyD88-independent pathway was also activated in cells lacking both MyD88 and TNFR-associated factor 6. Thus, TLR4 signaling is composed of at least two distinct pathways, a MyD88-dependent pathway that is critical to the induction of inflammatory cytokines and a MyD88/TNFR-associated factor 6-independent pathway that regulates induction of IP-10.

Modulation of Akt kinase activity by binding to Hsp90

Serine/threonine kinase Akt/PKB is a downstream effector molecule of phosphoinositide 3-kinase and is thought to mediate many biological actions toward anti-apoptotic responses. We found that Akt formed a complex with a 90-kDa heat-shock protein (Hsp90) in vivo. By constructing deletion mutants, we identified that amino acid residues 229-309 of Akt were involved in the binding to Hsp90 and amino acid residues 327-340 of Hsp90beta were involved in the binding to Akt. Inhibition of Akt-Hsp90 binding led to the dephosphorylation and inactivation of Akt, which increased sensitivity of the cells to apoptosis-inducing stimulus. The dephosphorylation of Akt was caused by an increase in protein phosphatase 2A (PP2A)-mediated dephosphorylation and not by a decrease in 3-phosphoinositide-dependent protein kinase-1-mediated phosphorylation. These results indicate that Hsp90 plays an important role in maintaining Akt kinase activity by preventing PP2A-mediated dephosphorylation.

Activation tagging in Arabidopsis

Activation tagging using T-DNA vectors that contain multimerized transcriptional enhancers from the cauliflower mosaic virus (CaMV) 35S gene has been applied to Arabidopsis plants. New activation-tagging vectors that confer resistance to the antibiotic kanamycin or the herbicide glufosinate have been used to generate several tens of thousands of transformed plants. From these, over 30 dominant mutants with various phenotypes have been isolated. Analysis of a subset of mutants has shown that overexpressed genes are almost always found immediately adjacent to the inserted CaMV 35S enhancers, at distances ranging from 380 bp to 3.6 kb. In at least one case, the CaMV 35S enhancers led primarily to an enhancement of the endogenous expression pattern rather than to constitutive ectopic expression, suggesting that the CaMV 35S enhancers used here act differently than the complete CaMV 35S promoter. This has important implications for the spectrum of genes that will be discovered by this method.

Cutting edge: endotoxin tolerance in mouse peritoneal macrophages correlates with down-regulation of surface toll-like receptor 4 expression

Monocytes/macrophages exposed to LPS show reduced responses to second stimulation with LPS, which is termed LPS tolerance. In this study, we investigated molecular mechanism of LPS tolerance in macrophages. Mouse peritoneal macrophages pre-exposed to LPS exhibited reduced production of inflammatory cytokines in a time- and dose-dependent manner. Activation of neither IL-1 receptor-associated kinase nor NF-kappaB was observed in macrophages that became tolerant by LPS pretreatment, indicating that the proximal event in Toll-like receptor 4 (TLR4)-MyD88-dependent signaling is affected in tolerant macrophages. Although TLR4 mRNA expression significantly decreased within a few hours of LPS pretreatment and returned to the original level at 24 h, the surface TLR4 expression began to decrease within 1 h, with a gradual decrease after that, and remained suppressed over 24 h. A decrease in inflammatory cytokine production in tolerant macrophages well correlates with down-regulation of the surface TLR4 expression, which may explain one of the mechanisms for LPS tolerance.

Complete genome structure of the nitrogen-fixing symbiotic bacterium Mesorhizobium loti

The complete nucleotide sequence of the genome of a symbiotic bacterium Mesorhizobium loti strain MAFF303099 was determined. The genome of M. loti consisted of a single chromosome (7,036,071 bp) and two plasmids, designated as pMLa (351,911 bp) and pMLb (208, 315 bp). The chromosome comprises 6752 potential protein-coding genes, two sets of rRNA genes and 50 tRNA genes representing 47 tRNA species. Fifty-four percent of the potential protein genes showed sequence similarity to genes of known function, 21% to hypothetical genes, and the remaining 25% had no apparent similarity to reported genes. A 611-kb DNA segment, a highly probable candidate of a symbiotic island, was identified, and 30 genes for nitrogen fixation and 24 genes for nodulation were assigned in this region. Codon usage analysis suggested that the symbiotic island as well as the plasmids originated and were transmitted from other genetic systems. The genomes of two plasmids, pMLa and pMLb, contained 320 and 209 potential protein-coding genes, respectively, for a variety of biological functions. These include genes for the ABC-transporter system, phosphate assimilation, two-component system, DNA replication and conjugation, but only one gene for nodulation was identified.

