Fluorescent modification of the cysteine 202 residue of Escherichia coli transcription termination factor rho

The lone cysteine residue (Cys-202) of transcription termination factor rho has been modified with the sulfhydryl-specific dyes 5-iodoacetamidofluorescein and 5-(2-[iodoacetyl)amino)ethyl)aminonaphthalene-1-sulfonic acid. Labeling with both dyes is specific for the Cys-202 residue and is at least 90% complete. Rho protein is an RNA-dependent ATPase and exists as a hexamer of identical subunits in its activated (RNA-liganded) form. We find that chemical modification of rho at Cys-202 does not significantly change the properties of the protein; subunit assembly, RNA binding, and poly(rC)-activated ATP hydrolysis are all relatively unperturbed by the covalent attachment of these fluorescent moieties. On the other hand, the spectral, quenching, and anisotropy properties of the fluorescent groups are all significantly modified by attachment to the protein. No energy transfer is seen between fluorescein-labeled subunits within rho hexamers, indicating that the Cys-202 residues on these subunits are located at least 40 A apart. These fluorescently labeled rho molecules should represent useful probes to study the conformations and inter- and intrasubunit geometries of this termination factor at various stages of its interaction with nascent RNA transcripts.

Effect of cyclosporine on immunologically mediated diabetes in nonobese diabetic mice

Spontaneous diabetes in NOD mice has an immunologically mediated cause and is a T cell-dependent process. When diabetic NOD mice are grafted with cultured BALB/c islet tissue, the islet graft is destroyed by disease recurrence in the graft. Disease recurrence is a CD4 T cell-dependent process as determined by in vivo administration of anti-CD4 or anti-CD8 monoclonal antibody prior to the grafting of islet tissue. Cyclosporine functions in the early sequence of T cell activation by regulating the production of messenger RNA for lymphokines synthesis. Cyclosporine does not inhibit the synthesis of lymphokine once the lymphokine message is present in the cell. Thus, we might expect cyclosporine to be relatively inefficient as an agent for the regulation of disease recurrence following transplantation to actively diabetic recipients, and we would expect cyclosporine to be more effective when administered before the onset of the disease. Low-dose cyclosporine treatment can prevent development of the disease when the drug is administered before the onset of disease. Data presented here show that cyclosporine is ineffective in controlling disease recurrence in the islet graft transplanted to actively diabetic animals. Also, when we eliminate CD4 T cells from the diseased animals and graft islet tissue prior to the administration of cyclosporine, we are unable to maintain a graft with low-dose cyclosporine therapy. This result leads us to conclude that, although anti-CD4 treatment controls the expression of the disease process and allows the survival and function of the islet graft, this treatment does not return diseased animals to the prediabetic condition in which the development of diabetes can be controlled by low-dose cyclosporine therapy.

A cell type-specific enhancer drives expression of the chick muscle acetylcholine receptor alpha-subunit gene

The regulation of acetylcholine receptor alpha-subunit gene expression was analyzed by transient expression assays. Using rabbit beta-globin cDNA as a reporter gene, we have confirmed that the 5'-flanking sequence of the chicken acetylcholine receptor alpha-subunit gene directs specific expression in differentiated C2C12 cells, a mouse muscle cell line, but not in undifferentiated C2C12 cells and mouse 3T3 fibroblasts. Testing chimeric plasmids containing Bal31 deletion mutants of the alpha-subunit gene upstream sequence, we found the -116 to -81 region of the alpha-subunit to be responsible for tissue- and stage-specific expression. This 36 bp fragment stimulates the activity of both alpha-subunit and SV40 promoters in a distance- and orientation-independent manner, thus fulfilling the criteria of an enhancer.

Isolation, structure and expression of cDNA and genomic clones for murine eosinophil differentiation factor. Comparison with other eosinophilopoietic lymphokines and identity with interleukin-5

