ETS family of genes in leukemia and Down syndrome

The human ETS2 and ERG genes are members of the ETS gene family, with sequence homology to the viral ets gene of the avian erythroblastosis retrovirus, E26. These genes are located on chromosome 21 and molecular genetic analysis of Down syndrome (DS) patients with partial trisomy 21 suggested that ETS2 may be a gene within the minimal DS genetic region. We have, in fact, been able to confirm the presence of the ETS2 gene dosage in triplicate occurring in occult human 21 chromosome abnormalities. It is known that ERG and ETS2 gene translocations occur in certain specific leukemias associated with defined chromosome rearrangements [e.g., t(8;21)]. Moreover, it is known that DS individuals are at greater risk for leukemic disease than their normal familial cohorts, implying that trisomy of that region of human chromosome 21 may play a role in the development of this type of neoplasia. The human ETS genes, first identified in our laboratory, are highly conserved, being found from lower organisms, like Drosophila and sea urchin, to humans. In mammals, the ETS genes are structurally distinct, located on separate chromosomes; they are transcriptionally active and differentially regulated. The ETS2 protein is phosphorylated and turns over with a half-life of approximately 20 min. After activation with the tumor promoter, TPA, the level of ETS2 elevates 5- to 20-fold. The properties of the ETS2 protein, such as nuclear localization, phosphorylation, rapid turnover, and response to protein kinase C, indicate that this protein belongs to a group of oncogene proteins thought to have regulatory functions in the nucleus. In the mouse thymus ets-1 and ets-2 are 8-10-fold higher, respectively, in the CD4+ subset than in other subsets examined, suggesting a role in T-cell development for these genes. Cells transfected with the cellular ets-2 gene, expressing higher levels of ets-2 products, showed a stimulated proliferation response, abolished their serum requirement and formed colonies in soft agar that could induce tumors in nude mice. Collectively, these data suggest that this family of genes might play a role in controlling specific steps of the signaling transduction pathway. Thus, the ETS genes, as other genes with homology to viral oncogenes, might be instrumental in regulating cellular growth and differentiation, as well as organismal development.

Examination of Phosphoryl-Mimicking Functionalities within a Macrocyclic Grb2 SH2 Domain-Binding Platform

Reported herein are the design, synthesis, and Grb2 SH2 domain-binding affinities of several phosphoryl-mimicking groups displayed within the context of a conformationally constrained macrocyclic platform. With use of surface plasmon resonance techniques, single-digit nanomolar affinities were exhibited by phosphonic acid and malonyl-containing diacidic phosphoryl mimetics (for 4h and 4g, K(D) = 1.47 and 3.62 nM, respectively). Analogues containing monoacidic phosphoryl mimetics provided affinities of K(D) = 16-67 nM. Neutral phosphoryl-mimicking groups did not show appreciable binding.

Utilization of a Common Pathway for the Synthesis of High Affinity Macrocyclic Grb2 SH2 Domain-Binding Peptide Mimetics That Differ in the Configuration at One Ring Junction

As typified by 2-{(9S,10S,14R,18S)-18-(2-amino-2-oxoethyl)-14-[(5-methyl-1H-indol-1-yl)methyl]-8,17,20-trioxo-10-[4-(phosphonomethyl)phenyl]-7,16,19-triazaspiro[5.14]icos-11-en-9-yl}acetic acid ((14R)-1b), ring-closing methathesis-derived macrocyclic tetrapeptide mimetics have recently been reported that bind with high affinity to Grb2 SH2 domains in both extracellular and whole-cell assays. The synthetic complexity of this class of agents limits further therapeutic development. Although a significant component of this synthetic complexity arises from the presence of three stereogenic centers, C(9) (S), C(10) (S), and C(14) (R), it is unclear whether stereoselective introduction of defined configuration at C(14) is required for high-affinity binding. Reported herein is a synthetic route to these macrocycles lacking stereoselectivity in the formation of the C(14) ring junction, which is four synthetic steps shorter than the original stereoselective synthesis. Separation of C(14)-epimers obtained by this approach was achieved by preparative HPLC. Molecular-dynamics studies of ligands bound to the Grb2 SH2 domain protein indicated that the (14R)-configuration should display more-favorable interactions with the protein relative to the (14S)-epimer. Indeed, although surface-plasmon-resonance-derived binding constants to Grb2 SH2 domain protein indicated that the affinity of the (14R)-epimer (KD = 4.8 nM) is greater than that of the (14S)-epimer (KD = 11 nM), it is only marginally so. Therefore, little affinity would be lost through a non-stereoselective synthesis of the C(14)-center. Further studies are in progress to explore reduced structural complexity at the C(14)-center.

Design and synthesis of conformationally constrained Grb2 SH2 domain binding peptides employing alpha-methylphenylalanyl based phosphotyrosyl mimetics

Previous work has shown that incorporation of either 1-aminocyclohexanecarboxylic acid (Ac6c) or alpha-methyl-p-phosphonophenylalanine ((alpha-Me)Ppp) in the phosphotyrosyl (pTyr) C-proximal position (pY + 1 residue) of Grb2 SH2 domain binding peptides confers high affinity. The tetralin-based (S)-2-amino-6-phosphonotetralin-2-carboxylic acid (Atc(6-PO3H2)) simultaneously presents structural features of both (alpha-Me)Ppp and Ac6c residues. The current study compares the affinity of this tetralin hybrid Atc(6-PO3H2) versus Ac6c and (alpha-Me)Ppp residues when incorporated into the pY + 1 position of a high-affinity Grb2 SH2 domain binding tripeptide platform. The highest binding affinity (KD = 14.8 nM) was exhibited by the (alpha-Me)Ppp-containing parent, with the corresponding Ac6c-containing peptide being nearly 2-fold less potent (KD = 23.8 nM). The lower KD value was attributable primarily to a 50% increase in off-rate. Replacement of the Ac6c residue with the tetralin-based hybrid resulted in a further 4-fold decrease in binding affinity (KD = 97.8 nM), which was the result of a further 6-fold increase in off-rate, offset by an approximate 45% increase in on-rate. Therefore, by incorporation of the key structural components found in (alpha-Me)Ppp into the Ac6c residue, the tetralin hybrid does enhance binding on-rate. However, net binding affinity is decreased due to an associated increase in binding off-rate. Alternatively, global conformational constraint of an (alpha-Me)Ppp-containing peptide by beta-macrocyclization did result in pronounced elevation of binding affinity, which was achieved primarily through a decrease in the binding off-rate. Mathematical fitting using a simple model that assumed a single binding site yielded an effective KD of 2.28 nM. However this did not closely approximate the data obtained. Rather, use of a complex model that assumed two binding sites resulted in a very close fit of data and provided KD values of 97 pM and 72 nM for the separate sites, respectively. Therefore, although local conformational constraint in the pY + 1 residue proved to be deleterious, global conformational constraint through beta-macrocyclization achieved higher affinity. Similar beta-macrocyclization may potentially be extended to SH2 domain systems other than Grb2, where bend geometries are required.

