The detection of DNA-binding proteins by protein blotting

A method, called "protein blotting," for the detection of DNA-binding proteins is described. Proteins are separated on an SDA-polyacrylamide gel. The gel is sandwiched between 2 nitrocellulose filters and the proteins allowed to diffuse out of the gel and onto the filters. The proteins are tightly bound to each filter, producing a replica of the original gel pattern. The replica is used to detect DNA-binding proteins, RNA-binding proteins or histone-binding proteins by incubation of the filter with [32P]DNA, [125I]RNA, or [125I] histone. Evidence is also presented that specific protein-DNA interactions may be detected by this technique; under appropriate conditions, the lac repressor binds only to DNA containing the lac operator. Strategies for the detection of specific protein-DNA interactions are discussed.

The myb-homologous P gene controls phlobaphene pigmentation in maize floral organs by directly activating a flavonoid biosynthetic gene subset

The maize P gene, which specifies red pigmentation of the kernel pericarp, cob, and other floral organs, has been an important model since the early days of modern genetics. Here we show that P encodes a Myb homolog that recognizes the sequence CCT/AACC, in sharp contrast with the C/TAACGG bound by vertebrate Myb proteins. P binds to and activates transcription of the A1 gene required for 3-deoxy flavonoid and phlobaphene biosynthesis, but not the Bz1 gene required for anthocyanin biosynthesis. The maize C1 gene, which also encodes a Myb homolog, activates both the A1 and Bz1 genes, but only in the presence of a basic-helix-loop-helix coactivator encoded by the maize genes R or B. These results indicate that Myb homologs can differentially regulate gene expression by binding different DNA sequences, through combinatorial interactions with other factors, or both.

Identification of the residues in the Myb domain of maize C1 that specify the interaction with the bHLH cofactor R

The maize Myb transcription factor C1 depends on the basic helix-loop-helix (bHLH) proteins R or B for regulatory function, but the closely related Myb protein P does not. We have used the similarity between the Myb domains of C1 and P to identify residues that specify the interaction between the Myb domain of C1 and the N-terminal region of R. Substitution of four predicted solvent-exposed residues in the first helix of the second Myb repeat of P with corresponding residues from C1 is sufficient to confer on P the ability to physically interact with R. However, two additional Myb domain amino acid changes are needed to make the P regulatory activity partially dependent on R in maize cells. Interestingly, when P is altered so that it interacts with R, it can activate the Bz1 promoter, normally regulated by C1 + R but not by P. Together, these findings demonstrate that the change of a few amino acids within highly similar Myb domains can mediate differential interactions with a transcriptional coregulator that plays a central role in the regulatory specificity of C1, and that Myb domains play important roles in combinatorial transcriptional regulation.

Multiple regulators of Ty1 transposition in Saccharomyces cerevisiae have conserved roles in genome maintenance

Most Ty1 retrotransposons in the genome of Saccharomyces cerevisiae are transpositionally competent but rarely transpose. We screened yeast mutagenized by insertion of the mTn3-lacZ/LEU2 transposon for mutations that result in elevated Ty1 cDNA-mediated mobility, which occurs by cDNA integration or recombination. Here, we describe the characterization of mTn3 insertions in 21 RTT (regulation of Ty1 transposition) genes that result in 5- to 111-fold increases in Ty1 mobility. These 21 RTT genes are EST2, RRM3, NUT2, RAD57, RRD2, RAD50, SGS1, TEL1, SAE2, MED1, MRE11, SCH9, KAP122, and 8 previously uncharacterized genes. Disruption of RTT genes did not significantly increase Ty1 RNA levels but did enhance Ty1 cDNA levels, suggesting that most RTT gene products act at a step after mRNA accumulation but before cDNA integration. The rtt mutations had widely varying effects on integration of Ty1 at preferred target sites. Mutations in RTT101 and NUT2 dramatically stimulated Ty1 integration upstream of tRNA genes. In contrast, a mutation in RRM3 increased Ty1 mobility >100-fold without increasing integration upstream of tRNA genes. The regulation of Ty1 transposition by components of fundamental pathways required for genome maintenance suggests that Ty1 and yeast have coevolved to link transpositional dormancy to the integrity of the genome.