Eosinophil differentiation factor (EDF) is a recently described regulator affecting eosinophil growth and activation. cDNA clones for murine EDF were isolated by direct expression from libraries prepared from the T cell hybrid NIMP-TH1. The longest cDNA clone obtained was 1534 bp in length encoding a polypeptide of 133 amino acids. Two variant cDNAs suggesting alternative RNA processing events were detected. The EDF gene was cloned from a genomic lambda library and a region of 6727 bp encompassing the gene was sequenced. The gene contains three introns 829, 1875 and 79 bases in length and has numerous repetitive sequences. A common, possible regulatory element, including a conserved decamer, lies adjacent to the TATA boxes of the EDF and granulocyte-macrophage colony-stimulating factor (GM-CSF) genes and similar sequences are present in some other lymphokine genes. Recombinant EDF produced in monkey COS cells strongly stimulated the eosinophil lineage and also showed B-cell-growth factor II (BCGFII) activity whereas recombinant murine interleukin-3 and GM-CSF showed much broader activity towards the different myeloid lineages, were less active on eosinophils and had no BCGFII activity. The BCGFII activity of recombinant EDF together with a comparison of the BCGFII (interleukin-5) cDNA sequence with that of the EDF cDNA establishes that these two activities are the properties of a single polypeptide.

Enhanced vasopressin (V2-receptor)-induced sodium retention in mineralocorticoid hypertension

The deoxycorticosterone acetate (DOCA)-Na model of hypertension requires the presence of vasopressin for expression of high blood pressure. In the present study, the effects of vasopressin V2-receptor stimulation were examined in kidneys from rats receiving 1 wk of DOCA-Na or control (olive oil-tap water) treatment. The dose response to vasopressin (10(-10) to 10(-6) M) was tested in microdissected cortical collecting tubule (CCT) segments and adenosine 3',5'-cyclic monophosphate (cAMP) accumulation was significantly increased in segments from DOCA-Na rats vs. controls, confirming our previous study. In other experiments, kidneys from DOCA-Na and control rats were perfused with a modified Krebs-Henseleit buffer (37 degrees C, pH 7.4) and treated with either vehicle or 0.21-2.1 pM 1-desamino-8-D-arginine vasopressin (DDAVP). DDAVP caused significant (P less than 0.05) dose-related reductions in urine excretion (UV) and urinary sodium excretion (UNaV) in both DOCA-Na and control kidneys in the absence of changes in renal hemodynamics. However, DDAVP produced earlier and significantly greater reductions in UV and UNaV in kidneys from DOCA-Na vs. control rats. Percent fractional excretion of sodium was reduced significantly only in the DOCA-Na group (2.1 pM DDAVP). A small degree of antikaluresis was seen with DDAVP in both groups. Thus, DOCA-Na treatment augmented cAMP accumulation in the CCT, accompanied by a significant enhancement of DDAVP-stimulated urinary sodium and water reabsorption at the level of the intact kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Demonstration of rat preprotachykinin A mRNA in the rat trigeminal ganglion by in situ hybridization histochemistry

The localization of gamma-preprotachykinin A mRNAs in the rat trigeminal ganglion was demonstrated by in situ hybridization histochemistry using the 32P and 35S labelled gamma-preprotachykinin A complementary DNA. In situ hybridization using 32P allowed shorter exposure times, whereas higher resolution of the hybridization signal on both film and emulsion autoradiograms was obtained using 35S. Preprotachykinin A mRNA detected by the gamma-preprotachykinin A probe was localized in about 15 per cent of the trigeminal ganglion cells, most of which were small or medium sized. Immunohistochemical studies using anti-substance P antibodies demonstrated that 15-20 per cent of total trigeminal ganglion cells were positive. These cells were small or medium sized. The result of immunohistochemistry coincided well with that of in situ hybridization histochemistry. The present study showed that the cellular localization of preprotachykinin A mRNA could be analysed by in situ hybridization histochemistry.

Some rules for predicting the base-sequence dependence of DNA conformation

Two tables have been constructed showing the crystal and solution conformations of short sequences of DNA. Each of these DNAs has been found to be in one of three different conformations--the A, B, or Z form--depending upon the base sequence and the environmental conditions. A set of rules is presented showing the tendency of certain base pairs to direct the DNA conformation into the A, B, or Z genus in saturated salt solutions and in crystals. These rules are based on a consideration of nearest-neighbor interactions that are interpreted in terms of 10 different two-letter code words made from the letters denoting the bases guanine (G), cytosine (C), adenine (A), and thymine (T). One table discusses the effect on DNA conformation of 3 strong words that tend to direct a DNA oligomer into either the A, B, or Z genus in crystals or in aqueous solutions containing a high salt concentration (6 M). The second table discusses the remaining 7 code words that appear to have a much weaker effect on conformation. The sequences that are most likely to lead to A-Z, B-Z, and A-B junctions are discussed, as is the possible biological significance of these rules.