Ring-Closing Metathesis of C-Terminal Allylglycine Residues with an N-Terminal β-Vinyl-Substituted Phosphotyrosyl Mimetic as an Approach to Novel Grb2 SH2 Domain-Binding Macrocycles

Ring-closing metathesis (RCM) of peptides often requires insertion of allylglycines at the intended sites of ring juncture, which can result in the displacement of residues that are needed for biological activity. This type of side-chain deletion can be avoided by appending beta-vinyl substituents onto the parent residues at the intended sites of ring juncture, thereby effectively converting them into functionalized allylglycine equivalents. Such an approach has been previously applied in modified form to growth-factor receptor bound 2 (Grb2) SH2 domain-binding peptides by using an N-terminal beta-vinyl-functionalized phosphotyrosyl mimetic and C-terminal 2-allyl-3-aryl-1-propanamides that lacked the alpha-carboxyl portion of allylglycine residues. These C-terminal moieties involved lengthy synthesis and once prepared, required an individual total synthesis of each final macrocycle. Work reported herein significantly enhances the versatility of the original approach through the use of C-terminal allylglycine amides that can be prepared from commercially available L- and D-allylglycines and suitable amines. This methodology could be generally useful where macrocylization is desired with maintenance of functionality at a site of ring juncture.

Organic solvent extraction of proteins and peptides from serum as an effective sample preparation for detection and identification of biomarkers by mass spectrometry

A method to extract peptides and low molecular weight proteins from serum under denaturing conditions using acetonitrile containing 0.1% trifluoroacetic acid has been developed. The extraction procedure precipitates large, abundant proteins to simplify subsequent mass spectral analysis. This sample preparation method provides an efficient way to extract serum peptides, enabling them to be compared and identified using different mass spectrometry approaches. Surface-enhanced laser desorption/ionization-time of flight mass spectrometry analysis of mouse blood serum samples prepared by this method allowed detection of two markers which were significantly reduced in mice with B cell lymphoma tumor. One of these markers has been identified as apolipoprotein A-II.

Stimulation of in vivo angiogenesis by cytokine-loaded hyaluronic acid hydrogel implants

Crosslinked hyaluronic acid (HA) hydrogels were evaluated for their ability to elicit new microvessel growth in vivo when preloaded with one of two cytokines, vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF). HA film samples were surgically implanted in the ear pinnas of mice, and the ears retrieved 7 or 14 days post implantation. Histologic analysis showed that all groups receiving an implant demonstrated significantly more microvessel density than control ears undergoing surgery but receiving no implant (p < 0.01). Moreover, aqueous administration of either growth factor produced substantially more vessel growth than an HA implant with no cytokine. However, the most striking result obtained was a dramatic synergistic interaction between HA and VEGF. Presentation of VEGF in crosslinked HA generated vessel density of NI = 6.7 at day 14, where NI is a neovascularization index defined below, more than twice the effect of the sum of HA alone (NI = 1.8) plus VEGF alone (NI=1.3). This was twice the vessel density generated by co-addition of HA and bFGF (NI=3.4, p<0.001). New therapeutic approaches for numerous pathologies could be notably enhanced by the localized, synergistic angiogenic response produced by release of VEGF from crosslinked HA films.

Coupling of Oscillatory Activity Between Muscles Is Strikingly Reduced in a Deafferented Subject Compared With Normal Controls

Oscillatory activity in the primate motor cortex has been shown to be phase locked to oscillations in contralateral hand and forearm muscle activity in the 15- to 30-Hz frequency range. Recent studies have shown that the degree of coupling between the cortex and the periphery is strongly influenced by the type and degree of movements of the digits. It has also been suggested that changes in corticomuscular and muscle-muscle coherence could be modulated by peripheral sensory inputs. In the current study, we investigated task-dependent changes in the coherent coupling of electromyographic (EMG) activity recorded from different intrinsic (abductor pollicis brevis and first dorsal interosseous) and two extrinsic (flexor digitorum superficialis and extensor digitorum communis) hand muscles during performance of a precision-grip task by normal subjects and by a single subject who has a total loss of touch, vibration, pressure, and kinesthetic sensation below the neck. The task required a hold-move-hold pattern of grip force to be exerted on a compliant object with the dominant right hand. We found significant task-related modulation of 15- to 30-Hz coherence between EMG activity in hand muscles in the control subjects. In contrast, the deafferented subject showed very low levels of significant coherence in the 15- to 30-Hz range and no peak at this frequency in the power spectra of her EMG activity. These results suggest that the presence of sensory afferent signals are necessary for the modulation of 15- to 30-Hz oscillations in the motor system.

Effects of combined cortical and acoustic stimuli on muscle activity

Hitherto, it has proven difficult to investigate interactions between cerebral and brainstem motor systems in the human. We hypothesised that transcranial magnetic stimulation (TMS) centred over the dorsal premotor and primary motor cortices might elicit net facilitatory cortico-reticular effects that could interact at the level of the brainstem with a habituated startle to give a reticulospinal discharge and electromyographic (EMG) response with a longer latency than the direct corticospinal response. Conversely, any reticulo-cortical activity evoked by a habituated startle should influence the size of the direct response to cortical TMS. EMG was recorded from active left deltoid muscle in nine healthy volunteers. Acoustic stimulation was delivered binaurally through headphones and repeated until the startle response was habituated. When TMS was centred over the right dorsal premotor or primary motor cortices and delivered 50 ms after the habituated acoustic stimulus, the contralateral direct motor evoked potential was inhibited, compared with the response elicited by TMS alone. The contralateral silent period was shortened and associated with less of a decrease in EMG levels relative to TMS alone. Indeed, an actual increase in EMG over baseline levels occurred in the later half of the silent period in all subjects. We conclude that both cortico-reticular and reticular-cortical effects could be elicited in deltoid through the combination of acoustic stimulation and TMS at short interstimulus intervals. Effects were similar with TMS over premotor and primary motor cortex.

Comparative analyses of a small molecule/enzyme interaction by multiple users of Biacore technology

To gauge the experimental variability associated with Biacore analysis, 36 different investigators analyzed a small molecule/enzyme interaction under similar conditions. Acetazolamide (222 g/mol) binding to carbonic anhydrase II (CAII; 30000 Da) was chosen as a model system. Both reagents were stable and their interaction posed a challenge to measure because of the low molecular weight of the analyte and the fast association rate constant. Each investigator created three different density surfaces of CAII and analyzed an identical dilution series of acetazolamide (ranging from 4.1 to 1000 nM). The greatest variability in the results was observed during the enzyme immobilization step since each investigator provided their own surface activating reagents. Variability in the quality of the acetazolamide binding responses was likely a product of how well the investigators' instruments had been maintained. To determine the reaction kinetics, the responses from the different density surfaces were fit globally to a 1:1 interaction model that included a term for mass transport. The averaged association and dissociation rate constants were 3.1+/-1.6 x 10(6)M(-1)s(-1) and 6.7+/-2.5 x 10(-2)s(-1), respectively, which corresponded to an average equilibrium dissociation constant (K(D) of 2.6+/-1.4 x 10(-8)M. The results provide a benchmark of variability in interpreting binding constants from the biosensor and highlight keys areas that should be considered when analyzing small molecule interactions.

