Higher transfection efficiency of genomic DNA purified with a guanidinium thiocyanate-based procedure

Trop-2 cleavage by ADAM10 is an activator switch for cancer growth and metastasis

Trop-2 is a transmembrane signal transducer that can induce cancer growth. Using antibody targeting and N-terminal Edman degradation, we show here that Trop-2 undergoes cleavage in the first thyroglobulin domain loop of its extracellular region, between residues R87 and T88. Molecular modeling indicated that this cleavage induces a profound rearrangement of the Trop-2 structure, which suggested a deep impact on its biological function. No Trop-2 cleavage was detected in normal human tissues, whereas most tumors showed Trop-2 cleavage, including skin, ovary, colon, and breast cancers. Coimmunoprecipitation and mass spectrometry analysis revealed that ADAM10 physically interacts with Trop-2. Immunofluorescence/confocal time-lapse microscopy revealed that the two molecules broadly colocalize at the cell membrane. We show that ADAM10 inhibitors, siRNAs and shRNAs abolish the processing of Trop-2, which indicates that ADAM10 is an effector protease. Proteolysis of Trop-2 at R87-T88 triggered cancer cell growth both in vitro and in vivo. A corresponding role was shown for metastatic spreading of colon cancer, as the R87A-T88A Trop-2 mutant abolished xenotransplant metastatic dissemination. Activatory proteolysis of Trop-2 was recapitulated in primary human breast cancers. Together with the prognostic impact of Trop-2 and ADAM10 on cancers of the skin, ovary, colon, lung, and pancreas, these data indicate a driving role of this activatory cleavage of Trop-2 on malignant progression of tumors.

A seven-gene CpG-island methylation panel predicts breast cancer progression

Background

DNA methylation regulates gene expression, through the inhibition/activation of gene transcription of methylated/unmethylated genes. Hence, DNA methylation profiling can capture pivotal features of gene expression in cancer tissues from patients at the time of diagnosis. In this work, we analyzed a breast cancer case series, to identify DNA methylation determinants of metastatic versus non-metastatic tumors.

Methods

CpG-island methylation was evaluated on a 56-gene cancer-specific biomarker microarray in metastatic versus non-metastatic breast cancers in a multi-institutional case series of 123 breast cancer patients. Global statistical modeling and unsupervised hierarchical clustering were applied to identify a multi-gene binary classifier with high sensitivity and specificity. Network analysis was utilized to quantify the connectivity of the identified genes.

Results

Seven genes (BRCA1, DAPK1, MSH2, CDKN2A, PGR, PRKCDBP, RANKL) were found informative for prognosis of metastatic diffusion and were used to calculate classifier accuracy versus the entire data-set. Individual-gene performances showed sensitivities of 63–79 %, 53–84 % specificities, positive predictive values of 59–83 % and negative predictive values of 63–80 %. When modelled together, these seven genes reached a sensitivity of 93 %, 100 % specificity, a positive predictive value of 100 % and a negative predictive value of 93 %, with high statistical power. Unsupervised hierarchical clustering independently confirmed these findings, in close agreement with the accuracy measurements. Network analyses indicated tight interrelationship between the identified genes, suggesting this to be a functionally-coordinated module, linked to breast cancer progression.

Conclusions

Our findings identify CpG-island methylation profiles with deep impact on clinical outcome, paving the way for use as novel prognostic assays in clinical settings.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1412-9) contains supplementary material, which is available to authorized users.

Long-range transcriptome sequencing reveals cancer cell growth regulatory chimeric mRNA

mRNA chimeras from chromosomal translocations often play a role as transforming oncogenes. However, cancer transcriptomes also contain mRNA chimeras that may play a role in tumor development, which arise as transcriptional or post-transcriptional events. To identify such chimeras, we developed a deterministic screening strategy for long-range sequence analysis. High-throughput, long-read sequencing was then performed on cDNA libraries from major tumor histotypes and corresponding normal tissues. These analyses led to the identification of 378 chimeras, with an unexpectedly high frequency of expression (≈2 x 10(-5) of all mRNA). Functional assays in breast and ovarian cancer cell lines showed that a large fraction of mRNA chimeras regulates cell replication. Strikingly, chimeras were shown to include both positive and negative regulators of cell growth, which functioned as such in a cell-type-specific manner. Replication-controlling chimeras were found to be expressed by most cancers from breast, ovary, colon, uterus, kidney, lung, and stomach, suggesting a widespread role in tumor development.