Safety and cognitive effect of frontal DC brain polarization in healthy individuals

BACKGROUND

Data from the human motor cortex suggest that, depending on polarity, direct current (DC) brain polarization can depress or activate cortical neurons. Activating effects on the frontal lobe might be beneficial for patients with frontal lobe disorders. This phase 1 study tested the safety of frontal DC, including its effects on frontal and other brain functions.

METHODS

The authors applied 20 minutes of anodal, cathodal, or sham DC to the left prefrontal cortex in three groups of right-handed subjects and looked for effects on global measures of processing and psychomotor speed, emotion, and verbal fluency, a measure of local cortical function. In one experiment (n = 30), the authors tested before and after 1 mA DC and monitored EEG in 9 subjects. In two other experiments using 1 mA (n = 43) and 2 mA (n = 30), the authors tested before and then starting 5 minutes after the onset of DC.

RESULTS

All subjects tolerated DC well. There were no significant effects on performance with 1 mA DC. At 2 mA, verbal fluency improved significantly with anodal and decreased mildly with cathodal DC. There were no clinically significant effects on the other measures.

CONCLUSIONS

Limited exposure to direct current polarization of the prefrontal cortex is safe and can enhance verbal fluency selectively in healthy subjects. As such, it deserves consideration as a procedure to improve frontal lobe function in patients.

Activation of HIF1alpha ubiquitination by a reconstituted von Hippel-Lindau (VHL) tumor suppressor complex

Mutations in the VHL tumor suppressor gene result in constitutive expression of many hypoxia-inducible genes, at least in part because of increases in the cellular level of hypoxia-inducible transcription factor HIF1alpha, which in normal cells is rapidly ubiquitinated and degraded by the proteasome under normoxic conditions. The recent observation that the VHL protein is a subunit of an Skp1-Cul1/Cdc53-F-box (SCF)-like E3 ubiquitin ligase raised the possibility that VHL may be directly responsible for regulating cellular levels of HIF1alpha by targeting it for ubiquitination and proteolysis. In this report, we test this hypothesis directly. We report development of methods for production of the purified recombinant VHL complex and present direct biochemical evidence that it can function with an E1 ubiquitin-activating enzyme and E2 ubiquitin-conjugating enzyme to activate HIF1alpha ubiquitination in vitro. Our findings provide new insight into the function of the VHL tumor suppressor protein, and they provide a foundation for future investigations of the mechanisms underlying VHL regulation of oxygen-dependent gene expression.

Plasma fibrinogen level and the risk of major cardiovascular diseases and nonvascular mortality: an individual participant meta-analysis

CONTEXT

Plasma fibrinogen levels may be associated with the risk of coronary heart disease (CHD) and stroke.

OBJECTIVE

To assess the relationships of fibrinogen levels with risk of major vascular and with risk of nonvascular outcomes based on individual participant data.

DATA SOURCES

Relevant studies were identified by computer-assisted searches, hand searches of reference lists, and personal communication with relevant investigators.

STUDY SELECTION

All identified prospective studies were included with information available on baseline fibrinogen levels and details of subsequent major vascular morbidity and/or cause-specific mortality during at least 1 year of follow-up. Studies were excluded if they recruited participants on the basis of having had a previous history of cardiovascular disease; participants with known preexisting CHD or stroke were excluded.

DATA EXTRACTION

Individual records were provided on each of 154,211 participants in 31 prospective studies. During 1.38 million person-years of follow-up, there were 6944 first nonfatal myocardial infarctions or stroke events and 13,210 deaths. Cause-specific mortality was generally available. Analyses involved proportional hazards modeling with adjustment for confounding by known cardiovascular risk factors and for regression dilution bias.