Synthesis of a 5-methylindolyl-containing macrocycle that displays ultrapotent Grb2 SH2 domain-binding affinity

The growth factor receptor-bound protein 2 (Grb2) is an SH2 domain-containing docking module that represents an attractive target for anticancer therapeutic intervention. Here, a ring-closing metathesis approach is utilized to synthesize a 5-methylindolyl-containing tetrapeptide mimetic (6) that exhibits unprecedented in vitro Grb2 SH2 domain-binding affinity (K(d) = 93 pM). Key to the preparation of 6 is the enantioselective synthesis of (2S)-2-(3-(5-methylindolyl)methyl)pent-4-enylamine (12) as one of two ring-closing segments.

Macrocyclization in the Design of Non-Phosphorus-Containing Grb2 SH2 Domain-Binding Ligands

Macrocyclization from the phosphotyrosyl (pTyr) mimetic's beta-position has previously been shown to enhance Grb2 SH2 domain-binding affinity of phosphonate-based analogues. The current study examined the effects of such macrocyclization using a dicarboxymethyl-based pTyr mimetic. In extracellular assays affinity was enhanced approximately 5-fold relative to an open-chain congener. Enhancement was also observed in whole-cell assays examining blockade of Grb2 binding to the erbB-2 protein-tyrosine kinase.

The Octapeptidic End of the C-Terminal Tail of Histone H2A Is Cleaved Off in Cells Exposed to Carcinogenic Nickel(II)

We have demonstrated previously that Ni(II) binds to the C-terminal -TESHHKAKGK motif of isolated bovine histone H2A. At physiological pH, the bound Ni(II) assists in hydrolysis of the E-S peptide bond in this motif that results in a cleavage of the terminal octapeptide SHHKAKGK off the histone's C-tail. To test if the hydrolysis could also occur in living cells, we cultured CHO (Chinese hamster ovary), NRK-52 (rat renal tubular epithelium), and HPL1D (human lung epithelium) cells with 0.1-1 mM Ni(II) for 3-7 days. As found by gel electrophoresis, Western blotting, and liquid chromatography/mass spectrometry, histones extracted from the cells contained a new fraction of histone H2A lacking the terminal octapeptide (q-H2A). The abundance of q-H2A increased with Ni(II) concentration and exposure time. It can be anticipated that the truncation of histone H2A may alter chromatin structure and affect gene expression. The present results provide evidence for novel mechanisms of epigenetic effects of Ni(II) that may be involved in nickel toxicity and carcinogenesis.

A novel macrocyclic tetrapeptide mimetic that exhibits low-picomolar Grb2 SH2 domain-binding affinity

The growth factor receptor-bound protein 2 (Grb2) is an SH2 domain-containing docking module that participates in the signaling of numerous oncogenic growth factor receptor protein-tyrosine kinases (PTKs). Presented herein is a 5-methylindolyl-containing macrocyclic tetrapeptide mimetic (5) that binds to Grb2 SH2 domain protein with K(d)=75 pM. This represents the highest affinity yet reported for a synthetic inhibitor against any SH2 domain. In whole cell assays this novel analogue is able to effectively block the association of Grb2 to cognate cytoplasmic erbB-2 at IC(50)<10nM without prodrug derivatization or the addition of carrier peptide motifs. Anti-mitogenic effects against erbB-2-dependent breast cancers are achieved at non-cytotoxic concentrations (IC(50)=0.6 microM). Macrocycle 5 may be representative of a new class of therapeutically relevant Grb2 SH2 domain-directed agents.

A high-throughput screen for identification of molecular mimics of Smac/DIABLO utilizing a fluorescence polarization assay

Resistance to apoptosis is afforded by inhibitor of apoptosis proteins (IAPs) which bind to and inhibit the caspases responsible for cleavage of substrates leading to apoptotic cell death. Smac (or DIABLO), a proapoptotic protein released from the mitochondrial intermembrane space into the cytosol, promotes apoptosis by binding to IAPs, thus reversing their inhibitory effects on caspases. We have developed a high-throughput fluorescence polarization assay utilizing a fluorescein-labeled peptide similar to the "IAP binding" domain of Smac N terminus complexed with the BIR3 domain of X-linked IAP (XIAP) to identify small-molecule mimics of the action of Smac. The IC(50)s of peptides and a tetrapeptidomimetic homologous to the N terminus of Smac demonstrated the specificity and utility of this assay. We have screened the National Cancer Institute "Training Set" of 230 compounds, with well-defined biological actions, and the "Diversity Set" of 2000 chemically diverse structures for compounds which significantly reduced fluorescence polarization. Highly fluorescing or fluorescence-quenching compounds (false positives) were distinguished from those which interfered with Smac peptide binding to the XIAP-BIR3 in a dose-dependent manner (true positives). This robust assay offers potential for high-throughput screening discovery of novel compounds simulating the action of Smac/DIABLO.

Quantitative proteomics employing primary amine affinity tags

A proteomics-based method using stable isotope labeling to assess the relative abundance of peptides or proteins is described. Bradykinin and carbonic anhydrase were labeled with sulfosuccinimidyl-2-(biotinamido) ethyl-1,3-dithiopropionate, a membrane impermeant reagent that is reactive with primary amines. Specificity of the label to primary amines was demonstrated using tandem mass spectrometry. Also, relative quantitation was achieved by secondary labeling with natural isotopic abundance and stable isotope-labeled methyl iodide. We believe this to be an effective stable isotope-labeling method for quantitative proteomics.

A novel mechanism for inhibition of HIV-1 reverse transcriptase

The human immunodeficiency virus (HIV) epidemic is an important medical problem. Although combination drug regimens have produced dramatic decreases in viral load, current therapies do not provide a cure for HIV infection. We have used structure-based design and combinatorial medicinal chemistry to identify potent and selective HIV-1 reverse transcriptase (RT) inhibitors that may work by a mechanism distinct from that of current HIV drugs. The most potent of these compounds (compound 4, 2-naphthalenesulfonic acid, 4-hydroxy-7-[[[[5-hydroxy-6-[(4-cinnamylphenyl)azo]-7-sulfo-2-naphthalenyl]amino]carbonyl]amino]-3-[(4-cinnamylphenyl)azo], disodium salt) has an IC(50) of 90 nM for inhibition of polymerase chain extension, a K(d) of 40 nM for inhibition of DNA-RT binding, and an IC(50) of 25-100 nM for inhibition of RNaseH cleavage. The parent compound (1) was as effective against 10 nucleoside and non-nucleoside resistant HIV-1 RT mutants as it was against the wild-type enzyme. Compound 4 inhibited HIV-1 RT and murine leukemia virus (MLV) RT, but it did not inhibit T(4) DNA polymerase, T(7) DNA polymerase, or the Klenow fragment at concentrations up to 200 nM. Finally, compound 4 protected cells from HIV-1 infection at a concentration more than 40 times lower than the concentration at which it caused cellular toxicity.

