bcl-x, a bcl-2-related gene that functions as a dominant regulator of apoptotic cell death

We report the isolation of bcl-x, a bcl-2-related gene that can function as a bcl-2-independent regulator of programmed cell death (apoptosis). Alternative splicing results in two distinct bcl-x mRNAs. The protein product of the larger mRNA, bcl-xL, is similar in size and predicted structure to Bcl-2. When stably transfected into an IL-3-dependent cell line, bcl-xL inhibits cell death upon growth factor withdrawal at least as well as bcl-2. Surprisingly, the second mRNA species, bcl-xS, encodes a protein that inhibits the ability of bcl-2 to enhance the survival of growth factor-deprived cells. In vivo, bcl-xS mRNA is expressed at high levels in cells that undergo a high rate of turnover, such as developing lymphocytes. In contrast, bcl-xL is found in tissues containing long-lived postmitotic cells, such as adult brain. Together these data suggest that bcl-x plays an important role in both positive and negative regulation of programmed cell death.

Discovery of a small molecule insulin mimetic with antidiabetic activity in mice

Insulin elicits a spectrum of biological responses by binding to its cell surface receptor. In a screen for small molecules that activate the human insulin receptor tyrosine kinase, a nonpeptidyl fungal metabolite (L-783,281) was identified that acted as an insulin mimetic in several biochemical and cellular assays. The compound was selective for insulin receptor versus insulin-like growth factor I (IGFI) receptor and other receptor tyrosine kinases. Oral administration of L-783,281 to two mouse models of diabetes resulted in significant lowering in blood glucose levels. These results demonstrate the feasibility of discovering novel insulin receptor activators that may lead to new therapies for diabetes.

Paracrine expression of a native soluble vascular endothelial growth factor receptor inhibits tumor growth, metastasis, and mortality rate

Vascular endothelial growth factor (VEGF) is a potent and selective vascular endothelial cell mitogen and angiogenic factor. VEGF expression is elevated in a wide variety of solid tumors and is thought to support their growth by enhancing tumor neovascularization. To block VEGF-dependent angiogenesis, tumor cells were transfected with cDNA encoding the native soluble FLT-1 (sFLT-1) truncated VEGF receptor which can function both by sequestering VEGF and, in a dominant negative fashion, by forming inactive heterodimers with membrane-spanning VEGF receptors. Transient transfection of HT-1080 human fibrosarcoma cells with a gene encoding sFLT-1 significantly inhibited their implantation and growth in the lungs of nude mice following i.v. injection and their growth as nodules from cells injected s.c. High sFLT-1 expressing stably transfected HT-1080 clones grew even slower as s.c. tumors. Finally, survival was significantly prolonged in mice injected intracranially with human glioblastoma cells stably transfected with the sflt-1 gene. The ability of sFLT-1 protein to inhibit tumor growth is presumably attributable to its paracrine inhibition of tumor angiogenesis in vivo, since it did not affect tumor cell mitogenesis in vitro. These results not only support VEGF receptors as antiangiogenic targets but also demonstrate that sflt-1 gene therapy might be a feasible approach for inhibiting tumor angiogenesis and growth.

Improved reporter strain for monitoring Cre recombinase-mediated DNA excisions in mice

Effective use of conditional Cre recombinase-loxP gene modification requires Cre-expressing mouse strains with defined patterns of expression. To assess the in vivo functionality of Cre-expressing mice, we have engineered an improved reporter strain for monitoring Cre-mediated excisions. The beta-galactosidase-neomycin phosphotransferase fusion gene (betageo)-trapped ROSA26 locus was modified by gene targeting such that betageo is expressed only after Cre-mediated excision of loxP-flanked DNA sequences. betageo from the excised ROSA26 allele is expressed ubiquitously in embryos and adult mice. By mating the reporter strain with Cre-expressing transgenic mice, we have shown that the loxP-flanked ROSA26 allele is accessible to Cre during early embryogenesis, as well as in a specific hematopoietic lineage (T lymphocytes). This improved reporter strain should facilitate monitoring in vivo Cre-mediated excision events in a variety of experimental contexts.

Dichloroacetate causes toxic neuropathy in MELAS: a randomized, controlled clinical trial

OBJECTIVE

To evaluate the efficacy of dichloroacetate (DCA) in the treatment of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS).