The Trop-2 signalling network in cancer growth

Our findings show that upregulation of a wild-type Trop-2 has a key controlling role in human cancer growth, and that tumour development is quantitatively driven by Trop-2 expression levels. However, little is known about the regulation of expression of the TROP2 gene. Hence, we investigated the TROP2 transcription control network. TROP2 expression was shown to depend on a highly interconnected web of transcription factors: TP63/TP53L, ERG, GRHL1/Get-1 (grainyhead-like epithelial transactivator), HNF1A/TCF-1 (T-cell factor), SPI1/PU.1, WT (Wilms' tumour)1, GLIS2, AIRE (autoimmune regulator), FOXM1 (forkhead box M1) and FOXP3, with HNF4A as the major network hub. TROP2 upregulation was shown to subsequently drive the expression and activation of CREB1 (cyclic AMP-responsive-element binding protein), Jun, NF-κB, Rb, STAT1 and STAT3 through induction of the cyclin D1 and ERK (extracellular signal regulated kinase)/MEK (MAPK/ERK kinase) pathways. Growth-stimulatory signalling through NF-κB, cyclin D1 and ERK was shown to require an intact Trop-2 cytoplasmic tail. Network hubs and interacting partners are co-expressed with Trop-2 in primary human tumours, supporting a role of this signalling network in cancer growth.

Development of a direct DNA extraction protocol for real-time PCR detection of Giardia lamblia from surface water

Giardia lamblia is one of the most recognized waterborne protozoan parasites causing gastrointestinal disease. A simple but effective DNA extraction protocol for real-time PCR detection from surface water samples was developed in this study. Eleven protocols were compared, which consisted of freeze-thaw treatments (liquid N(2) and boiling water) and purification using the Qiagen DNeasy kit, together with different combinations of proteinase K, PVP360, GITC and Chelex 100 incubation. Using concentrated surface water samples spiked with G. lamblia cysts, the necessary steps for high DNA recovery were shown to be freeze-thaw, DNeasy purification and Chelex 100 incubation. Multiple rounds of freeze-thaw treatment (five cycles per round) were reported for the first time in this study to significantly increase the DNA yield from G. lamblia cysts, from ~20% after one round of freeze-thaw to 40 and 70% after two and three-rounds of freeze-thaw, respectively. More than three rounds of freeze-thaw treatment did not promote additional DNA recovery. The final protocol included three-three-rounds of freeze-thaw treatment, DNeasy purification and Chelex 100 incubation. This method was simpler, more cost-effective, and had a comparable DNA recovery to methods involving immunomagnetic separation.

Trop-1 are conserved growth stimulatory molecules that mark early stages of tumor progression

BACKGROUND

Trop-1 is a cell-cell adhesion regulatory molecule that is overexpressed by a large fraction of tumors in man.

METHODS

To identify fundamental, conserved functional features of Trop-1 in transformed cells, a search was performed for evolutionarily conserved structure, expression patterns, and function by gene cloning, DNA array and serial analysis of gene expression (SAGE), Northern and Western blotting, flow cytometry, and immunohistochemistry of sequential stages of tumor progression in experimental systems and in man.

RESULTS

TROP1 genes demonstrate conserved structure and promoter regions with parallel expression patterns (high expression in the small intestine and colon; lower expression in prostate, thyroid, salivary glands, breast, kidney, lung, liver, and spleen; very low levels in skin and stomach; no expression in heart, muscle, and brain). Progenitor cells of different tissues were shown to express Trop-1. Hence, the expression and functional role of Trop-1 were analyzed at successive stages of tumor progression in vitro and in vivo. The findings show that Trop-1 is expressed at early stages of tumor development, eg, in dysplastic lesions and immortalized cells, is sufficient to stimulate cell growth of expressing transformed cells, and is required for tumor growth in vivo.

CONCLUSIONS

The findings identify Trop-1 as a novel determinant of cell growth at early stages of tumor development and as a marker of early stages of development in normal tissues and in cancer, making this molecule a candidate for novel diagnostic and therapeutic procedures.