Engineering secondary metabolism in maize cells by ectopic expression of transcription factors

Manipulation of plant natural product biosynthesis through genetic engineering is an attractive but technically challenging goal. Here, we demonstrate that different secondary metabolites can be produced in cultured maize cells by ectopic expression of the appropriate regulatory genes. Cell lines engineered to express the maize transcriptional activators C1 and R accumulate two cyanidin derivatives, which are similar to the predominant anthocyanin found in differentiated plant tissues. In contrast, cell lines that express P accumulate various 3-deoxy flavonoids. Unexpectedly, P-expressing cells in culture also accumulate phenylpropanoids and green fluorescent compounds that are targeted to different subcellular compartments. Two endogenous biosynthetic genes (c2 and a1, encoding chalcone synthase and flavanone/dihydroflavonol reductase, respectively) are independently activated by ectopic expression of either P or C1/R, and there is a dose-response relationship between the transcript level of P and the degree to which c2 or a1 is expressed. Our results support a simple model showing how the gene encoding P may act as a quantitative trait locus controlling insecticidal C-glycosyl flavone level in maize silks, and they suggest how p1 might confer a selective advantage against insect predation in maize.

Targeted manipulation of maize genes in vivo using chimeric RNA/DNA oligonucleotides

Site-specific heritable mutations in maize genes were engineered by introducing chimeric RNA/DNA oligonucleotides. Two independent targets within the endogenous maize acetohydroxyacid synthase gene sequence were modified in a site-specific fashion, thereby conferring resistance to either imidazolinone or sulfonylurea herbicides. Similarly, an engineered green fluorescence protein transgene was site-specifically modified in vivo. Expression of the introduced inactive green fluorescence protein was restored, and plants containing the modified transgene were regenerated. Progeny analysis indicated Mendelian transmission of the converted transgene. The efficiency of gene conversion mediated by chimeric oligonucleotides in maize was estimated as 10(-4), which is 1-3 orders of magnitude higher than frequencies reported for gene targeting by homologous recombination in plants. The heritable changes in maize genes engineered by this approach create opportunities for basic studies of plant gene function and agricultural trait manipulation and also provide a system for studying mismatch repair mechanisms in maize.

Expression profiling of the maize flavonoid pathway genes controlled by estradiol-inducible transcription factors CRC and P

To determine the scope of gene expression controlled by the maize transcription factors C1/R and P, which are responsible for activating flavonoid synthesis, we used GeneCalling, an open-ended, gel-based, mRNA-profiling technology, to analyze cell suspension lines of the maize inbred Black Mexican Sweet (BMS) that harbored estradiol-inducible versions of these factors. BMS cells were transformed with a continually expressed estrogen receptor/maize C1 activator domain fusion gene (ER-C1) and either a fusion of C1 and R (CRC), P, or luciferase genes regulated by a promoter containing four repeats of an estrogen receptor binding site. Increasing amounts of luciferase activity, anthocyanins, and flavan-4-ols were detected in the respective cell lines after the addition of estradiol. The expression of both known and novel genes was detected simultaneously in these BMS lines by profiling the mRNA isolated from replicate samples at 0, 6, and 24 hr after estradiol treatment. Numerous cDNA fragments were identified that showed a twofold or greater difference in abundance at 6 and 24 hr than at 0 hr. The cDNA fragments from the known flavonoid genes, except chalcone isomerase (chi1), were induced in the CRC-expressing line after hormone induction, whereas only the chalcone synthase (c2) and flavanone/dihydroflavonol reductase (a1) genes were induced in the P-expressing line, as was expected. Many novel cDNA fragments were also induced or repressed by lines expressing CRC alone, P alone, or both transcription factors in unique temporal patterns. The temporal differences and the evidence of repression indicate a more diverse set of regulatory controls by CRC or P than originally expected. GeneCalling analysis was successful in detecting members of complex metabolic pathways and uncovering novel genes that were either coincidentally regulated or directly involved in such pathways.