The identification of thymidylate synthase peptide domains located in the interface region that bind thymidylate synthase mRNA

Thymidylate synthase (TS) is a critical chemotherapeutic target and intracellular levels of TS are an important determinant of sensitivity to TS inhibitors. Translational autoregulation represents one cellular mechanism for controlling the level of expression of TS. This mechanism involves the binding of TS protein to its own messenger RNA (mRNA), thus, repressing translational efficiency. The presence of excess substrate or inhibitors of TS leads to derepression of protein binding to mRNA, resulting in increased translational efficiency and ultimately increased levels of TS protein. TS protein has been shown to bind to two distinct areas on its mRNA. The goal of the present work is to define the TS domains responsible for this interaction. Using a separate series of overlapping 17-mer peptides spanning the length of both the human and Escherichia coli TS sequences, we have identified six potential domains located in the interface region of the TS protein that bind TS mRNA. The identified domains that bind TS mRNA include three concordant regions in both the human and E. coli peptide series. Five of the six binding peptides contain at least one invariant arginine residue, which has been shown to be critical in other well-defined protein-RNA interactions. These data suggest that the identified highly conserved protein domains, which occur at the homodimeric interface of TS, represent potential participating sites for binding of TS protein to its mRNA.

Identification of HIV-1 nucleocapsid protein: nucleic acid antagonists with cellular anti-HIV activity

The crucial functions of HIV-1 nucleocapsid-p7 protein (NC-p7) at different stages of HIV replication are dependent on its nucleic acid binding properties. In this study, a search has been made to identify antagonists of the interaction between NC-p7 and d(TG)(4). A chemical library of approximately 2000 small molecules (the NCI Diversity Set) was screened, of the 26 active inhibitors that were identified, five contained a xanthenyl ring structure. Further analysis of 63 structurally related compounds led to the identification of 2,3,4,5-tetrachloro-6-(4('),5('),6(')-trihydroxy-3(')-oxo-3H-xanthen-9(')-yl)benzoic acid, which binds to NC-p7 stoichiometrically. This compound exerted a significant anti-HIV activity in vitro with an IC(50) of 16.6+/-4.3 microM (means+/-SD). Synthetic variants lacking the two hydroxyls at positions 4(') and 5(') in the xanthenyl ring system failed to bind NC-p7 and showed significantly less protection against HIV infection. Molecular modeling predicts that these hydroxyl groups would bind to the amide nitrogen of Gly(35) with other contacts at the carbonyl oxygens of Gly(40) and Lys(33).

Digital nerve anaesthesia decreases EMG-EMG coherence in a human precision grip task

There is increasing evidence that the primary motor cortex is involved in the generation of electromyographic (EMG) oscillations at frequencies in the range of 15-30 Hz that are observed during performance of a precision grip task. Since the level of the corticomuscular coherence varies according to the nature of the object that is gripped, it seemed possible that somatosensory inputs from the hand might affect this coherence. The aim of this study was to investigate whether interrupting cutaneous inputs from the digits would affect the coherence between hand muscles during precision grip of a compliant object. Subjects performed a precision grip hold-ramp-hold task before, during and after digital nerve anaesthesia of the index finger and thumb. There were marked deficits in the performance of the task, particularly during the initial formation of the grip and first hold period. Local digital nerve anaesthesia reduced but did not abolish 14-31 Hz coherence between EMG activity recorded from different hand and forearm muscles. Coherence was measured during the second hold phase of the task. Digital nerve anaesthesia did not affect the predominant frequencies in the EMG power spectra compiled from the same phase of the task. We conclude that during a precision grip task, cutaneous input enhances oscillatory synchrony between pairs of hand muscles.

Two phases of intracortical inhibition revealed by transcranial magnetic threshold tracking

Intracortical inhibition was investigated in normal human volunteers by paired-pulse transcranial magnetic stimulation, using a new, computer-assisted threshold-tracking method. Motor threshold was defined as the stimulus amplitude required to evoke a motor evoked potential of 0.2 mV (peak-to-peak) in abductor pollicis brevis, and inhibition was measured as the percentage increase in threshold, when the test stimulus was preceded by a subthreshold conditioning stimulus. This method was used to investigate the dependence of intracortical inhibition on conditioning stimulus parameters and on voluntary activity. Interstimulus interval (ISI) was first stepped from 1 to 4.5 ms, as inhibition was measured using conditioning stimuli of fixed amplitude (50-90% resting motor threshold). Maximal inhibition was produced at ISIs of 1 and 2.5 ms. The effect of conditioning stimulus intensity was then assessed at these ISIs. Inhibition occurred at significantly lower conditioning stimulus intensities with ISI=1 ms than with ISI=2.5 ms. Voluntary activity reduced inhibition at both ISIs, but had a much greater effect on inhibition at ISI=2.5 ms. Inhibition during voluntary activity was also examined for single motor units in first dorsal interosseous by generating poststimulus time histograms. Inhibition, indicated by a reduction in the later peaks of increased firing, was observed with ISI=1 ms, but not with ISI=2.5 ms. We conclude that there are two distinct phases of inhibition, occurring at ISI=1 ms and ISI=2.5 ms, differing both in thresholds and susceptibility to voluntary activity.

Phosphorylation of the protein kinase C-theta activation loop and hydrophobic motif regulates its kinase activity, but only activation loop phosphorylation is critical to in vivo nuclear-factor-kappaB induction

Protein kinase C (PKC)-theta, a member of the 'novel' subfamily of PKC isoforms, is of singular importance in transducing signals in T-lymphocytes. Since understanding of regulatory phosphorylation of novel PKCs is fragmentary and inconsistent with findings for 'classical' PKC isoforms, we investigated three potential phosphorylation sites on PKC-theta; in the activation loop (Thr(538)), turn motif (Ser(676)) and hydrophobic motif (Ser(695)). Combined evidence from phospho-specific antisera and MS demonstrates phosphorylation at all three sites. Unlike its closest paralogue, PKC-delta, lack of negative charge in the activation loop of PKC-theta results in a profound catalytic defect (>100-fold reduction in the T538A mutant); the high sequence similarity between PKC-theta and -delta assists in the formulation of structural hypotheses to account for this major difference. In contrast with mechanisms proposed for other PKC isoforms, phosphorylation at the other two sites does not reconstitute catalytic activity. Activation loop phosphorylation is critical in vivo, since the T538A mutant completely lost its capacity to mediate T-cell receptor-stimulation of nuclear factor kappaB (NF-kappaB) activation in Jurkat T-cells. Hydrophobic motif phosphorylation also substantially influences PKC-theta catalytic activity (5-fold reduction in the S695A mutant), but does not impair NF-kappaB activation in Jurkat T-cells. Its mechanism is independent of secondary effects on activation loop phosphorylation and cannot be explained by thermal instability. Turn motif phosphorylation has a limited effect on kinase activity, but negatively regulates other aspects of PKC-theta function, since the S676A mutant is more efficient than wild-type in inducing NF-kappaB activation in Jurkat T-cells. These findings expand our understanding of the roles of phosphorylation in novel PKCs, and indicate that PKC-theta is a constitutively competent kinase as a consequence of constitutive phosphorylation of its activation loop.