DATA SYNTHESIS

Within each age group considered (40-59, 60-69, and > or =70 years), there was an approximately log-linear association with usual fibrinogen level for the risk of any CHD, any stroke, other vascular (eg, non-CHD, nonstroke) mortality, and nonvascular mortality. There was no evidence of a threshold within the range of usual fibrinogen level studied at any age. The age- and sex- adjusted hazard ratio per 1-g/L increase in usual fibrinogen level for CHD was 2.42 (95% confidence interval [CI], 2.24-2.60); stroke, 2.06 (95% CI, 1.83-2.33); other vascular mortality, 2.76 (95% CI, 2.28-3.35); and nonvascular mortality, 2.03 (95% CI, 1.90-2.18). The hazard ratios for CHD and stroke were reduced to about 1.8 after further adjustment for measured values of several established vascular risk factors. In a subset of 7011 participants with available C-reactive protein values, the findings for CHD were essentially unchanged following additional adjustment for C-reactive protein. The associations of fibrinogen level with CHD or stroke did not differ substantially according to sex, smoking, blood pressure, blood lipid levels, or several features of study design.

CONCLUSIONS

In this large individual participant meta-analysis, moderately strong associations were found between usual plasma fibrinogen level and the risks of CHD, stroke, other vascular mortality, and nonvascular mortality in a wide range of circumstances in healthy middle-aged adults. Assessment of any causal relevance of elevated fibrinogen levels to disease requires additional research.

Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing

In the favoured core-accretion model of formation of planetary systems, solid planetesimals accumulate to build up planetary cores, which then accrete nebular gas if they are sufficiently massive. Around M-dwarf stars (the most common stars in our Galaxy), this model favours the formation of Earth-mass (M(o)) to Neptune-mass planets with orbital radii of 1 to 10 astronomical units (au), which is consistent with the small number of gas giant planets known to orbit M-dwarf host stars. More than 170 extrasolar planets have been discovered with a wide range of masses and orbital periods, but planets of Neptune's mass or less have not hitherto been detected at separations of more than 0.15 au from normal stars. Here we report the discovery of a 5.5(+5.5)(-2.7) M(o) planetary companion at a separation of 2.6+1.5-0.6 au from a 0.22+0.21-0.11 M(o) M-dwarf star, where M(o) refers to a solar mass. (We propose to name it OGLE-2005-BLG-390Lb, indicating a planetary mass companion to the lens star of the microlensing event.) The mass is lower than that of GJ876d (ref. 5), although the error bars overlap. Our detection suggests that such cool, sub-Neptune-mass planets may be more common than gas giant planets, as predicted by the core accretion theory.

The Elongin BC complex interacts with the conserved SOCS-box motif present in members of the SOCS, ras, WD-40 repeat, and ankyrin repeat families

The Elongin BC complex was identified initially as a positive regulator of RNA polymerase II (Pol II) elongation factor Elongin A and subsequently as a component of the multiprotein von Hippel-Lindau (VHL) tumor suppressor complex, in which it participates in both tumor suppression and negative regulation of hypoxia-inducible genes. Elongin B is a ubiquitin-like protein, and Elongin C is a Skp1-like protein that binds to a BC-box motif that is present in both Elongin A and VHL and is distinct from the conserved F-box motif recognized by Skp1. In this report, we demonstrate that the Elongin BC complex also binds to a functional BC box present in the SOCS box, a sequence motif identified recently in the suppressor of cytokine signaling-1 (SOCS-1) protein, as well as in a collection of additional proteins belonging to the SOCS, ras, WD-40 repeat, SPRY domain, and ankyrin repeat families. In addition, we present evidence (1) that the Elongin BC complex is a component of a multiprotein SOCS-1 complex that attenuates Jak/STAT signaling by binding to Jak2 and inhibiting Jak2 kinase, and (2) that by interacting with the SOCS box, the Elongin BC complex can increase expression of the SOCS-1 protein by inhibiting its degradation. These results suggest that Elongin BC is a multifunctional regulatory complex capable of controlling multiple pathways in the cell through interaction with a short degenerate sequence motif found in many different proteins.

Abnormal B lymphocyte development, activation, and differentiation in mice that lack or overexpress the CD19 signal transduction molecule

CD19-deficient mice were generated to examine the role of CD19 in B cell growth regulation in vivo. Deletion of CD19 had no deleterious effects on the generation of B cells in the bone marrow, but there was a significant reduction in the number of B cells in peripheral lymphoid tissues. B cells from CD19-deficient mice exhibited markedly decreased proliferative responses to mitogens, and serum immunoglobulin levels were also significantly decreased. In contrast, mice that overexpressed CD19 had significant defects in early B cell development in the bone marrow, augmented mitogenic responses, and increased serum immunoglobulin levels. These experiments indicate that CD19 functions to define signaling thresholds for cell surface receptors that regulate B lymphocyte selection, activation, and differentiation.