BACKGROUND

High levels of ventricular lactate, the brain spectroscopic signature of MELAS, correlate with more severe neurologic impairment. The authors hypothesized that chronic cerebral lactic acidosis exacerbates neuronal injury in MELAS and therefore, investigated DCA, a potent lactate-lowering agent, as potential treatment for MELAS.

METHODS

The authors conducted a double-blind, placebo-controlled, randomized, 3-year cross-over trial of DCA (25 mg/kg/day) in 30 patients (aged 10 to 60 years) with MELAS and the A3243G mutation. Primary outcome measure was a Global Assessment of Treatment Efficacy (GATE) score based on a health-related event inventory, and on neurologic, neuropsychological, and daily living functioning. Biologic outcome measures included venous, CSF, and 1H MRSI-estimated brain lactate. Blood tests and nerve conduction studies were performed to monitor safety.

RESULTS

During the initial 24-month treatment period, 15 of 15 patients randomized to DCA were taken off study medication, compared to 4 of 15 patients randomized to placebo. Study medication was discontinued in 17 of 19 patients because of onset or worsening of peripheral neuropathy. The clinical trial was terminated early because of peripheral nerve toxicity. The mean GATE score was not significantly different between treatment arms.

CONCLUSION

DCA at 25 mg/kg/day is associated with peripheral nerve toxicity resulting in a high rate of medication discontinuation and early study termination. Under these experimental conditions, the authors were unable to detect any beneficial effect. The findings show that DCA-associated neuropathy overshadows the assessment of any potential benefit in MELAS.

Activation of EGFP expression by Cre-mediated excision in a new ROSA26 reporter mouse strain

Reporter mouse strains are important tools for monitoring Cre recombinase-mediated excision in vivo. In practice, excision may be incomplete in a given population due to threshold level or variegated expression of Cre. Hence, it is desirable in many experimental contexts to isolate cells that have undergone excision to assess the consequences of gene ablation. To generate alternative reporter mice, an enhanced green fluorescent protein (EGFP) gene was targeted to the retroviral-trapped ROSA26 locus. Upon Cre-mediated excision of "Stop" sequences, EGFP was expressed ubiquitously during embryogenesis and in adult tissues (including T cells, B cells, and myeloid cells). Using this new reporter strain, separation of excised from nonexcised cells in vitro was achieved in thymocytes in a noninvasive manner based on activated EGFP expression. This new EGFP reporter strain should facilitate a variety of conditional gene-targeting experiments, including the functional studies of hematopoietic cells in lineage-specific knockout mice.

Cdc42 is required for PIP(2)-induced actin polymerization and early development but not for cell viability

BACKGROUND

Cdc42 and other Rho GTPases are conserved from yeast to humans and are thought to regulate multiple cellular functions by inducing coordinated changes in actin reorganization and by activating signaling pathways leading to specific gene expression. Direct evidence implicating upstream signals and components that regulate Cdc42 activity or for required roles of Cdc42 in activation of downstream protein kinase signaling cascades is minimal, however. Also, whereas genetic analyses have shown that Cdc42 is essential for cell viability in yeast, its potential roles in the growth and development of mammalian cells have not been directly assessed.

RESULTS

To elucidate potential functions of Cdc42 mammalian cells, we used gene-targeted mutation to inactivate Cdc42 in mouse embryonic stem (ES) cells and in the mouse germline. Surprisingly, Cdc42-deficient ES cells exhibited normal proliferation and phosphorylation of mitogen- and stress-activated protein kinases. Yet Cdc42 deficiency caused very early embryonic lethality in mice and led to aberrant actin cytoskeletal organization in ES cells. Moreover, extracts from Cdc42-deficient cells failed to support phosphatidylinositol 4,5-bisphosphate (PIP(2))-induced actin polymerization.

CONCLUSIONS

Our studies clearly demonstrate that Cdc42 mediates PIP(2)-induced actin assembly, and document a critical and unique role for Cdc42 in this process. Moreover, we conclude that, unexpectedly, Cdc42 is not necessary for viability or proliferation of mammalian early embryonic cells. Cdc42 is, however, absolutely required for early mammalian development.

Quantitative objective markers for upper and lower motor neuron dysfunction in ALS

OBJECTIVE

To investigate the value of objective biomarkers for upper (UMN) and lower (LMN) motor neuron involvement in ALS.

METHODS

We prospectively studied 64 patients with ALS and its subsets using clinical measures, proton MR spectroscopic imaging ((1)H MRSI), diffusion tensor imaging, transcranial magnetic stimulation, and the motor unit number estimation (MUNE) at baseline and every 3 months for 15 months and compared them with control subjects.