Chemical cleavage at aspartyl residues for protein identification

An alternative method to enzymatic digestion for protein identification by mass spectrometry has been developed that is based on chemical cleavage by formic acid. This method was tested on gel-purified apomyoglobin and BSA, as well as unknown proteins that cofractionate with Tyl-virus-like particles from Saccharomyces cerevisiae. Cleavage at aspartyl residues was found to be efficient and specific, and this specificity of cleavage lent itself easily to database searches. Parallel digestions using trypsin were also performed. The formic acid cleavage method generated comparable or better results than tryptic digestion for protein identification.

Trophic factor withdrawal: p38 mitogen-activated protein kinase activates NHE1, which induces intracellular alkalinization

Trophic factor withdrawal induces cell death by mechanisms that are incompletely understood. Previously we reported that withdrawal of interleukin-7 (IL-7) or IL-3 produced a rapid intracellular alkalinization, disrupting mitochondrial metabolism and activating the death protein Bax. We now observe that this novel alkalinization pathway is mediated by the pH regulator NHE1, as shown by the requirement for sodium, blocking by pharmacological inhibitors or use of an NHE1-deficient cell line, and the altered phosphorylation of NHE1. Alkalinization also required the stress-activated p38 mitogen-activated protein kinase (MAPK). Inhibition of p38 MAPK activity with pharmacological inhibitors or expression of a dominant negative kinase prevented alkalinization. Activated p38 MAPK directly phosphorylated the C terminus of NHE1 within a 40-amino-acid region. Analysis by mass spectroscopy identified four phosphorylation sites on NHE1, Thr 717, Ser 722, Ser 725, and Ser 728. Thus, loss of trophic cytokine signaling induced the p38 MAPK pathway, which phosphorylated NHE1 at specific sites, inducing intracellular alkalinization.

Modulation of HIV-like particle assembly in vitro by inositol phosphates

HIV-1 Gag protein assembles into 100- to 120-nm diameter particles in mammalian cells. Recombinant HIV-1 Gag protein assembles in a fully defined system in vitro into particles that are only 25-30 nm in diameter and that differ significantly in other respects from authentic particles. However, particles with the size and other properties of authentic virions were obtained in vitro by addition of inositol phosphates or phosphatidylinsitol phosphates to the assembly system. Thus, the interactions between HIV-1 Gag protein molecules are altered by binding of inositol derivatives; this binding is apparently essential for normal HIV-1 particle assembly. This requirement is not seen in a deleted Gag protein lacking residues 16-99 within the matrix domain.

Control of membrane fusion dynamics during regulated exocytosis

The study of regulated exocytosis uniquely allows the direct measurement of intracellular membrane fusion events in real time. We have exploited this to examine factors that regulate not only the extent but also the dynamics of single fusion/release events. The general strategy used has been to assess exocytosis in transiently transfected PC12 or adrenal chromaffin cells. We aimed to design mutant constructs based on in vitro biochemistry, in some cases informed by knowledge of protein structure. Using this approach we have demonstrated an inhibitory role for the putative Rab3 effector Noc2 that requires interaction with Rab3. Using carbon-fibre amperometry on adrenal chromaffin cells, we have demonstrated regulation of the kinetics of single granule release events consistent with changes in fusion pore dynamics and switches between full fusion and 'kiss-and-run' fusion. These studies have demonstrated a late role for cysteine string protein in exocytosis. In addition, they have focused attention on a key role for Munc18 in the regulation of post-fusion events that affect fusion pore dynamics.

Neutralizing monoclonal antibodies to hepatocyte growth factor/scatter factor (HGF/SF) display antitumor activity in animal models

The hepatocyte growth factor (HGF/SF) receptor, Met, regulates mitogenesis, motility, and morphogenesis in a cell type-dependent fashion. Activation of Met via autocrine, paracrine, or mutational mechanisms can lead to tumorigenesis and metastasis and numerous studies have linked inappropriate expression of this ligand-receptor pair to most types of human solid tumors. To prepare mAbs to human HGF/SF, mice were immunized with native and denatured preparations of the ligand. Recloned mAbs were tested in vitro for blocking activity against scattering and branching morphogenesis. Our results show that no single mAb was capable of neutralizing the in vitro activity of HGF/SF, and that the ligand possesses a minimum of three epitopes that must be blocked to prevent Met tyrosine kinase activation. In vivo, the neutralizing mAb combination inhibited s.c. growth in athymic nu/nu mice of tumors dependent on an autocrine Met-HGF/SF loop. Importantly, growth of human glioblastoma multiforme xenografts expressing Met and HGF/SF were markedly reduced in the presence of HGF/SF-neutralizing mAbs. These results suggest interrupting autocrine and/or paracrine Met-HGF/SF signaling in tumors dependent on this pathway is a possible intervention strategy.

Control of fusion pore dynamics during exocytosis by Munc18

Intracellular membrane fusion is mediated by the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins. All vesicle transport steps also have an essential requirement for a member of the Sec1 protein family, including the neuronal Munc18-1 (also known as nSec1) in regulated exocytosis. Here, in adrenal chromaffin cells, we expressed a Munc18 mutant with reduced affinity for syntaxin, which specifically modified the kinetics of single-granule exocytotic release events, consistent with an acceleration of fusion pore expansion. Thus, Munc18 functions in a late stage in the fusion process, where its dissociation from syntaxin determines the kinetics of postfusion events.

Analysis of human immunodeficiency virus type 1 containing HERV-K protease

The human endogenous retrovirus, type K (HERV-K) represents the most biologically active form of known retroelements present in the human genome. Several HERV-K genomes have transcriptionally active open reading frames and encode their own protease (PR). The HERV-K PR has been shown to authentically cleave human immunodeficiency virus type 1 (HIV-1) matrix-capsid peptide in the presence of HIV-1 PR inhibitors. This raised the possibility that HERV-K PR could complement HIV-1 PR function in HIV-1-infected individuals. To investigate this possibility, we fused the HIV-1 vpr gene to the HERV-K PR gene (vpr-PR). The vpr-PR expression plasmid and a PR-defective HIV-1 clone were cotransfected into 293T cells. Progeny virions were assayed for processing of the HIV-1 polyproteins by Western blot and for changes in infectivity. HERV-K PR fused to Vpr was incorporated into HIV-1 virions at a high concentration and cleaved the Gag and Pol precursor proteins. However, neither Gag nor Pol polyproteins were correctly processed. Moreover, the HERV-K PR did not restore virus infectivity. While these results do not exclude the possibility that the HERV-K PR could complement an HIV-1 PR whose function is impaired due to drugs or drug-resistant mutations, they clearly demonstrate that the HERV-K PR cannot substitute for the function of the wild-type HIV-1 PR.