Three-dimensional microscopy of the Rad51 recombination protein during meiotic prophase

An open question in meiosis is whether the Rad51 recombination protein functions solely in meiotic recombination or whether it is also involved in the chromosome homology search. To address this question, we have performed three-dimensional high-resolution immunofluorescence microscopy to visualize native Rad51 structures in maize male meiocytes. Maize has two closely related RAD51 genes that are expressed at low levels in differentiated tissues and at higher levels in mitotic and meiotic tissues. Cells and nuclei were specially fixed and embedded in polyacrylamide to maintain both native chromosome structure and the three dimensionality of the specimens. Analysis of Rad51 in maize meiocytes revealed that when chromosomes condense during leptotene, Rad51 is diffuse within the nucleus. Rad51 foci form on the chromosomes at the beginning of zygotene and rise to approximately 500 per nucleus by mid-zygotene when chromosomes are pairing and synapsing. During chromosome pairing, we consistently found two contiguous Rad51 foci on paired chromosomes. These paired foci may identify the sites where DNA sequence homology is being compared. During pachytene, the number of Rad51 foci drops to seven to 22 per nucleus. This higher number corresponds approximately to the number of chiasmata in maize meiosis. These observations are consistent with a role for Rad51 in the homology search phase of chromosome pairing in addition to its known role in meiotic recombination.

Genome-wide transcript analysis of maize hybrids: allelic additive gene expression and yield heterosis

Heterosis, or hybrid vigor, has been widely exploited in plant breeding for many decades, but the molecular mechanisms underlying the phenomenon remain unknown. In this study, we applied genome-wide transcript profiling to gain a global picture of the ways in which a large proportion of genes are expressed in the immature ear tissues of a series of 16 maize hybrids that vary in their degree of heterosis. Key observations include: (1) the proportion of allelic additively expressed genes is positively associated with hybrid yield and heterosis; (2) the proportion of genes that exhibit a bias towards the expression level of the paternal parent is negatively correlated with hybrid yield and heterosis; and (3) there is no correlation between the over- or under-expression of specific genes in maize hybrids with either yield or heterosis. The relationship of the expression patterns with hybrid performance is substantiated by analysis of a genetically improved modern hybrid (Pioneer hybrid 3394) versus a less improved older hybrid (Pioneer hybrid 3306) grown at different levels of plant density stress. The proportion of allelic additively expressed genes is positively associated with the modern high yielding hybrid, heterosis and high yielding environments, whereas the converse is true for the paternally biased gene expression. The dynamic changes of gene expression in hybrids responding to genotype and environment may result from differential regulation of the two parental alleles. Our findings suggest that differential allele regulation may play an important role in hybrid yield or heterosis, and provide a new insight to the molecular understanding of the underlying mechanisms of heterosis.

Massively parallel signature sequencing (MPSS) as a tool for in-depth quantitative gene expression profiling in all organisms

Massively parallel signature sequencing (MPSS) is one of the newest tools available for conducting in-depth expression profiling. MPSS is an open-ended platform that analyses the level of expression of virtually all genes in a sample by counting the number of individual mRNA molecules produced from each gene. There is no requirement that genes be identified and characterised prior to conducting an experiment. MPSS has a routine sensitivity at a level of a few molecules of mRNA per cell, and the datasets are in a digital format that simplifies the management and analysis of the data. Therefore, of the various microarray and non-microarray technologies currently available, MPSS provides many advantages for generating the type of complete datasets that will help to facilitate hypothesis-driven experiments in the era of digital biology.