Deoxycytidylate hydroxymethylase gene of bacteriophage T4. Nucleotide sequence determination and over-expression of the gene

We describe two approaches to cloning and over-expressing gene 42 of bacteriophage T4, which encodes the early enzyme deoxycytidylate hydroxymethylase. In Bochum a library of sonicated fragments of wild-type phage DNA cloned into M13mp18 was screened with clones known to contain parts of gene 42. Two overlapping fragments, each of which contained one end of the gene, were cleaved at a HincII site and joined, to give a fragment containing the entire gene. In Corvallis a 1.8-kb fragment of cytosine-substituted DNA, believed to contain the entire gene, was cloned into pUC18 and shown to express the enzyme at low level. The cloned fragment bore an amber mutation in gene 42. From the DNA sequence of gene 42, the cloned gene was converted to the wild-type allele by site-directed mutagenesis. Both gene-42-containing fragments were cloned into the pT7 expression system and found to be substantially overexpressed. dCMP hydroxymethylase purified from one of the over-expressing strains had a turnover number similar to that of the enzyme isolated earlier from infected cells. In addition, the N-terminal 20 amino acid residues matched precisely the sequence predicted from the gene sequence. The amino acid sequence of gp42 bears considerable homology with that of thymidylate synthase of either host or T4 origin. The gene 42 nucleotide sequences of bacteriophages T2 and T6 were determined and found to code for amino acid sequences nearly identical to that of T4 gp42.

Fused cells of frog proximal tubule: II. Voltage-dependent intracellular pH

Experiments were performed in intact proximal tubules of the doubly perfused kidney and in fused proximal tubule cells of Rana esculenta to evaluate the dependence of intracellular pH (pHi) on cell membrane potential applying pH-sensitive and conventional microelectrodes. In proximal tubules an increase of the K+ concentration in the peritubular perfusate from 3 to 15 mmol/liter decreased the peritubular cell membrane potential from -55 +/- 2 to -38 +/- 1 mV paralleled by an increase of pHi from 7.54 +/- 0.02 to 7.66 +/- 0.02. The stilbene derivative DIDS hyperpolarized the cell membrane potential from -57 +/- 2 to -71 +/- 4 mV and led to a significant increase of the K+-induced cell membrane depolarization, but prevented the K+-induced intracellular alkalinization. Fused proximal tubule cells were impaled by three microelectrodes simultaneously and cell voltage was clamped stepwise while pHi changes were monitored. Cell membrane hyperpolarization acidified the cell cytoplasm in a linear relationship. This voltage-induced intracellular acidification was reduced to about one-third when HCO-3 ions were omitted from the extracellular medium. We conclude that in proximal tubule cells pHi depends on cell voltage due to the rheogenicity of the HCO-3 transport system.

[Multifactorial analysis of survival in breast cancer]

Eleven clinical and pathological factors were eligible for study in relation to the survival of 617 female patients with breast cancer treated by radical mastectomy. All the patients have been followed for more than five years. The data were analyzed by the Cox's proportional hazards regression model. A final set of five independent significant prognostic factors was obtained. In order of importance, they were clinical stage, age at diagnosis, axillary lymph node status, histologic type and size of the primary. To test the time-dependency of these factors using Cox's model, all except age reduced their prognostic impact significantly after five years, however, age was a powerful prognostic factor for long-term survival. A prognostic index based on the regression coefficients was constructed. This index can give a better prediction for our patients' survival and be taken as reference when formulating treatment protocols for breast cancer.

ACR-NEMA digital imaging and communications standards: minimum requirements

The purposes, implications, and history of development of the American College of Radiology-National Electrical Manufacturers Association (ACR-NEMA) Digital Imaging and Communication Standard and its contents are briefly described, and the minimum requirements of the ACR-NEMA Digital Imaging and Communication Standard are described with a concise introduction of each layer. The usefulness, validity, current status, and future development of the standard are also discussed.