Conjunction search revisited

Search for conjunctions of highly discriminable features can be rapid or even parallel. This article explores three possible accounts based on (a) perceptual segregation, (b) conjunction detectors, and (c) inhibition controlled separately by two or more distractor features. Search rates for conjunctions of color, size, orientation, and direction of motion correlated closely with an independent measure of perceptual segregation. However, they appeared unrelated to the physiology of single-unit responses. Each dimension contributed additively to conjunction search rates, suggesting that each was checked independently of the others. Unknown targets appear to be found only by serial search for each in turn. Searching through 4 sets of distractors was slower than searching through 2. The results suggest a modification of feature integration theory, in which attention is controlled not only by a unitary "window" but also by a form of feature-based inhibition.

Glycerol reverses the misfolding phenotype of the most common cystic fibrosis mutation

The common delta F508 mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) interferes with the biosynthetic folding of nascent CFTR polypeptides, leading to their retention and rapid degradation in an intracellular compartment proximal to the Golgi apparatus. Neither the pathway by which wild-type CFTR folds nor the mechanism by which the Phe508 deletion interferes with this process is well understood. We have investigated the effect of glycerol, a polyhydric alcohol known to stabilize protein conformation, on the folding of CFTR and delta F508 in vivo. Incubation of transient and stable delta F508 transfectants with 10% glycerol induced a significant accumulation of delta F508 protein bearing complex N-linked oligosaccharides, indicative of their transit to a compartment distal to the endoplasmic reticulum (ER). This accumulation was accompanied by an increase in mean whole cell cAMP activated chloride conductance, suggesting that the glycerol-rescued delta F508 polypeptides form functional plasma membrane CFTR channels. These effects were dose- and time-dependent and fully reversible. Glycerol treatment also stabilized immature (core-glycosylated) delta F508 and CFTR molecules that are normally degraded rapidly. These effects of glycerol were not due to a general disruption of ER quality control processes but appeared to correlate with the degree of temperature sensitivity of specific CFTR mutations. These data suggest a model in which glycerol serves to stabilize an otherwise unstable intermediate in CFTR biosynthesis, maintaining it in a conformation that is competent for folding and subsequent release from the ER quality control apparatus.

CD22 is both a positive and negative regulator of B lymphocyte antigen receptor signal transduction: altered signaling in CD22-deficient mice

B cell activation following antigen receptor cross-linking can be augmented in vitro by ligation of cell surface CD22, which associates with the SHP1 protein tyrosine phosphatase. The targeted deletion of CD22 in mice demonstrated that CD22 differentially regulates antigen receptor signaling in resting and antigen-stimulated B lymphocytes. B cells from CD22-deficient mice exhibited the cell surface phenotype and augmented intracellular calcium responses characteristic of chronically stimulated B cells, as occurs in SHP1-defective mice. Thus, CD22 negatively regulates antigen receptor signaling in the absence of antigen. However, activation of CD22-deficient B lymphocytes by prolonged IgM cross-linking resulted in modest B cell proliferation, demonstrating that CD22 positively regulates antigen receptor signaling in the presence of antigen.

Acute axonal polyneuropathy associated with anti-GM1 antibodies following Campylobacter enteritis

We report 2 patients with Guillain-Barré syndrome (GBS) following Campylobacter jejuni enteritis. Electrophysiologic studies indicated that the predominant process was axonal degeneration of motor nerves, and clinical recovery was poor. Serum testing by thin-layer chromatography and enzyme-linked immunosorbent assay revealed that the sera from both patients contained high titers of IgG antibody against GM1 ganglioside. These cases may represent a subgroup of GBS as acute axonal polyneuropathy following C jejuni enteritis associated with anti-GM1 antibodies.