Maize R2R3 Myb genes: Sequence analysis reveals amplification in the higher plants

Transcription factors containing the Myb-homologous DNA-binding domain are widely found in eukaryotes. In plants, R2R3 Myb-domain proteins are involved in the control of form and metabolism. The Arabidopsis genome harbors >100 R2R3 Myb genes, but few have been found in monocots, animals, and fungi. Using RT-PCR from different maize organs, we cloned 480 fragments corresponding to a 42-44 residue-long sequence spanning the region between the conserved DNA-recognition helices (Myb(BRH)) of R2R3 Myb domains. We determined that maize expresses >80 different R2R3 Myb genes, and evolutionary distances among maize Myb(BRH) sequences indicate that most of the amplification of the R2R3 Myb gene family occurred after the origin of land plants but prior to the separation of monocots and dicots. In addition, evidence is provided for the very recent duplication of particular classes of R2R3 Myb genes in the grasses. Together, these findings render a novel line of evidence for the amplification of the R2R3 Myb gene family in the early history of land plants and suggest that maize provides a possible model system to examine the hypothesis that the expansion of Myb genes is associated with the regulation of novel plant cellular functions.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Complementary studies of the gastrointestinal safety of the cyclo-oxygenase-2-selective inhibitor etoricoxib

BACKGROUND

Cyclo-oxygenase-2-selective non-steroidal anti-inflammatory drugs are intended to preserve cyclo-oxygenase-1-mediated gastroprotection and platelet function, whilst inhibiting cyclo-oxygenase-2-mediated inflammation.

AIM

To assess the gastrointestinal safety of the cyclo-oxygenase-2-selective inhibitor etoricoxib vs. non-selective non-steroidal anti-inflammatory drugs.

METHODS

Two randomized, double-blind, placebo- and active-controlled studies were performed: (i) daily faecal red blood cell loss was measured in 62 subjects receiving etoricoxib (120 mg once daily), ibuprofen (800 mg t.d.s.) or placebo for 28 days; (ii) the incidence of endoscopically detectable gastric/duodenal ulcers was determined in 742 osteoarthritis or rheumatoid arthritis patients receiving etoricoxib (120 mg once daily), naproxen (500 mg b.d.) or placebo over 12 weeks.

RESULTS

In the first study, the between-treatment ratio of faecal blood loss for etoricoxib vs. placebo (1.06) was not significantly different from unity; however, the ratios for ibuprofen vs. placebo (3.26) and etoricoxib (3.08) were significantly greater than unity (P < 0.001). In the second study, the incidence of ulcers of > or = 3 mm with naproxen (25.3%) was significantly higher than that with etoricoxib (7.4%) or placebo (1.4%; P < 0.001); the results were similar for ulcers of > or = 5 mm.

CONCLUSIONS

The reduced toxicity of etoricoxib (less faecal blood loss and fewer endoscopically detectable lesions) suggests that use of this drug will may be associated with a reduced incidence of gastrointestinal perforations, ulcers and bleeds.

A regulatory gene as a novel visible marker for maize transformation

The temporal and spatial patterns of anthocyanin pigmentation in the maize plant are determined by the presence or absence of the R protein product, a presumed transcriptional activator. At least 50 unique patterns of pigmentation, conditioned by members of the R gene family, have been described. In this study, microprojectiles were used to introduce into maize cells a vector containing the transcription unit from one of these genes (Lc) fused to a constitutive promoter. This chimeric gene induces cell autonomous pigmentation in tissues that are not normally pigmented by the Lc gene. As a reporter for gene expression studies in maize, R is unique because it can be quantified in living tissue simply by counting the number of pigmented cells following bombardment. R may also be useful as a visible marker for selecting stably transformed cell lineages that can give rise to transgenic plants.

A review of the reported defects in the human C1 esterase inhibitor gene producing hereditary angioedema including four new mutations

C1 esterase inhibitor (C1INH) is an important regulatory protein of the classical pathway of complement. Mutations in the gene for this protein cause the autosomal dominant disorder hereditary angioedema (HAE). Approximately 85% of patients with HAE have a Type I defect, characterized by a diminished level of antigenic and functional C1INH. Patients with Type II defects have sufficient protein, but one allele produces dysfunctional protein. We have sequenced the DNA from HAE patients and have discovered four previously unreported mutations. The first mutation is a splice site error at nucleotide 8721, which changes the 3' acceptor splice site AG to GG at the end of intron 5 at nucleotide 8721-8722. The second mutation is a single base insertion in exon 3 between nucleotides 2467 and 2468. The third mutation is a missense error present in the eighth exon of the C1INH; at nucleotide 16867 (amino acid 470), a T to A mutation transforms a Met to a Lys. The fourth mutation closely resembles the third mutation in that it is a missense error occurring in exon 8 in the distal hinge region; a T16827C substitution changes the Phe at amino acid 457 to Leu. This report compiles a list of 97 distinct defects in the C1INH gene that cause hereditary angioedema.