Protocol for high-sensitivity/long linear-range spectrofluorimetric DNA quantification using ethidium bromide

Ethidium bromide (EtBr) is the most widely used fluorescent dye in nucleic acid gel electrophoresis since decades. However, it has been essentially forgotten in DNA quantification by spectrofluorimetry. While investigating sensitivity and dynamic range of available fluorochromes, we found that EtBr permits much more sensitive fluorimetric measurements than previously thought. We report here a revised, accurate, and easy-to-use protocol for EtBr-based DNA quantification in solution, which usefully complements the widely used indirect quantification on agarose gels.

Small fragment homologous replacement-mediated modification of genomic beta-globin sequences in human hematopoietic stem/progenitor cells

An ultimate goal of gene therapy is the development of a means to correct mutant genomic sequences in the cells that give rise to pathology. A number of oligonucleotide-based gene-targeting strategies have been developed to achieve this goal. One approach, small fragment homologous replacement (SFHR), has previously demonstrated disease-specific genotypic and phenotypic modification after introduction of small DNA fragments (SDFs) into somatic cells. To validate whether the gene responsible for sickle cell anemia (beta-globin) can be modified by SFHR, a series of studies were undertaken to introduce sickle globin sequences at the appropriate locus of human hematopoietic stem/progenitor cells (HSPCs). The characteristic A two head right arrow T transversion in codon 6 of the beta-globin gene was indicated by restriction fragment length polymorphic (RFLP) analysis of polymerase chain reaction (PCR) products generated by amplification of DNA and RNA. At the time of harvest, it was determined that the cells generally contained </=1 fragment per cell. Control studies mixing genomic DNA from nontransfected cells with varying amounts of the targeting SDFs did not indicate any PCR amplification artifacts due to the presence of residual SDF during amplification. RNA was analyzed after DNase treatment, thus eliminating the potential for SDF contamination. Stable SFHRmediated conversion of normal (beta (A)) to sickle (beta (S)) globin was detected at frequencies up to 13% in cells harvested 30-45 days posttransfection. The minimum conversion efficiency ranged from 0.2 to 3%, assuming modification of at least one cell per experiment showing conversion. Conversion of sickle (beta (S)) to normal (beta (A)) globin was detected up to 10 days posttransfection in lymphoblastoid cells from a sickle cell patient. These studies suggest that SFHR may be effective for ex vivo gene therapy of sickle cells in a patient's HSPCs before autologous transplantation.

Detection of Burkholderia cepacia DNA from artificially infected EDTA-blood and lung tissue comparing different DNA isolation methods

Bacterial DNA (Burkholderia cepacia) was prepared from artificially infected equine ethylenediaminetetraacetic acid (EDTA)-blood and lung tissue by using four standard methods (lysis buffer containing proteinase K, phenol/chloroform/isoamylalcohol-extraction, microwave-treatment, heat treatment) and six commercially available kits (Puregene, High Pure PCR Template Preparation Kit, InstaGene, QiaAmp Tissue Kit, DNAzol and Elu-Quik). After a subsequent polymerase chain reaction (PCR), their efficacy and sensitivity were compared. Concerning the detection limits, the simple lysis with a proteinase K-containing buffer led to the best results for EDTA-blood as well as for artificially infected lung tissue.

Effects of chemical carcinogens and physicochemical factors on the UV spectrophotometric determination of DNA

The ultraviolet (UV) absorbance ratio of 260/280 nm has been used as an indicator of DNA purity. However, the A260/A280 ratio may be beyond the normal range (1.8-1.9) due to physicochemical alterations produced by pH and temperature, and carcinogenic chemical modification. When the pH of the DNA solution buffer increased from 3 to 11, the A260/A280 ratio changed significantly from 1.5 to 2.2 in mixtures of DNA bases [A:T:C:G = 28.5:28.5: 21.5:21.5, i.e., (A + T)/(all four bases) = 57%, expressed as mole percent], of deoxyribonucleosides (adenosine:thymidine:cytidine:guanosine= 28.5:28.5:21.5:21.5, as mole percent), or of deoxyribonucleotides (dAMP:dTMP:dGMP:dCMP = 28.5:28.5:21.5:21.5, as mole percent) examined. The A260/A280 ratio increased with RNA contamination and exceeded 1.9 when RNA concentration was >30%, as mole percent. In contrast, the A260/A280 ratio was linearly reduced by increasing the protein concentration. Phenol (>0.02%) contamination also reduced the A260/A280 ratio to below 1.8. Benzo[a]pyrene diol epoxide (BPDE), a reactive carcinogen metabolite of benzo[a]pyrene (BaP), decreased the A260/A280 ratio correlated with the degree to which it modified the DNA. These results suggest that the UV A260/A280 ratio is significantly affected by pH and the presence of contaminating species of macromolecules and chemicals.