Connective tissue growth factor gene expression in tissue sections from localized scleroderma, keloid, and other fibrotic skin disorders

Connective tissue growth factor (CTGF) is a novel peptide that exhibits platelet-derived growth factor-like activities and is produced by skin fibroblasts after activation with transforming growth factor-beta. Coordinate expression of transforming growth factor-beta followed by CTGF during wound repair suggests a cascade process for control of tissue regeneration. We recently reported a significant correlation between CTGF mRNA expression and histologic sclerosis in systemic sclerosis. To confirm the relation between CTGF and skin fibrosis, we investigated CTGF gene expression in tissue expression in tissue sections from patients with localized scleroderma, keloid, other sclerotic skin disorders using nonradioactive in situ hybridization. In localized scleroderma, the fibroblasts with positive signals for CTGF mRNA were scattered throughout the sclerotic lesions with no preferential distribution around the inflammatory cells or perivascular regions, whereas the adjacent nonaffected dermis was negative for CTGF mRNA. In keloid tissue, the fibroblasts positive for CTGF mRNA were diffusely distributed, especially in the peripheral expanding lesions. In scar tissue, however, the fibroblasts in the fibrotic lesions showed partially positive signals for CTGF mRNA. In eosinophilic fasciitis, nodular fasciitis, and Dupuytren's contracture, CTGF mRNA was also expressed partially in the fibroblasts of the fibrotic lesions. Our findings reinforce a correlation between CTGF gene expression and skin sclerosis and support the hypothesis that transforming growth factor-beta plays an important role in the pathogenesis of fibrosis, as it is the only inducer for CTGF identified to date.

Complete structure of the chloroplast genome of Arabidopsis thaliana

The complete nucleotide sequence of the chloroplast genome of Arabidopsis thaliana has been determined. The genome as a circular DNA composed of 154,478 bp containing a pair of inverted repeats of 26,264 bp, which are separated by small and large single copy regions of 17,780 bp and 84,170 bp, respectively. A total of 87 potential protein-coding genes including 8 genes duplicated in the inverted repeat regions, 4 ribosomal RNA genes and 37 tRNA genes (30 gene species) representing 20 amino acid species were assigned to the genome on the basis of similarity to the chloroplast genes previously reported for other species. The translated amino acid sequences from respective potential protein-coding genes showed 63.9% to 100% sequence similarity to those of the corresponding genes in the chloroplast genome of Nicotiana tabacum, indicating the occurrence of significant diversity in the chloroplast genes between two dicot plants. The sequence data and gene information are available on the World Wide Web database KAOS (Kazusa Arabidopsis data Opening Site) at http://www.kazusa.or.jp/arabi/.

Initial events of myelination involve Fyn tyrosine kinase signalling

Myelin is the lipoprotein multimembrane that functions as an insulator preventing the flow of ion currents across the axonal membrane and facilitating the conduction of nerve impulses. It is synthesized by oligodendrocytes in the central nervous system at about the time of birth in mammals. During the initial stages of myelination, several proteins are phosphorylated on tyrosine. Among these proteins, we identified Fyn tyrosine kinase, one of the non-receptor-type tyrosine kinases of the Src family. Here we report that Fyn tyrosine kinase is activated during the initial stages of myelination and that it is associated with the large myelin-associated glycoprotein (MAG), an adhesion molecule that has been implicated in myelinogenesis. The Fyn-large MAG association requires amino-terminal domains of Fyn that include SH2 and SH3 (Src homology domains 2 and 3). Crosslinking of large MAG with antibody induces a rapid increase in the specific activity of Fyn kinase. These results indicate that Fyn participates in the initial events of myelination as a signalling molecule downstream of large MAG; indeed, we find that fyn-deficient mice exhibit impaired myelination.

ARR1, a transcription factor for genes immediately responsive to cytokinins

Cytokinins are a class of phytohormones involved in various physiological events of plants. The Arabidopsis sensor histidine kinase CRE1 was recently reported to be a cytokinin receptor. We used a steroid-inducible system to show that the transcription factor-type response regulator ARR1 directs transcriptional activation of the ARR6 gene, which responds to cytokinins without de novo protein synthesis. This fact, together with characteristics of ARR1-overexpressing plants and arr1 mutant plants, indicates that the phosphorelay to ARR1, probably from CRE1, constitutes an intracellular signal transduction occurring immediately after cytokinin perception.

Glycogen synthase kinase 3 beta is identical to tau protein kinase I generating several epitopes of paired helical filaments

We previously reported that tau protein kinase I (TPKI) induced normal tau protein into a state of paired helical filaments (PHF); this is further confirmed here by immunoblot analysis using several antibodies. We also present the amino acid sequence of TPKI, which is identical to glycogen synthase kinase 3 beta (GSK3 beta). Moreover, we found that TPKI activity was inseparable from GSK3 activity throughout the purification procedure. These results indicate that TPKI is identical to GSK3 beta.