RESULTS

(1)H MRSI measures of the primary motor cortex N-acetyl-aspartate (NAA) concentration were markedly reduced in ALS (p = 0.009) and all UMN syndromes combined (ALS, familial ALS [fALS], and primary lateral sclerosis; p = 0.03) vs control values. Central motor conduction time to the tibialis anterior was prolonged in ALS (p < 0.0005) and combined UMN syndromes (p = 0.001). MUNE was lower in ALS (p < 0.0005) and all LMN syndromes combined (ALS, fALS, and progressive muscular atrophy; p = 0.001) vs controls. All objective markers correlated well with the ALS Functional Rating Scale-Revised, finger and foot tapping, and strength testing, suggesting these markers related to disease activity. Regarding changes over time, MUNE changed rapidly, whereas neuroimaging markers changed more slowly and did not significantly differ from baseline.

CONCLUSIONS

(1)H MR spectroscopic imaging measures of the primary motor cortex N-acetyl-aspartate (NAA) concentration and ratio of NAA to creatine, central motor conduction time to the tibialis anterior, and motor unit number estimation significantly differed between ALS, its subsets, and control subjects, suggesting they have potential to provide insight into the pathobiology of these disorders.

Baicalin attenuates global cerebral ischemia/reperfusion injury in gerbils via anti-oxidative and anti-apoptotic pathways

Baicalin is an important medicinal herb purified from the dry roots of Scutellaria baicalensis Georgi. The present study was undertaken to evaluate the neuroprotective effects of baicalin in gerbils subjected to transient global cerebral ischemic-reperfusion injury. Baicalin at doses of 50, 100 and 200mg/kg was intraperitoneally injected into the gerbils immediately after cerebral ischemia. Seven days after reperfusion, hematoxylin and eosin (HE) staining was performed to analyze hippocampal CA1 pyramidal damage histopathologically. In addition, in order to understand the potential protective mechanism of baicalin, we examined anti-oxidative enzymes, such superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), non-enzymatic scavenger glutathione (GSH) and measured the content of malondialdehyde (MDA) in hippocampus. The mRNA and protein expressions of BDNF were determined in ischemic hippocampus by real-time RT-PCR and Western blot, respectively. Evidence for neuronal apoptosis was detected by real-time RT-PCR, Western blot and caspase-3 activity measurement. Histopathological examination showed that the administration of baicalin by the dose of 100 and 200mg/kg significantly attenuated ischemia-induced neuronal cell damage. Reduced level of MDA, obviously elevated activities of SOD and GSH as well as GSH-PX were also found in baicalin-treated groups. Further investigation demonstrated that treatment with baicalin remarkably promoted the expression of BDNF and inhibited the expression of caspase-3 at mRNA and protein levels by real-time RT-PCR and Western blot, respectively. Besides, caspase-3 activity assay also elucidated that the administration of baicalin could significantly suppress caspase-3 in ischemic gerbils hippocampus. Theses findings suggest that baicalin's neuroprotection appears to be associated with its anti-oxidative and anti-apoptotic properties in global cerebral ischemia in the gerbils.

Cerebral lactic acidosis correlates with neurological impairment in MELAS

OBJECTIVE

To evaluate the role of chronic cerebral lactic acidosis in mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS).

METHODS

The authors studied 91 individuals from 34 families with MELAS and the A3243G point mutation and 15 individuals from two families with myoclonus epilepsy and ragged red fibers (MERRF) and the A8344G mutation. Subjects were divided into four groups. Paternal relatives were studied as controls (Group 1). The maternally related subjects were divided clinically into three groups: asymptomatic (no clinical evidence of neurologic disease) (Group 2), oligosymptomatic (neurologic symptoms but without the full clinical picture of MELAS or MERRF) (Group 3), and symptomatic (fulfilling MELAS or MERRF criteria) (Group 4). The authors performed a standardized neurologic examination, neuropsychological testing, MRS, and leukocyte DNA analysis in all subjects.

RESULTS

The symptomatic and oligosymptomatic MELAS subjects had significantly higher ventricular lactate than the other groups. There was a significant correlation between degree of neuropsychological and neurologic impairment and cerebral lactic acidosis as estimated by ventricular MRS lactate levels.