Transcriptomic analysis of growth heterosis in larval Pacific oysters (Crassostrea gigas)

Compared with understanding of biological shape and form, knowledge is sparse regarding what regulates growth and body size of a species. For example, the genetic and physiological causes of heterosis (hybrid vigor) have remained elusive for nearly a century. Here, we investigate gene-expression patterns underlying growth heterosis in the Pacific oyster (Crassostrea gigas) in two partially inbred (f = 0.375) and two hybrid larval populations produced by a reciprocal cross between the two inbred families. We cloned cDNA and generated 4.5 M sequence tags with massively parallel signature sequencing. The sequences contain 23,274 distinct signatures that are expressed at statistically nonzero levels and show a highly positively skewed distribution with median and modal counts of 9.25 million and 3 transcripts per million, respectively. For nearly half of these signatures, expression level depends on genotype and is predominantly nonadditive (hybrids deviate from the inbred average). Statistical contrasts suggest approximately 350 candidate genes for growth heterosis that exhibit concordant nonadditive expression in reciprocal hybrids; this represents only approximately 1.5% of the >20,000 transcripts. Patterns of gene expression, which include dominance for low expression and even underdominance of expression, are more complex than predicted from classical dominant or overdominant explanations of heterosis. Preliminary identification of ribosomal proteins among candidate genes supports the suggestion from previous studies that efficiency of protein metabolism plays a role in growth heterosis.

Functional analysis of maize RAD51 in meiosis and double-strand break repair

In Saccharomyces cerevisiae, Rad51p plays a central role in homologous recombination and the repair of double-strand breaks (DSBs). Double mutants of the two Zea mays L. (maize) rad51 homologs are viable and develop well under normal conditions, but are male sterile and have substantially reduced seed set. Light microscopic analyses of male meiosis in these plants reveal reduced homologous pairing, synapsis of nonhomologous chromosomes, reduced bivalents at diakinesis, numerous chromosome breaks at anaphase I, and that >33% of quartets carry cells that either lack an organized nucleolus or have two nucleoli. This indicates that RAD51 is required for efficient chromosome pairing and its absence results in nonhomologous pairing and synapsis. These phenotypes differ from those of an Arabidopsis rad51 mutant that exhibits completely disrupted chromosome pairing and synapsis during meiosis. Unexpectedly, surviving female gametes produced by maize rad51 double mutants are euploid and exhibit near-normal rates of meiotic crossovers. The finding that maize rad51 double mutant embryos are extremely susceptible to radiation-induced DSBs demonstrates a conserved role for RAD51 in the repair of mitotic DSBs in plants, vertebrates, and yeast.

Gastrointestinal teratomas: CT and US appearance with pathologic correlation

Gastrointestinal teratomas are uncommon, benign neoplasms that occur primarily in children. A retrospective review of five cases (two gastric, one pancreatic, one mesenteric, and one in the lesser omentum) is presented with emphasis on the computed tomographic and ultrasonographic appearances. Principal findings are a well-defined mass with separate cystic and solid components of varying proportions, discrete areas with densities similar to that of fat, or coarse, globular calcifications within the solid component. Recognition of these findings may allow the radiologist to make a correct preoperative diagnosis of teratoma.

A randomized trial measuring fecal blood loss after treatment with rofecoxib, ibuprofen, or placebo in healthy subjects

PURPOSE

Gastrointestinal microbleeding, as assessed by the measurement of (51)chromium-labeled red blood cells, is a marker of the mucosal injury associated with the use of nonsteroidal anti-inflammatory drugs. This study tested the hypotheses that cyclooxygenase-2 specific inhibition with rofecoxib would cause less fecal blood loss than a therapeutic dose of ibuprofen and would be equivalent to placebo.