Measurement of exocytosis by amperometry in adrenal chromaffin cells: effects of clostridial neurotoxins and activation of protein kinase C on fusion pore kinetics

We have used carbon-fibre amperometry to examine the kinetics of individual secretory granule fusion/release events in bovine adrenal chromaffin cells. Transfection with plasmids encoding the light chains of botulinum neurotoxins (BoNTs) was used to investigate the effects of cleavage of syntaxin or SNAP-25 on exocytosis. Expression of BoNT/C1 or BoNT/E inhibited the extent of exocytosis that was evoked by application of digitonin/Ca(2+) to permeabilise and stimulate single chromaffin cells. Following neurotoxin expression, the residual release events were no different from those of control cells in their magnitude and kinetics from analysis of the amperometric spikes. In contrast, activation of protein kinase C (PKC) resulted in a modification of the kinetics of single granule release events. Following phorbol ester treatment, the amperometric spikes showed a significant decrease in their total charge due to a decrease in their mean half-width with increases in the rate of the initial rise and also the fall to baseline of the spikes. These changes were prevented by pre-treatment with the PKC inhibitor bisindolylmaleimide. These results suggest that PKC regulates the rate of fusion pore expansion and also subsequent pore closure or granule retrieval. A PKC-mediated regulation of kiss-and-run fusion may, therefore, control the extent of catecholamine release from single secretory granules. The experimental approach used here may provide further information on the protein constituents and regulation of the fusion pore machinery.

Genomic alterations (LOH, MI) on chromosome 17q21-23 and prognosis of sporadic colorectal cancer

Genomic alterations at the long arm of chromosome 17, and in particular at the nm23 locus, are still controversial in colorectal cancer (CRC). Our aim was to investigate the possible relationship of loss of heterozygosity (LOH) and microsatellite instability (MI), at 4 microsatellite loci spanning the 17q21-23 region, to the risk of liver metastasis and nm23 protein expression. Genomic DNA extracted from 58 primary and 54 liver secondary formalin-fixed and paraffin-embedded CRCs was obtained from 82 patients. A fluorescent PCR coupled with an automated DNA sequencer was applied. Increasing fraction of loci showing LOH was positively associated with risk of liver metastases (logrank test for trend, p = 0.005); this remained independent after adjusting to T-stage (Cox regression, p = 0.022), N-stage (p = 0.007), or Dukes' stage (p = 0.012). Conversely, increasing frequency of MI was associated with a reduced risk of liver metastases in Dukes' B tumours (logrank test for trend, p = 0.032). When comparing 30 primary and matched liver secondary lesions, we found concordant genomic alteration in 72% (NME1) to 43% (D17S579). Finally, we observed a trend in association between the proportion of loci with LOH and nm23 positivity (chi2 test for trend, p = 0.024). Our findings suggest that genomic alterations in the 17q21-23 region may affect prognosis of CRC as well as regulation of the nm23 protein expression via an unknown underlying mechanism.

A complete system for identifying inhibitors of creatine kinase B

We have developed a complete system for discovery of lead compounds as inhibitors of creatine kinase B. In this article, we describe production and purification of the recombinant protein, conditions and features of an optimized high-throughput screening assay, and results of our implementation of the system using a diverse compound library.

Genomic alterations (LOH, MI) on chromosome 17q21-23 and prognosis of sporadic colorectal cancer

Genomic alterations at the long arm of chromosome 17, and in particular at the nm23 locus, are still controversial in colorectal cancer (CRC). Our aim was to investigate the possible relationship of loss of heterozygosity (LOH) and microsatellite instability (MI), at 4 microsatellite loci spanning the 17q21-23 region, to the risk of liver metastasis and nm23 protein expression. Genomic DNA extracted from 58 primary and 54 liver secondary formalin-fixed and paraffin-embedded CRCs was obtained from 82 patients. A fluorescent PCR coupled with an automated DNA sequencer was applied. Increasing fraction of loci showing LOH was positively associated with risk of liver metastases (logrank test for trend, p = 0.005); this remained independent after adjusting to T-stage (Cox regression, p = 0.022), N-stage (p = 0.007), or Dukes' stage (p = 0.012). Conversely, increasing frequency of MI was associated with a reduced risk of liver metastases in Dukes' B tumours (logrank test for trend, p = 0.032). When comparing 30 primary and matched liver secondary lesions, we found concordant genomic alteration in 72% (NME1) to 43% (D17S579). Finally, we observed a trend in association between the proportion of loci with LOH and nm23 positivity (chi2 test for trend, p = 0.024). Our findings suggest that genomic alterations in the 17q21-23 region may affect prognosis of CRC as well as regulation of the nm23 protein expression via an unknown underlying mechanism.

Actin-binding cellular proteins inside human immunodeficiency virus type 1

Host proteins are incorporated both on and inside human immunodeficiency virus type 1 (HIV-1) virions. To identify cellular proteins inside HIV-1, virion preparations were treated by a protease-digestion technique that removes external host proteins, allowing for the study of the proteins inside the virus. Treated HIV-1 preparations were analyzed by immunoblot, high-pressure liquid chromatography, and protein sequence analyses. These analyses identified several cellular proteins inside HIV-1: elongation factor 1alpha, glyceraldehyde-3-phosphate dehydrogenase, HS-1, phosphatidylethanolamine-binding protein, Pin1, Lck, Nm23-H1, and the C-terminal tail of CD43. Several of these proteins were found as fragments of their full-sized proteins that appear to be generated by our protease treatment of the virions, the HIV-1 protease, or a cellular protease. Recent advances in cell biology and biochemistry have identified some of these proteins as actin-binding proteins. These results support the hypothesis that actin filaments are incorporated into the virion and may provide additional clues for the understanding of the interaction between viral and cellular proteins during assembly and budding.

Protein markers in colorectal cancer: predictors of liver metastasis

OBJECTIVE

To assess the significance of the expression of five protein markers (nm23, p53, c-erbB-2, u-PA, and VEGF) to the development of metastasis in colorectal cancer.

SUMMARY BACKGROUND DATA

The metastatic cascade is a complex multistep process involving several genetic alterations, angiogenesis activation, and tissue proteolysis. Although the prognosis of colorectal cancer depends on the stage of the tumor, the development of metastasis is difficult to predict.