CONCLUSIONS

High levels of ventricular lactate, the brain spectroscopic signature of MELAS, are associated with more severe neurologic impairment.

The LIM-domain binding protein Ldb1 and its partner LMO2 act as negative regulators of erythroid differentiation

The nuclear LIM domain protein LMO2, a T cell oncoprotein, is essential for embryonic erythropoiesis. LIM-only proteins are presumed to act primarily through protein-protein interactions. We, and others, have identified a widely expressed protein, Ldb1, whose C-terminal 76-residues are sufficient to mediate interaction with LMO2. In murine erythroleukemia cells, the endogenous Lbd1 and LMO2 proteins exist in a stable complex, whose binding affinity appears greater than that between LMO2 and the bHLH transcription factor SCL. However, Ldb1, LMO2, and SCL/E12 can assemble as a multiprotein complex on a consensus SCL binding site. Like LMO2, the Ldb1 gene is expressed in fetal liver and erythroid cell lines. Forced expression of Ldb1 in G1ER proerythroblast cells inhibited cellular maturation, a finding compatible with the decrease in Ldb1 gene expression that normally occurs during erythroid differentiation. Overexpression of the LMO2 gene also inhibited erythroid differentiation. Our studies demonstrate a function for Ldb1 in hemopoietic cells and suggest that one role of the Ldb1/LMO2 complex is to maintain erythroid precursors in an immature state.

Molecular cytogenetic analysis of cutaneous T-cell lymphomas: identification of common genetic alterations in Sézary syndrome and mycosis fungoides

BACKGROUND

Data on genome-wide surveys for chromosome aberrations in primary cutaneous T-cell lymphoma (CTCL) are limited.

OBJECTIVE

To investigate genetic aberrations in CTCL.

METHODS

We analysed 18 cases of Sézary syndrome (SS) and 16 cases of mycosis fungoides (MF) by comparative genomic hybridization (CGH) analysis, and correlated findings with the results of additional conventional cytogenetics, fluorescent in situ hybridization (FISH) and allelotyping studies.

RESULTS

CGH analysis showed chromosome imbalances (CIs) in 19 of 34 CTCL cases (56%). The mean +/- SD number of CIs per sample was 1.8 +/- 2.4, with losses (1.2 +/- 2.0) slightly more frequent than gains (0.6 +/- 1.0). The most frequent losses involved chromosomes 1p (38%), 17p (21%), 10q/10 (15%) and 19 (15%), with minimal regions of deletion at 1p31p36 and 10q26. The commonly detected chromosomal gains involved 4/4q (18%), 18 (15%) and 17q/17 (12%). Both SS and late stages of MF showed a similar pattern of CIs, but no chromosomal changes were found in three patients with T1 stage MF. Of the 18 SS cases also analysed by cytogenetics, seven showed clonal chromosome abnormalities (39%). Five cases had structural aberrations affecting chromosomes 10 and 17, four demonstrated rearrangement of 1p and three revealed an abnormality of either 6q or 14q consistent with CGH findings. FISH analysis showed chromosome 1p and 17q rearrangements in five of 15 SS cases, and chromosome 10 abnormalities in four SS cases consistent with both the G-banded karyotype and the CGH results. In addition, allelotyping analysis of 33 MF patients using chromosome 1 markers suggested minimal regions of deletion at D1S228 (1p36), D1S2766 (1p22) and D1S397 (1q25).

CONCLUSIONS

These findings provide a comprehensive assessment of genetic abnormalities in CTCL and a rational approach for further studies.

Natural history of MELAS associated with mitochondrial DNA m.3243A>G genotype

OBJECTIVE

To describe the natural history of clinical and laboratory features associated with the m.3243A>G mitochondrial DNA point mutation. Natural history data are needed to obtain prognostic information and for clinical trial planning.

METHODS

We included 85 matrilineal relatives from 35 families with at least 2 visits in this prospective cohort study. Thirty-one were fully symptomatic with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), and 54 were carrier relatives. Evaluations included standardized questionnaires (medical history and daily living functioning), physical examination, neuropsychological testing, and a battery of imaging and laboratory tests. We evaluated changes in clinical and laboratory features over time and survival. Outcomes are reported over a follow-up period of up to 10.6 years (mean 3.8 ± 2.2 years for patients and 5.5 ± 3.0 for carrier relatives).