The effects of acetaldophosphamide, a novel stable aldophosphamide analogue, on normal human and leukemic progenitor cells in vitro: implications for use in bone marrow purging

Acetaldophosphamide (A-ALD), a novel in vitro active and stable derivative of aldophosphamide, kills human bone marrow-derived granulocyte-macrophage colony-forming cells (GM-CFC) independent of the cell cycle. The surviving fraction of GM-CFC is an exponential function of the drug concentration and time of exposure. Variation of marrow light-density cell concentration between 2 x 10(6) and 10 x 10(6)/ml does not significantly influence its GM-CFC toxicity. Marrow depleted of GM-CFC by A-ALD subsequently generates GM-CFC when grown in suspension cultures. During the early period after treatment with A-ALD the number of surviving GM-CFC (size of surviving GM-CFC compartment) does influence the speed of the GM-CFC repopulation in suspension cultures. The importance of the number of surviving GM-CFCs for the growth and maintenance of GM-CFC population in such suspension cultures diminishes with time. No significant differences are observed after 2 wk, indicating that the ancestor stem cell population and its regenerative potential responsible for in vitro hematopoiesis have not been significantly affected by the drug treatment. A-ALD-treated progenitor cells retain their ability to integrate with the previously established marrow stromal cell layer and generate GM-CFC within this layer to an extent comparable to that of untreated marrow cells. The effect of A-ALD on human hematopoiesis is comparable to that of 4-hydroperoxycyclophosphamide. Its advantage over 4-hydroperoxycyclophosphamide is a greater stability in vitro. It has sparing effect on GM-CFC ancestor cells. Its toxicity to myeloid leukemia cell line (KBM-3)-derived clonogeneic cells is higher than to the GM-CFC. It is similar in doxorubicin-sensitive (KBM-3) and -resistant (KBM-3/DOX) leukemic cells. Thus, A-ALD appears to be a promising drug for in vitro purging of bone marrow cells.

Clinical report on 62 cases of acute dimethyl sulfate intoxication

Sixty-two cases of accidental acute intoxication from the inhalation of dimethyl sulfate (DMS) are reported. To facilitate clinical evaluation and treatment, as well as identification of capacity for physical labor, a grading system was established according to the history of exposure to DMS, symptoms and signs of respiratory mucosal irritation, findings on chest radiographs, and abnormalities of leukocyte count. Emergency treatment included prophylactic use of glucocorticoids, supplemental oxygen, sedatives, and antibiotics for prevention and treatment of laryngeal and pulmonary edema, pulmonary infections, and other complications. Follow-up studies for 2-12 years have found only mild to moderate impairment in ventilatory capacity in eight cases, with no abnormal findings in ECG, chest films, and routine blood tests. Nearly all patients have resumed their usual work.

Microwave-induced thermoelastic pressure wave propagation in the cat brain

This paper presents direct measurements of acoustic pressure wave propagation in cat brains irradiated with pulsed 2.45-GHz microwaves. Short rectangular microwave pulses (2 microseconds, 15 kW peak power) were applied singly through a direct-contact applicator located at the occipital pole of a cat's head. Acoustic pressure waves were detected by using a small hydrophone transducer, which was inserted stereotaxically into the brain of an anesthetized animal through a matrix of holes drilled on the skull. The measurements clearly indicate that pulsed microwaves induce acoustic pressure waves which propagate with an acoustic wave velocity of 1523 m/s.

Role of the L3T4+ T cell in allograft rejection

Pancreatic islet and fetal pancreas allotransplantation has been used to examine the role of the L3T4+ T cell in allograft rejection. Tissues were grafted into recipient animals depleted of peripheral L3T4+ T cells by in vivo administration of GK1.5 (anti-L3T4) monoclonal antibody to ask the question: is there a requirement for the L3T4+ T cell in graft rejection? Data show that the requirement for the L3T4+ T cell depends on either the type of tissue transplanted or type of the antigenic disparity between donor and recipient. Data also indicate that islet allograft acceptance achieved after GK1.5 treatment of the recipient is not due to tolerance induction. We therefore conclude that the cellular requirements for allograft rejection are determined by the type of tissue transplanted and the genetic disparity between donor and recipient.

Role of the L3T4+ T cell in allograft rejection

Pancreatic islet and fetal pancreas allotransplantation has been used to examine the role of the L3T4+ T cell in allograft rejection. Tissues were grafted into recipient animals depleted of peripheral L3T4+ T cells by in vivo administration of GK1.5 (anti-L3T4) monoclonal antibody to ask the question: is there a requirement for the L3T4+ T cell in graft rejection? Data show that the requirement for the L3T4+ T cell depends on either the type of tissue transplanted or type of the antigenic disparity between donor and recipient. Data also indicate that islet allograft acceptance achieved after GK1.5 treatment of the recipient is not due to tolerance induction. We therefore conclude that the cellular requirements for allograft rejection are determined by the type of tissue transplanted and the genetic disparity between donor and recipient.