A novel nucleus-targeted protein is expressed in barley leaves during senescence and pathogen infection

The barley (Hordeum vulgare) cDNA HvS40 represents a gene with enhanced mRNA level during leaf senescence. Biolistic transformation of onion (Allium cepa) epidermal cell layers with a glucuronidase fusion protein construct provided evidence that the 15.4-kD protein encoded by HvS40 is localized to the nucleus. Expression of the gene is induced by jasmonate and salicylic acid; both are known to act as signaling compounds during senescence and defense toward pathogens. Transcript levels of HvS40 were observed to be particularly high in leaf sectors that undergo necrosis and chlorosis after infection with Pyrenophora teres. This pathogen-related expression is, in contrast, clearly reduced in transgenic barley plants expressing a stilbene synthase from grape (Vitis vinifera), whereas the mRNA level of a gene encoding the pathogen-related protein HvPR1 is unaffected. In situ hybridization with HvS40 antisense RNA revealed that during leaf senescence, the HvS40 transcript predominantly accumulates in the mesophyll. Taken together, the findings suggest a connection between the nuclear protein encoded by HvS40 and the degeneration of chloroplasts occurring during senescence and during infection of barley wild-type plants with P. teres.

Cloning of the murine TROP2 gene: conservation of a PIP2-binding sequence in the cytoplasmic domain of TROP-2

Trop-2 is a novel calcium signal transducer expressed at high levels by most human carcinomas. To develop an animal model to study the function of this molecule in vivo, we have cloned the murine Trop2 gene. Using human TROP2 primers, we amplified by PCR a segment of murine Trop2. This was used as a probe to clone a full-length gene by hybridization of a genomic library. The cloned murine Trop2 gene is functional, as indicated by sequencing and by expression after transfection. The murine Trop2 is 87.4% similar to its human homologue, with the highest conservation in the extracellular region between residues 86 and 157. Essentially all cysteines are conserved between the human and the murine genes, suggesting conservation of the Trop2 disulfide bridges and of its overall structure. Intriguingly, the cytoplasmic tail of Trop2 shows a highly conserved phosphatidylinositol 4,5-bisphosphate (PIP2)-binding sequence, which overlaps with a protein kinase C phosphorylation site. Thus, we speculate that PIP2 might regulate the phosphorylation state of Trop2 and play a role in its signal transduction. Murine Trop2 mRNA is detected in normal kidney, lung, ovary and testis, similarly to the human gene. Interestingly, the highest levels of expression are found in immortalized keratinocytes. Since Trop2 is undetectable in undifferentiated spindle cell carcinomas, this suggests a preferential expression at early stages of tumor progression.

Cloning of the gene encoding Trop-2, a cell-surface glycoprotein expressed by human carcinomas

We have cloned by expression the cDNA encoding Trop-2, a cell-surface glycoprotein expressed by most human carcinomas. Formal proof of the identity of the clone is the hybridization to DNA and RNA from genomic TROP2 transfectants. TROP2 is a single-copy gene in human cells, hybridizes to a single 1.8-kb mRNA from expressing sources and encodes a 35,709 Da type-1 transmembrane protein with a single transmembrane domain. TROP2 is essentially identical to GA733-1. Thus, we have proven that GA733-1, for which a protein product had not been identified, is a functional gene. TROP2 is also homologous to TROP1/KSA/GA733-2, confirming the serological similarities between the 2 molecules. The homology between the Trop-1 and Trop-2 peptides is clustered in 2 extracytoplasmic domains and in the transmembrane/cytoplasmic region. Twelve cysteines and a potential cytoplasmic tyrosine phosphorylation site are also conserved. Trop-1 and Trop-2 are homologous to serum IGF-II-binding proteins and appear as signal transducers. Thus, they likely represent novel cell-surface receptors and may play a role in regulating the growth of carcinoma cells. On the other hand, we have found no evidence for a role of Trop-2 and Trop-1 as homophilic adhesion molecules.