RESULTS

Neurologic examination, neuropsychological testing, and daily living scores significantly declined in all patients with MELAS, whereas no significant deterioration occurred in carrier relatives. Cerebral MRI scores declined significantly in patients with MELAS. Magnetic resonance spectroscopy estimates of lactate in the lateral ventricles increased over time, and high lactate was associated with increased mortality. Symptom onset in childhood often was associated with worse outcome. Patients with MELAS had a greater death rate than carrier relatives.

CONCLUSIONS

Patients with MELAS carrying the m.3243A>G mutation show a measurable decline in clinical and imaging outcomes. It is hoped that these data will be helpful in anticipating the disease course and in planning clinical trials for MELAS.

Chromatographic separation of proteins on metal immobilized iminodiacetic acid-bound molded monolithic rods of macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate)

Continuous rod of macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate) was prepared by a free radical polymerization within the confines of a stainless-steel column. The epoxide groups of the rod were modified by a reaction with iminodiacetic acid (IDA) that affords the active site to form metal IDA chelates used for immobilized metal affinity chromatography (IMAC). The efficiency of coupling of IDA to the epoxide-contained matrix was studied as a function of reaction time and temperature. High-performance separation of proteins, based on immobilized different metals on the column, were described. The influence of pH on the adsorption capacity of bovine serum albumin on the Cu2+-IDA continuous rod column was investigated in the range from 5.0 to 9.0. Purification of lysozyme from egg white and human serum albumin (HSA) on the commercially available HSA solution were performed on the naked IDA and Cu2+-IDA continuous rod columns, respectively; and the purity of the obtained fractions was detected by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry.

FruA, a putative transcription factor essential for the development of Myxococcus xanthus

A new developmental gene, fruA, of Myxococcus xanthus was cloned using a one-step cloning vector, TnV. DNA sequencing of the wild-type allele of the fruA gene indicated that the fruA gene encodes a protein of 229 amino acid residues with a calculated molecular weight of 24672. The deduced amino acid sequence of FruA protein showed similarity to those of many bacterial regulatory proteins carrying a DNA-binding helix-turn-helix motif. The transcription-initiation site of the fruA gene was determined by a primer-extension experiment. Development of M. xanthus cells with a disrupted fruA gene stopped at the stage of mound formation. Although cells were able to aggregate to form mounds, myxospores were not formed. By Northern and Western blot analysis, it was found that the fruA expression was not detected during vegetative growth but initiated at around 6 h and reached the highest level at 12 h after the onset of development. Expression of the fruA gene was dependent on the expression of asg, bsg, csg, dsg, and esg genes, indicating that a series of intercellular signalling is necessary for the expression of the fruA gene. The effects of the fruA mutation on beta-galactosidase expression of various developmentally regulated genes fused with the lacZ gene were analysed; three developmental lacZ fusions (omega 4469, omega 4273 and omega 4500) were either poorly induced or not induced at all, while three other lacZ fusions (omega 4408, omega 4521 and omega 4455) expressed at the early stage of development were normally induced but were unable to be repressed at a later stage of development as in the wild-type strain. Interestingly, in the fruA mutant, tps (the gene for protein S) was not activated. From these results together with analysis of the amino acid sequence of FruA, we propose that FruA is a putative transcription factor required for the development of M.xanthus.

Interleukin-37 ameliorates myocardial ischaemia/reperfusion injury in mice

Innate immune and inflammatory responses are involved in myocardial ischaemia/reperfusion (I/R) injury. Interleukin (IL)-37 is a newly identified member of the IL-1 family, and functions as a fundamental inhibitor of innate immunity and inflammation. However, its role in myocardial I/R injury remains unknown. I/R or sham operations were performed on male C57BL/6J mice. I/R mice received an injection of recombinant human IL-37 or vehicle, immediately before reperfusion. Compared with vehicle treatment, mice treated with IL-37 showed an obvious amelioration of the I/R injury, as demonstrated by reduced infarct size, decreased cardiac troponin T level and improved cardiac function. This protective effect was associated with the ability of IL-37 to suppress production of proinflammatory cytokines, chemokines and neutrophil infiltration, which together contributed to a decrease in cardiomyocyte apoptosis and reactive oxygen species (ROS) generation. In addition, we found that IL-37 inhibited the up-regulation of Toll-like receptor (TLR)-4 expression and nuclear factor kappa B (NF-kB) activation after I/R, while increasing the anti-inflammatory IL-10 level. Moreover, the administration of anti-IL-10R antibody abolished the protective effects of IL-37 in I/R injury. In-vitro experiments further demonstrated that IL-37 protected cardiomyocytes from apoptosis under I/R condition, and suppressed the migration ability of neutrophils towards the chemokine LIX. In conclusion, IL-37 plays a protective role against mouse myocardial I/R injury, offering a promising therapeutic medium for myocardial I/R injury.