Formation of protein kinase recognition sites by covalent modification of the substrate. Molecular mechanism for the synergistic action of casein kinase II and glycogen synthase kinase 3

The mechanism for synergistic phosphorylation by glycogen synthase kinase 3 (GSK-3) and casein kinase II was studied using a synthetic peptide which contains the sequence of a potentially important proline/serine-rich regulatory region of rabbit muscle glycogen synthase. The peptide, Ac-PRPAS(3a)VPPS(3b)PSLS(3c)RHSS(4)PHQS(5) EDEEEP-amide, has five known phosphorylation sites of the native enzyme designated sites 3a, 3b, 3c, 4, and 5, which are spaced every fourth residue. The peptide was phosphorylated specifically at site 5 by casein kinase II with an apparent Km of 23 microM, but it was not phosphorylated by GSK-3. However, after initial phosphorylation of site 5 by casein kinase II, the peptide became an effective substrate for GSK-3 with an apparent Km of 2 microM. GSK-3 introduced up to four phosphates and appeared to catalyze the sequential modification of sites 4, 3c, 3b, and 3a, respectively. The results can be explained if GSK-3 recognizes the sequence -SXXXS(P). Phosphorylation of site 5 by casein kinase II creates this recognition site. Thereafter, each successive phosphorylation introduced by GSK-3 generates a new recognition site. The results provide a molecular basis to explain the synergistic action of casein kinase II and GSK-3 that is also observed with native glycogen synthase. In addition, this investigation emphasizes how protein recognition sites in some cellular targets may have to be formed post-translationally.

Cloning and expression in Escherichia coli of chromosomal mercury resistance genes from a Bacillus sp

A 7.9-kilobase (kb) chromosomal fragment was cloned from a mercury-resistant Bacillus sp. In Escherichia coli, in the presence of a second plasmid carrying functional transport genes, resistance to HgCl2 and to phenylmercury acetate (PMA) was expressed. Shortening the cloned fragment to 3.8 kb abolished resistance to PMA but not to HgCl2. In Bacillus subtilis, the 3.8-kb fragment produced mercuric reductase constitutively but did not produce resistance to HgCl2 or to PMA.

Genetic correlation of ethanol-induced ataxia and cerebellar Purkinje neuron depression among inbred strains and selected lines of rats

In the present study, we compared phenotypic differences in behavioral and neurophysiological responses to acute ethanol administration among six inbred rat strains. Genetic variation was found both for ataxia, as measured by loss of righting response (sleep time) after a hypnotic dose of ethanol, and for the depressant action of ethanol on the spontaneous discharge of cerebellar Purkinje neurons. Results from an analysis of covariance of these phenotypes, measured among the inbred strains, provided strong evidence for a high genetic correlation between sleep time and inhibition of cerebellar Purkinje neuron discharge in response to acute ethanol administration. However, ethanol metabolism was also found to correlate with the behavioral sensitivity of rats to ethanol. Preliminary data from the third generation of replicate lines of rats currently being selectively bred for high and low acute sensitivity to ethanol shows a trend toward divergence of both ethanol sleep time and neuronal sensitivity to acute ethanol. The conclusion from these data supports the hypothesis that the cerebellum is an important locus of ethanol action, and suggests that neuronal sensitivity to ethanol will continue to diverge between these rat lines as selection for the sleep time phenotype progresses.

A 90 degrees optical fiber hybrid for optimal signal power utilization

An optical 90 degrees hybrid comprising a single-mode fiber coupler and a polarization beam splitter was made at 0.82 microm. It relies on the phase retardation intentionally induced in one of the input fiber leads of the coupler. By properly choosing the transmission/coupling coefficient as well as the orientation of the polarization beam splitter following the coupler, optimum distribution of the available optical fields can be obtained in a Costas loop.