DNA methylation prevents the amplification of TROP1, a tumor-associated cell surface antigen gene

We tested the hypothesis that different genes can have different abilities to be amplified after transfection under comparable selection conditions. DNA from human lymphoid or choriocarcinoma cell lines was transfected into L cells. Transfectants for CD5, CD8A, TROP1, and TROP2, genes expressed on lymphocytes or trophoblast and carcinomas, were selected by fluorescence-activated cell sorting. To select for amplification of the transfected gene we cloned twice by fluorescence-activated cell sorting the transfectants with the highest expression. We analyzed a total of 38 families (1768 clones) derived from the original transfectants. We then analyzed by Southern blotting the clones with the highest increase in surface expression and determined the copy number of each transfected gene. CD5, CD8A, and TROP2 were amplified with high frequency and progressively, whereas TROP1 essentially was not amplified at all. We examined the hypothesis that DNA methylation prevents the amplification of the TROP1 gene by treating JAR choriocarcinoma cells with 5-azacytidine to decrease DNA methylation. DNA extracted at different times after the treatment was used for transfection. When DNA that showed demethylation of the TROP1 gene was used, 16 Trop-1 transfectants were obtained and 6 of them were found to contain up to 40 copies of the TROP1 gene per haploid genome. Thus, we showed that transfectants obtained from a demethylated TROP1 gene were amplified efficiently and progressively. We propose that DNA methylation affects DNA amplification either by altering the recognition of methylated DNA sequences or by changing the conformation of the chromatin of methylated segments. We speculate that DNA methylation is a determinant of gene amplification in vivo, for example in tumor cells.

Polybrene/DMSO-assisted gene transfer. Generating stable transfectants with nanogram amounts of DNA

Polybrene/DMSO-assisted gene transfer is a simple and versatile transfection strategy capable of producing high numbers of stable transfectants from adherent monolayer cultures with low (nanogram) quantities of exogenous DNA. The procedure involves two stages: adsorption and internalization. The former is mediated by polybrene (a polycation polymer) and favors the uniform coating of target cells with polybrene-DNA complexes. Following adsorption, the cells are permeabilized by a brief exposure to dimethyl sulfoxide (DMSO) to facilitate the uptake of DNA complexes. Diverse cell types can be exposed to a wide range of polybrene concentrations without adverse effects. By contrast, the key determinant of success is the DMSO permeabilization regime, which must be configured independently for each cell line. Protocols optimized for gene transfer in murine and human fibroblasts are presented along with a guide for the rapid optimization of the method. The advantages and limitations of the method are also discussed.

Biochemical characterization of Trop-2, a cell surface molecule expressed by human carcinomas: formal proof that the monoclonal antibodies T16 and MOv-16 recognize Trop-2

Trop-2 is a cell surface structure recognized by the 162-46.2 mAb and expressed by most human carcinomas. Since the 162-46.2 mAb works poorly in immunoprecipitation, to characterize the structure of Trop-2 we searched for other mAbs directed against this molecule. Selection of candidates was performed by analyzing the characteristics of mAbs directed against epithelial cells and by comparing the staining pattern of each mAb with the one of the 162-46.2 on frozen sections of human epidermis. Two mAbs, T16 and MOv-16, were selected for further analysis. Formal proof that candidate mAbs reacted with Trop-2 was obtained by comparing their binding patterns to mouse L cells transfected with the Trop-2 gene by genomic DNA transfection and selected by FACS using the FITC-162-46.2 mAb. In immunofluorescence FACS analysis the FITC-T16 and FITC-MOv-16 mAbs specifically stained Trop-2 transfectants. The specificity of binding was confirmed by selective blocking of the staining by the respective unconjugated mAb. Interestingly, cross-blocking studies indicated that the 162-46.2, T16 and MOv-16 mAbs recognize the same epitope or closely spaced ones on the Trop-2 molecule. T16 and MOv-16 efficiently immunoprecipitate Trop-2 from Trop-2 transfectants and from the human cell line OVCA-432, indicating that it is a cell surface glycoprotein, with an apparent molecular weight of 57 kD in non-reducing conditions. A weaker band of 38 kD is often co-precipitated with the 57 kD form in an apparently specific manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneous susceptibility of human melanoma clones to monocyte cytotoxicity: Role of ICAM-1 defined by antibody blocking and gene transfer