Neuroprotection by dehydroepiandrosterone-sulfate: role of an NFkappaB-like factor

Levels of dehydroepiandrosterone (DHEA) and its sulfated derivative (DHEA-S) decline during aging and reach even lower levels in Alzheimer's disease (AD). Previously published effects of DHEA and DHEA-S on unchallenged neuronal survival led us to test them in an excitotoxicity paradigm. While DHEA-S protected hippocampal neurons against glutamate, little protection was observed with equivalent doses of DHEA itself. This differential neuroprotection was consistent with the ability of DHEA-S (but not DHEA) to elevate a kappaB-dependent transcription factor activity, a phenomenon we previously have connected with neuroprotection. Furthermore, suppression of kappaB DNA-binding by 'decoy' oligonucleotides blocked the neuroprotective activity of DHEA-S. These findings imply that age-related declines in the availability of DHEA-S could exacerbate neurotoxicity, and the data suggest that therapeutic gains may be obtained with pharmacological manipulation of kappaB-dependent transcription in neurons.

Vascular endothelial growth factor receptor KDR tyrosine kinase activity is increased by autophosphorylation of two activation loop tyrosine residues

Vascular endothelial growth factor is an important physiological regulator of angiogenesis. The function of this endothelial cell selective growth factor is mediated by two homologous tyrosine kinase receptors, fms-like tyrosine kinase 1 (Flt-1) and kinase domain receptor (KDR). Although the functional consequence of vascular endothelial growth factor binding to the Flt-1 receptor is not fully understood, it is well established that mitogenic signaling is mediated by KDR. Upon sequencing several independent cDNA clones spanning the cytoplasmic region of human KDR, we identified and confirmed the identity of a functionally required valine at position 848 in the ATP binding site, rather than the previously reported glutamic acid residue, which corresponds to an inactive tyrosine kinase. The cytoplasmic domain of recombinant native KDR, expressed as a glutathione S-transferase fusion protein, can undergo autophosphorylation in the presence of ATP. In addition, the kinase activity can be substantially increased by autophosphorylation at physiologic ATP concentrations. Mutation analysis indicates that both tyrosine residues 1054 and 1059 are required for activation, which is a consequence of an increased affinity for both ATP and the peptide substrate and has no effect on kcat, the intrinsic catalytic activity of the enzyme. KDR kinase catalyzes phosphotransfer by formation of a ternary complex with ATP and the peptide substrate. We demonstrate that tyrosine kinase antagonists can preferentially inhibit either the unactivated or activated form of the enzyme.

Yeast mRNA cap methyltransferase is a 50-kilodalton protein encoded by an essential gene

RNA (guanine-7-)methyltransferase, the enzyme responsible for methylating the 5' cap structure of eukaryotic mRNA, was isolated from extracts of Saccharomyces cerevisiae. The yeast enzyme catalyzed methyl group transfer from S-adenosyl-L-methionine to the guanosine base of capped, unmethylated poly(A). Cap methylation was stimulated by low concentrations of salt and was inhibited by S-adenosyl-L-homocysteine, a presumptive product of the reaction, but not by S-adenosyl-D-homocysteine. The methyltransferase sedimented in a glycerol gradient as a single discrete component of 3.2S. A likely candidate for the gene encoding yeast cap methyltransferase was singled out on phylogenetic grounds. The ABD1 gene, located on yeast chromosome II, encodes a 436-amino-acid (50-kDa) polypeptide that displays regional similarity to the catalytic domain of the vaccinia virus cap methyltransferase. That the ABD1 gene product is indeed RNA (guanine-7-)methyltransferase was established by expressing the ABD1 protein in bacteria, purifying the protein to homogeneity, and characterizing the cap methyltransferase activity intrinsic to recombinant ABD1. The physical and biochemical properties of recombinant ABD1 methyltransferase were indistinguishable from those of the cap methyltransferase isolated and partially purified from whole-cell yeast extracts. Our finding that the ABD1 gene is required for yeast growth provides the first genetic evidence that a cap methyltransferase (and, by inference, the cap methyl group) plays an essential role in cellular function in vivo.