METHODS

Paraffin-embedded specimens of 58 patients who underwent surgery for colorectal cancer were retrospectively analyzed by immunohistochemistry, and the coexpression of these protein markers was related to patient outcome.

RESULTS

The risk of developing liver secondaries was correlated with the expression of nm23 protein (p < 0.0001); this was also the case in those patients with Dukes' stage B showing positive nm23 immunostaining (p = 0.006). The determination of the number of positive markers or the cumulative intensity score did not improve the predictive value over and above that of nm23 protein alone.

CONCLUSION

Expression of nm23 protein is correlated with the risk of developing liver metastasis. Its evaluation alone may help to determine which patients who have undergone apparently curative resection of a colorectal cancer have an increased risk of liver recurrence, especially those with Dukes' stage B tumors who might be considered for adjuvant chemotherapy.

Heterogeneity of in vitro radiosensitivity in human bladder cancer cells

Human bladder cancer is often heterogeneous containing biologically different populations. Radiotherapy plus chemotherapy is the most common treatment for invasive disease. However few studies have investigated the role of heterogeneity in determining radiosensitivity. The radiation sensitivities of a parent human bladder cancer cell line (UCRU-BL-17CL) and nine cloned cell lines derived from it were determined. These cloned cell lines were previously shown to exhibit different biological characteristics when grown in nude mice. Radiation sensitivity was determined using both MTT and clonogenic assays. The radiobiological parameters, alpha,beta, and surviving fractions at 2 Gy and 8 Gy from the linear-quadratic model, were used to assess radiation sensitivity in the statistical analyses. The nine clones differed in radiosensitivity by both assays. By MTT, but not by the clonogenic assay, their radiation sensitivities were relatively consistent within each of the three biological groups (non-tumorigenic, tumorigenic, invasive); invasive clones were more sensitive than those of the non-tumorigenic and the tumorigenic groups for all the three-test criteria. The heterogeneity exhibited by this cell line may explain some of the variations in the clinical responses seen in the radiation treatment of invasive bladder cancer.

The effect of transfection with Botulinum neurotoxin C1 light chain on exocytosis measured in cell populations and by single-cell amperometry in PC12 cells

We examined the effect on exocytosis in PC12 neuroendocrine cells of transient transfection with the specific endoprotease Botulinum neurotoxin C1 light chain (BoNT/C1), which cleaves syntaxin and SNAP-25. The effects of toxin expression on basal and evoked exocytosis were determined in cell population measurements and also in a single-cell transfection-amperometry assay. Co-expression of BoNT/C1 with human growth hormone (hGH) as a marker of secretory granules in transfected cells resulted in a 95% inhibition of hGH release evoked either by the purinergic agonist ATP or by depolarization with 55 mM K+. In addition, basal hGH release was also inhibited to the same extent. The high level of co-transfection efficiency revealed by this extent of inhibition was exploited in a high-resolution single-cell assay based on cell detection by expression of enhanced green fluorescent protein (EGFP) and analysis of evoked dopamine release by amperometry using a carbon fibre microelectrode. Cells expressing EGFP alone showed population responses and single-cell amperometric responses indistinguishable from those of control non-transfected cells. In contrast, co-expression of BoNT/C1 with EGFP resulted in an almost complete inhibition of current transients due to exocytosis evoked by ATP. These results establish and validate a single-cell assay of transfection-amperometry for analysing the effects of specific proteins on exocytosis.

Correlates of urokinase-type plasminogen activator in colorectal cancer: positive relationship with nm23 and c-erbB-2 protein expression

We undertook a study to analyze the expression of urokinase-type plasminogen activator (u-PA) protein in colorectal cancer (CRC) and to compare it with c-erbB-2 (HER2/neu) and nm23 protein expression. Paraffin-embedded specimens from 58 patients with CRC were retrospectively collected. Immunohistochemical staining of u-PA, c-erbB-2, and nm23 was quantitatively evaluated using a color video image analysis (color VIA) technique. No correlation was found between u-PA expression and tumor stage, age, sex, or tumor site. Although there was no evidence from our data that the level of u-PA in the primary tumors could predict risk of liver metastasis or survival duration, CRC showing overexpression of u-PA (above 85 pixels) had a worse prognosis (P = 0.013). There were significant positive correlations among all three u-PA, c-erbB-2, and nm23 proteins (u-PA vs. c-erbB-2, P = 0.003; u-PA vs. nm23, P < 0.001; c-erbB-2 vs. nm23, P = 0.001), suggesting that, in vivo, all proteins interact or are similarly regulated.

Overexpression of nm23 protein assessed by color video image analysis in metastatic colorectal cancer: correlation with reduced patient survival

The function and prognostic significance of the nm23 gene is controversial in colorectal cancer (CRC). The aim of this study was to determine if nm23 protein expression correlated with the subsequent development of liver metastasis. Paraffin-embedded sections of 30 metastasizing CRC primaries and their subsequently resected liver secondaries were compared with those of 28 nonmetastasizing CRCs, 20 adenomas, and 20 cases of normal colonic mucosa. Expression of nm23 protein, assayed by immunohistochemistry, was measured using a standard semiquantitative scaling system and compared with a microcomputerbased color video image analysis (VIA). There was good correlation between color VIA and semiquantitative evaluation of nm23 immunoreactivity, confirming the validity of quantitative analysis (Pearson's r = 0.88; p < 0.001). Metastasizing CRC primaries and secondaries overexpressed nm23 protein when compared with the other clinical groups, particularly nonmetastasizing CRC (Student's t-test, p < 0.001). Furthermore, more nm23 immunoreactivity was associated with a higher risk of death from CRC (log-rank test, p = 0.002). These results suggest that overexpression of nm23 is highly associated with liver metastases from CRC and reduced survival.

Sequence-specific binding of human immunodeficiency virus type 1 nucleocapsid protein to short oligonucleotides

We have analyzed the binding of recombinant human immunodeficiency virus type 1 nucleocapsid protein (NC) to very short oligonucleotides by using surface plasmon resonance (SPR) technology. Our experiments, which were conducted at a moderate salt concentration (0.15 M NaCl), showed that NC binds more stably to runs of d(G) than to other DNA homopolymers. However, it exhibits far more stable binding with the alternating base sequence d(TG)n than with any homopolymeric oligodeoxyribonucleotide; thus, it shows a strong sequence preference under our experimental conditions. We found that the minimum length of an alternating d(TG) sequence required for stable binding was five nucleotides. Stable binding to the tetranucleotide d(TG)2 was observed only under conditions where two tetranucleotide molecules were held in close spatial proximity. The stable, sequence-specific binding to d(TG)n required that both zinc fingers be present, each in its proper position in the NC protein, and was quite salt resistant, indicating a large hydrophobic contribution to the binding. Limited tests with RNA oligonucleotides indicated that the preferential sequence-specific binding observed with DNA also occurs with RNA. Evidence was also obtained that NC can bind to nucleic acid molecules in at least two distinct modes. The biological significance of the specific binding we have detected is not known; it may reflect the specificity with which the parent Gag polyprotein packages genomic RNA or may relate to the functions of NC after cleavage of the polyprotein, including its role as a nucleic acid chaperone.