Five clones derived from the same human malignant melanoma lesion were studied for their susceptibility to killing by human monocytes activated by exposure to interferon (IFN)-gamma and lipopolysaccharide. Melanoma clones were heterogeneous in their susceptibility to human monocyte cytotoxicity, with one clone (2/21) exhibiting extremely low levels of lysis. The different levels of susceptibility to monocyte cytotoxicity were not accounted for by susceptibility or resistance to monokines [tumor necrosis factor (TNF), interleukin (IL)-1 and IL-6] because: (a) these effector molecules had little (TNF) or no (IL-1 and IL-6) cytolytic activity under these conditions; and (b) anti-TNF antibodies had marginal effects on cytotoxicity. Monocytes bound less to resistant than to susceptible melanoma cells. Monocyte-resistant 2/21 melanoma cells expressed substantially lower levels of ICAM-1 and VLA-4 than susceptible cells. Anti-CD18 and, to a lesser extent, anti-ICAM-1 mAb inhibited binding and cytotoxicity of human monocytes on malignant melanoma whereas anti-VLA-4 had no inhibitory action. Transfection of the ICAM-1 gene under the control of a constitutive promotor resulted in high levels of expression of ICAM-1 in 2/21 melanoma cells and, concomitantly, in augmented susceptibility to activated monocyte cytotoxicity. The augmented killing of ICAM-1 transfected 2/21 cells was inhibited by anti-ICAM-1 mAb. These results demonstrate that the CD18-ICAM-1 adhesion pathway can play an important role in the expression of human monocyte cytotoxicity on melanoma target cells and that heterogeneity in expression of ICAM-1 can underlie differences in susceptibility to tumoricidal activity.

Molecular cloning, reconstruction and expression of the gene encoding the alpha-chain of the bovine CD8--definition of three peptide regions conserved across species

We report the cloning of a cDNA encoding the alpha-chain of the bovine CD8 (BoCD8 alpha). A bovine thymus cDNA library was hybridized at low stringency with a human CD8 alpha cDNA clone. The first round of screening of 5 x 10(4) independent colonies yielded 12 clones containing incomplete BoCD8 alpha genes. Two further rounds of colony hybridization were conducted, each using as a probe the 5' fragment from the longest BoCD8 alpha clone previously isolated. The final screening yielded a clone containing a 2 kilobase (kb) insert. We mapped and sequenced the 2 kb BoCD8 alpha clone and compared it with the published sequences of the genes encoding the human, mouse and rat CD8 alpha. Sequence analysis confirmed that the clone under study encoded the BoCD8 alpha. The overall similarity of the BoCD8 alpha coding region with the human CD8 alpha coding sequence is 74.7% at the nucleotide level and 62.1% at the protein level. Lower levels of similarity are found with the mouse and rat CD8 alpha. Interestingly, three separate highly homologous regions are clearly defined at the peptide level in bovine versus human and mouse versus rat comparisons. Two of the regions are highly conserved among all species analysed, while the most 5' region is not. We speculate that the latter region may contain the binding site of CD8 alpha to the alpha 3 domain of major histocompatibility complex (MHC) class I molecules. Sequence analysis showed that the 2 kb BoCD8 alpha clone contains an incomplete coding region, i.e. lacks six bases corresponding to the first two amino acids of the leader region. To allow efficient translation and processing of the BoCD8 alpha gene, we constructed a chimeric gene containing the coding sequence of the BoCD8 alpha clone and synthetic sequences corresponding to the first two amino acids of the human CD8 alpha leader sequence. The chimeric gene was subcloned in the pKSV10 expression vector. The pKSV10-BoCD8 alpha construct is efficiently expressed both transiently in COS cells and stably in L cells, as determined by Northern blot and by FACS analysis, using the ILA-51 monoclonal antibody to BoCD8 alpha. The latter result formally proves that the ILA-51 antibody does indeed recognize the product of the BoCD8 alpha gene, as previously suggested on serological grounds.

A single-step DNA extraction procedure for the detection of serum hepatitis B virus sequences by the polymerase chain reaction

A rapid single-step procedure for the isolation of low molecular weight DNA using guanidinium thiocyanate and phenol as protein denaturants is described and applied for the detection of specific hepatitis B virus (HBV) DNA sequences from serum samples by the polymerase chain reaction (PCR). The novel technique is efficient and, when compared to the standard proteinase K/phenol/chloroform method has the advantage of being faster and easily adaptable to the routine processing of a high number of clinical samples by PCR and spot hybridization techniques.