Sequence dependent conformations of oligomeric DNA's in aqueous solutions and in crystals

In order to determine the sequence dependence of the conformation of deoxynucleotides, Raman spectra have been obtained for the following oligodeoxynucleotides in aqueous salt solutions and in crystals: d(CpG)(I), d(TGCGCGCA)(II), d(CACGCGTG)(III), d(CGTGCACG)(IV), d(CGCATGCG)(V), d(ACGCGCGT)(VI), d(CGCGTACGCG)(VII), d(CGCACGTGCG)(VIII) and d(CGTGCGCACG)(IX), d(GCTATAGC) (X), d(GCATATGC) (XI), d(GGTATACC) (XII) and d(GGATATCC) (XIII). The normal B type conformation is observed for all the oligomer DNA's at low salt (0.1-1.0 M NaCl) concentration in the temperature range of 0-25 degrees C. It was considered possible that all of the first nine oligomers could go into the Z form in aqueous high salt (5.0-6.0 M NaCl) solutions, and under these conditions the last four were considered candidates to go into the A form. The B-type conformation was found to exist in high salt solutions for (I), (IV), (V), (VI), (X), (XI) and (XIII); the Z or partial Z conformation appears in high salt solution for the oligomers, (II), (III), (VII), (VIII) and (IX); an A or partial A conformation appears in high salt solution for (XII). In the crystalline state, (IV), (VIII), (X), and (XI) stay in the B-form and all of the other oligomers adopt the complete Z-form except for (XII) which crystallizes in the A form. In both the crystal and in aqueous solutions, the identification of the conformation genus was made by means of Raman spectroscopy. In the crystal of (I), grown at pH7.0, guanosine is found to be in C3'-endo/syn conformation and cytidine in C2'-endo/anti, which may be taken as the ideal building block of the typical Z conformation. At pH4, (I) crystallizes in a conformation similar to the B genus. A study of the thermally induced B to Z transition has been carried out for (II) and (III). Based on the analysis of Raman spectra of the alternating pyrimidine-purine oligomers which might be expected to go into the Z form, the tendency for these oligonucleotides to adopt the Z form can be ranked as: d(CGCGCGCG) greater than (II) greater than (III) greater than (V) approximately (VI) greater than (IV) for octamers and (VII) greater than (VIII) greater than (IX) for the decamers. Similarly, those oligomers which might have a tendency to go into the A form could be ranked as (XII) greater than (XIII) approximately (X) greater than (XI). These data should provide help in formulating rules for predicting the sequence dependence of the B to A and B to Z transitions. Some possible rules are explored, but precautions should be taken.

Clinical application of laser Doppler flowmetry for measurement of cutaneous circulation in health and disease

The cutaneous laser Doppler device (LDF) was employed to determine its usefulness in differentiating the circulation of the feet in normal subjects from that in patients with arteriosclerosis obliterans. It is shown that the laser Doppler frequencies correlated well with results from venous occlusion plethysmography, which measured volume rate of flow. Thus, one can determine volume rate of flow by the simple Doppler method. There was a linear relationship between these two methods of measurements. Using the LDF method, it was determined that normal individuals have toe flows that on the average are 42% of finger flows in supine resting subjects. In peripheral vascular disease of the lower extremities, the LDF measurements showed a decreased circulation in the large toes when the patients are supine and the lower extremities flat. The results between health and disease are exaggerated by elevating the feet, at which time the diseased circulation falls to extremely low values compared with those of normal subjects. A similar decrease in skin oxygen tension in the diseased lower extremities was observed when the limbs were elevated.

A tissue-specific transcriptional enhancer is found in the body of the HLA-DR alpha gene

We mapped cis-acting regulatory elements in the HLA-DR alpha gene, which encodes the monomorphic subunit of the HLA-DR heterodimer. Genomic fragments of HLA-DR alpha were placed 5' or 3' to the chloramphenicol acetyltransferase reporter gene, the transcription of which was initiated from the Herpes simplex thymidine kinase promoter. In transient expression assays, fragments from the body of the HLA-DR alpha gene were able to increase chloramphenicol acetyltransferase activity in a position-, orientation-, and promoter-independent yet tissue-specific fashion. These HLA-DR alpha cis-acting regulatory elements contain previously identified DNase I-hypersensitive sites and DNA sequences homologous to those found in other eukaryotic transcriptional enhancers.

Mapping structurally perturbed sites in DNA by replication arrest and run-off replication

We describe a technique for rapid fine mapping of sites of torsion-induced perturbations of DNA structure. The technique involves strand scission or chemical base modification at structurally perturbed sites, replication arrest in a double-strand DNA sequencing reaction, and size analysis of replication products by electrophoresis on sequencing gels. Besides being less complicated and faster than site identification by conventional end-labeling methods, the technique assures high sequence specificity through the use of oligomeric sequencing primers. This property should be useful for in vivo mapping of DNA structural perturbations with known sequence within complex genomes.