Vascular endothelial growth factor expression is reduced in liver metastasis from colorectal cancer and correlates with urokinase-type plasminogen activator

We undertook a retrospective study to investigate the correlation between the expression of vascular endothelial growth factor (VEGF) and urokinase-type plasminogen activator (u-PA) proteins with progression of colorectal carcinoma (CRC). Immunohistochemical analyses using antibodies against VEGF and u-PA were carried out on archival specimens of 58 human colon carcinomas, 30 liver secondaries and 20 adenomas. Expression of VEGF was significantly reduced in the metastatic liver tumours compared with primary ones (Wilcoxon test, P = 0.002), suggesting VEGF activity to be secondarily down-regulated once the tumour cells reach the hepatic parenchyma. There was no strong evidence from our data that the level of VEGF or u-PA in the primary tumour could predict risk of liver metastasis or survival duration. VEGF and u-PA expression were positively correlated in primary CRC suggesting that both proteins may interact in vivo (chi-square test, P = 0.019) in tumour progression.

BIAcore for macromolecular interaction

Examination of the literature for the period of this review revealed nearly two hundred citations that employed surface plasmon resonance (SPR) spectroscopy using BIAcore technology to evaluate biospecific interactions, demonstrating the increasing popularity of this powerful technique. Among these we noted the development of several new applications/modifications of standard techniques. In general, we find the qualitative aspects of the reported experiments to be excellent but the quantitative descriptions (kT, kon, koff, and keq) as well as the binding models still lagging behind.

Correction of the NMR structure of the ETS1/DNA complex

The ETS family of transcription factors consists of a group of proteins that share a highly conserved 85 amino acid DNA-binding domain (DBD). This family recognizes a consensus sequence rich in purine bases with a central GGAA motif. A comparison of the published three-dimensional structures of the DBD/DNA complexes of ETS1 by NMR [Werner et al. (1995) Cell, 83, 761-771] and the related Pu.1 by X-ray crystallography [Kodandapani et al. (1996) Nature, 380, 456-460] reveals an apparent discrepancy in which the protein domains bind with opposite polarity to their target sequences. This surprising and highly unlikely result prompted us to reexamine our NMR structure. Additional NMR experiments now reveal an error in the original interpretation of the spectra defining the orientation of the ETS1-DBD on DNA. It was originally reported that the ETS1-DBD bound to DNA with a bipartite motif involving major groove recognition via a helix-turn-helix element and minor groove recognition via protein side-chain intercalation. The presence of intercalation was deduced on the basis of numerous NOEs between several amino acids in the protein and a resonance at 12.33 ppm originally assigned to a DNA imino proton. New NMR experiments now conclusively demonstrate that this resonance, which is located within the DNA imino proton region of the spectrum, arises from the hydroxyl proton of Tyr86. Realization of this error necessitated reanalysis of the intermolecular NOEs. This revealed that the orientation of the ETS1-DBD in the complex is opposite to that originally reported and that a tryptophan residue does not intercalate into the DNA. The calculation of a new ensemble of structures based on the corrected data indicates that the structure of the ETS1-DBD/DNA complex is indeed similar to the X-ray structure of the Pu.1-DBD/DNA complex.

Adequacy of amino acids in diets fed to lactating dairy cows

The Cornell Net Carbohydrate and Protein System was used to evaluate absorbable limiting amino acids (AA) for milk yield. The system was utilized to characterize whether diets in five previous experiments met AA requirements for milk protein synthesis. Twenty-nine treatment means for milk yield from 367 cows constituted the database for the evaluation. Using the mechanistic relationships of nutrient metabolism described in the Cornell system, absorbed amounts were predicted of each essential AA from a diet and milk yields allowed by the most limiting AA. Regression of observed milk yield (Y) on predicted milk yield (X) using all treatment means (n = 29) was Y = 2.3 + 0.799X (r2 = 0.72). The linear relationship was stronger using 6 treatment means (n = 18) when protein supplements were fed rather than when ruminally protected AA were fed or when AA were postruminally infused (Y = -1.8 + 0.983X; r2 = 0.93). The Cornell system predicted that, for diets based on corn, Met or Lys was limiting when soybean meal was the protein source, but Lys was limiting when corn gluten meal or brewers grains were the source of protein. By AA limitation, the Cornell system explained differences in milk yield for diets that differed in supplemental protein sources in some of the experiments. As determined from milk protein yields in these studies, requirements for individual essential AA were expressed as a percentage of dietary dry matter or total essential AA, and values were relatively constant among dietary treatments and experiments.

Relationship between radiation response and p53 status in human bladder cancer cells

Mutations in the p53 tumour suppressor gene are found at high frequency in bladder cancer. There is strong evidence that p53 plays an important role in controlling the cell cycle after DNA damage by ionizing radiation. However, the effect of loss of p53 function on radiosensitivity is not yet clear. Radiotherapy combined with chemotherapy is the most common treatment for patients with invasive bladder cancer. Recently three bladder cancer cell lines have been established and this paper investigates the p53 status and clonogenic survival of these cell lines following irradiation. It was found that one line expresses wt p53 (UCRU-BL-13) and two lines contain a codon 72 polymorphism (UCRU-BL-17 and UCRU-BL-28). UCRU-BL-17 cells also contain a point mutation affecting codon 280. The level of p53 expression in the cell lines is clearly different, with UCRU-BL-17 expressing a higher level of p53 compared with UCRU-BL-13; UCRU-BL-28 expressed intermediate levels. The clonogenic survival of these cell lines has been determined. It was found that the line expressing a p53 mutation was more sensitive than those with wild type p53, providing support for a model in which loss of p53 function is associated with increased radiosensitivity, possibly due to reduced p53-dependent DNA repair.

Inhibition of vascular endothelial growth factor-induced endothelial cell migration by ETS1 antisense oligonucleotides

Vascular endothelial growth factor (VEGF) increased the level of ETS1 mRNA in human umbilical vein endothelial cells (HUVEC) and human lung microvascular endothelial cells (HMVEC-L) over 5-fold. Protein levels were shown to increase concordantly. VEGF was also found to stimulate the invasiveness of endothelial cells as measured by migration through Matrigel- or gelatin-coated membranes. The VEGF-induced invasiveness was inhibited by ETS1 antisense oligonucleotides but not by a sense control. In addition, the ETS1 antisense oligonucleotides reduced the levels of ETS1 and urokinase-type plasminogen activator mRNAs. The antisense oligonucleotides directed against the ETS1 gene thus altered a cellular property of endothelial cells that is correlated with the ability of the cells to migrate through basement membranes. Together, these observations demonstrate a direct role for the ETS1 gene in angiogenesis.