Accelerated mRNA decay in conditional mutants of yeast mRNA capping enzyme

Current models of mRNA decay in yeast posit that 3' deadenylation precedes enzymatic removal of the 5' cap, which then exposes the naked end to 5' exonuclease action. Here, we analyzed gene expression in Saccharomyces cerevisiae cells bearing conditional mutations of Ceg1 (capping enzyme), a 52 kDa protein that transfers GMP from GTP to the 5' end of mRNA to form the GpppN cap structure. Shift of ceg1 mutants to restrictive temperature elicited a rapid decline in the rate of protein synthesis, which correlated with a sharp reduction in the steady-state levels of multiple individual mRNAs. ceg1 mutations prevented the accumulation of SSA1 and SSA4 mRNAs that were newly synthesized at the restrictive temperature. Uncapped poly(A)+ SSA4 mRNA accumulated in cells lacking the 5' exoribonuclease Xrn1. These findings provide genetic evidence for the long-held idea that the cap guanylate is critical for mRNA stability. The deadenylation-decapping-degradation pathway appears to be short-circuited when Ceg1 is inactivated.

Motor cortex glutathione deficit in ALS measured in vivo with the J-editing technique

This study compared in vivo levels of the antioxidant glutathione (GSH) in the motor cortex of 11 ALS patients with those in 11 age-matched healthy volunteers (HV). Using the standard J-edited spin-echo difference MRS technique, GSH spectra were recorded on a 3.0 T GE MR system from a single precentral gyrus voxel. GSH levels expressed as ratios to the unsuppressed voxel tissue water (W) were 31% lower in ALS patients than in HV (p=.005), and 36% lower in ALS than in HV (p=.02) when expressed as ratios to the total creatine peak (tCr), supporting a role for oxidative stress in ALS. Levels of the putative neuronal marker N-acetylaspartate (NAA) relative to W did not differ between ALS and HV (p=.26), but were lower by 9% in ALS than in HV (p=.013) when expressed as ratios relative to tCr. This discrepancy is attributed to small but opposite changes in NAA and tCr in ALS that, as a ratio, resulted in a statistically significant group difference, further suggesting caution in using tCr as an internal reference under pathological conditions.

Solution structure of the ets domain of Fli-1 when bound to DNA

Members of the ets family of transcription factors share a conserved DNA-binding domain, the ets domain. By using multidimensional NMR, we have determined the structure of the ets domain of human Fli-1 in the DNA-bound form. It consists of three alpha-helices and a four-stranded beta-sheet, similar to structures of the class of helix-turn-helix DNA binding proteins first found in the catabolite activator protein of Escherichia coli. NMR and mutagenesis experiments suggest that in comparison to structurally related proteins, the ets domain uses a new variation of the helix-turn-helix motif for binding to DNA.

Neurological deterioration in late infantile neuronal ceroid lipofuscinosis

BACKGROUND

Late infantile neuronal ceroid lipofuscinosis (LINCL) is associated with progressive degeneration of the brain and retina starting in early childhood.

METHODS

Thirty-two individual neurologic, ophthalmologic, and CNS imaging (MRI and MRS) assessments of 18 children with LINCL were analyzed. Disease severity was followed by two rating scales, one previously established but modified to solely assess the brain and exclude the retinal disease (modified Hamburg LINCL scale), and a newly developed scale, with expanded evaluation of the CNS impairment (Weill Cornell LINCL scale).

RESULTS

For the 18 children, the Weill Cornell scale yielded a closer correlation with both age and time since initial clinical manifestation of the disease than did the modified Hamburg scale. There were no significant differences as a function of age or time since initial manifestation of the disease in the rating scales among the most frequent CLN2 mutations (G3556C, 56% of all alleles or C3670T, 22% of all alleles). Measurements of cortical MRS N-acetyl-aspartate content, MRI ventricular, gray matter and white matter volume, and cortical apparent diffusion coefficient correlated to a variable degree with the age of the children and the time since initial clinical manifestation of the disease. All imaging measurements correlated better with the Weill Cornell CNS scale compared to the modified Hamburg LINCL scale.

CONCLUSION

The data suggest that the Weill Cornell late infantile neuronal ceroid lipofuscinosis (LINCL) scale, together with several of the MRI measurements, may be useful in the assessment of severity and progression of LINCL and for the evaluation of novel therapeutic strategies.