SUBJECTS AND METHODS

In this randomized, double-blind group study, gastrointestinal blood loss was assessed by measurement of fecal (51)chromium radioactivity during a 1-week placebo baseline period and during 4 weeks of treatment with rofecoxib (25 mg or 50 mg once daily), ibuprofen (800 mg three times daily), or placebo in 67 healthy subjects. Gastrointestinal blood loss during treatment weeks 2 to 4 (versus the baseline period) was expressed as the geometric mean ratio of fecal radioactivity in weeks 2 to 4 compared with baseline.

RESULTS

Ibuprofen caused significantly (P <0.001) greater gastrointestinal blood loss (geometric mean ratio of 5.2, 95% confidence interval [CI]: 4.2 to 6.3) than the 25-mg dose of rofecoxib (2.6, 95% CI: 2.2 to 3.1), the 50-mg dose of rofecoxib (2.6, 95% CI: 2.2 to 3.0), or placebo (2.1, 95% CI: 1.8 to 2.5). In contrast, gastrointestinal blood loss with both doses of rofecoxib were equivalent to placebo by a predetermined clinical similarity bound.

CONCLUSIONS

In healthy subjects, treatment with rofecoxib, at 2 to 4 times the doses that are currently recommended for the treatment of patients with osteoarthritis, produced significantly less fecal blood loss than a therapeutic dose of ibuprofen and was equivalent to placebo.

Human ATP synthase beta is phosphorylated at multiple sites and shows abnormal phosphorylation at specific sites in insulin-resistant muscle

AIMS/HYPOTHESIS

Insulin resistance in skeletal muscle is linked to mitochondrial dysfunction in obesity and type 2 diabetes. Emerging evidence indicates that reversible phosphorylation regulates oxidative phosphorylation (OxPhos) proteins. The aim of this study was to identify and quantify site-specific phosphorylation of the catalytic beta subunit of ATP synthase (ATPsyn-beta) and determine protein abundance of ATPsyn-beta and other OxPhos components in skeletal muscle from healthy and insulin-resistant individuals.

METHODS

Skeletal muscle biopsies were obtained from lean, healthy, obese, non-diabetic and type 2 diabetic volunteers (each group n = 10) for immunoblotting of proteins, and hypothesis-driven identification and quantification of phosphorylation sites on ATPsyn-beta using targeted nanospray tandem mass spectrometry. Volunteers were metabolically characterised by euglycaemic-hyperinsulinaemic clamps.

RESULTS

Seven phosphorylation sites were identified on ATPsyn-beta purified from human skeletal muscle. Obese individuals with and without type 2 diabetes were characterised by impaired insulin-stimulated glucose disposal rates, and showed a approximately 30% higher phosphorylation of ATPsyn-beta at Tyr361 and Thr213 (within the nucleotide-binding region of ATP synthase) as well as a coordinated downregulation of ATPsyn-beta protein and other OxPhos components. Insulin increased Tyr361 phosphorylation of ATPsyn-beta by approximately 50% in lean and healthy, but not insulin-resistant, individuals.

CONCLUSIONS/INTERPRETATION

These data demonstrate that ATPsyn-beta is phosphorylated at multiple sites in human skeletal muscle, and suggest that abnormal site-specific phosphorylation of ATPsyn-beta together with reduced content of OxPhos proteins contributes to mitochondrial dysfunction in insulin resistance. Further characterisation of phosphorylation of ATPsyn-beta may offer novel targets of treatment in human diseases with mitochondrial dysfunction, such as diabetes.

Sensitivity and specificity of positron emission tomography and magnetic resonance imaging studies in Alzheimer's disease and multi-infarct dementia

Positron emission tomographic (PET) scans using [18F]-fluorodeoxyglucose and magnetic resonance imaging (MRI) scans were quantitatively analyzed for metabolic and structural abnormalities in normal subjects and patients classified as having Alzheimer's disease (AD), mixed dementia and multi-infarct dementia (MID) according to Hachinski ischemic scores. MRI-detected abnormalities in the periventricular white matter and in subcortical locations increased in incidence with age in normals and increased markedly in AD and especially in MID. Upper limits for the severity of these white matter lesions could be defined only for normal young and elderly subjects, but not for AD, mixed or MID patients. PET scan abnormalities occurred in about 90% of demented patients and in 54% of elderly and 34% of young normals. There was no characteristic pattern of abnormality that distinguished MID from AD patients. It is concluded that PET and MRI studies in demented patients are useful ancillary tests especially in evaluating the mild, questionably demented subject and for assessing the functional impact of structural disease.

Localization of an acetylcholine receptor intron to the nuclear membrane

The first intron of the RNA for the acetylcholine receptor (AChR) alpha subunit shows a ringlike distribution around nuclei in multinucleated myotubes by in situ hybridization. This pattern is not observed for an actin intron or U1 RNA. Quantitation of the intron sequences reveals large variations in the amount of both the AChR and actin introns between nuclei within the same myotube, although all nuclei express equivalent amounts of U1 RNA. This differential RNA expression indicates that nuclei can individually control expression of messenger RNAs. The restricted distribution of the AChR intron RNA suggests a previously unknown step in RNA processing.

Complex structure of a maize Myb gene promoter: functional analysis in transgenic plants

The maize P gene encodes a Myb-like transcription factor that regulates synthesis of red flavonoid pigments in floral organs. To study the transcriptional regulation of the P gene, candidate regulatory sequences of the P1-rr gene promoter were identified by Ac insertional mutagenesis and subjected to functional testing in transgenic maize plants. The results indicate that a 561 bp fragment (Pb) encompassing the transcription start site (-235 to +326) supports weak expression of a GUS reporter gene in floral organs, including husk, silk, kernel pericarp, cob and male inflorescence. Two other fragments, located approximately 1 and 5 kb 5' of the transcription start site, increased the levels of GUS activity in floral tissues and thus appear to contain enhancer elements. All of the tested constructs gave similar patterns of GUS expression, suggesting that the 561 bp Pb fragment that is common among the transgene constructs contains regulatory elements that promote activation in floral organs. The basal promoter and proximal enhancer fragments contain putative binding sites for bZip regulatory factors, and a complex arrangement of palindromes including a large inverted repeat of two tRNA-like genes. Possibly, interconversions between linear and cruciform conformations of the palindromes may affect protein/DNA interactions and thereby modulate P1-rr expression.

Conserved features of cancer cells define their sensitivity to HAMLET-induced death; c-Myc and glycolysis

HAMLET is the first member of a new family of tumoricidal protein-lipid complexes that kill cancer cells broadly, while sparing healthy, differentiated cells. Many and diverse tumor cell types are sensitive to the lethal effect, suggesting that HAMLET identifies and activates conserved death pathways in cancer cells. Here, we investigated the molecular basis for the difference in sensitivity between cancer cells and healthy cells. Using a combination of small-hairpin RNA (shRNA) inhibition, proteomic and metabolomic technology, we identified the c-Myc oncogene as one essential determinant of HAMLET sensitivity. Increased c-Myc expression levels promoted sensitivity to HAMLET and shRNA knockdown of c-Myc suppressed the lethal response, suggesting that oncogenic transformation with c-Myc creates a HAMLET-sensitive phenotype. Furthermore, HAMLET sensitivity was modified by the glycolytic state of tumor cells. Glucose deprivation sensitized tumor cells to HAMLET-induced cell death and in the shRNA screen, hexokinase 1 (HK1), 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 1 and hypoxia-inducible factor 1α modified HAMLET sensitivity. HK1 was shown to bind HAMLET in a protein array containing ∼8000 targets, and HK activity decreased within 15 min of HAMLET treatment, before morphological signs of tumor cell death. In parallel, HAMLET triggered rapid metabolic paralysis in carcinoma cells. Tumor cells were also shown to contain large amounts of oleic acid and its derivatives already after 15 min. The results identify HAMLET as a novel anti-cancer agent that kills tumor cells by exploiting unifying features of cancer cells such as oncogene addiction or the Warburg effect.