P16 as a marker to differentiate atypical lipomatous tumor/well-differentiated liposarcoma from deep seated lipoma: An immunohistochemical analysis of 51 cases

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Background: Atypical lipomatous tumor (ALT)/well-differentiated (WD) liposarcoma is a locally aggressive malignant mesenchymal neoplasm characterized by supernumerary ring and giant marker chromosomes with amplification of MDM2 gene. These cytogenetic characteristics can be very helpful to distinguish ALT from deep-seated lipomas. As ALTs have only rare presence of lipoblasts, they can resemble benign lipomas rendering difficulty in morphological diagnosis. P16INK4 is a specific inhibitor of CDK4/CDK6. CDK6 gene is often found co-amplified with MDM2 gene in ALTs. P16 overexpression is a hallmark of cervical dysplasia. Our study investigates the value of p16 expression in cytogenetically confirmed ALTs and deep-seated lipomas. Design: Fifty-one (51) cases of lipomatous neoplasms, with cytogenetic results, from forty-three (43) patients were collected for the study from the archives in department of pathology, UMDNJ/NJMS during 1998 - 2005. These include 18 cases of deep-seated lipoma, one hibernoma, and 32 cases of ALT / well-differentiated liposarcoma (24 patients, five patients with recurrence, and four cases with de-differentiation). Immunohistochemical staining for p16 was performed on representative paraffin blocks. Staining results were scored according to intensity (negative 0, weak 1+, intermediate 2+, and strong 3+) and percentage of positive cells. Results: Twenty-eight cases (28/32, 87.5%) of ALT/WD liposarcoma, including all four cases of dedifferentiated liposarcoma, showed strong nuclear p16 expression. In cases of recurrence, the primary and recurrent tumor showed the same pattern of p16 staining. Four cases (4/32, 12.5%) of ALT/WD liposarcoma showed negative p16 expression. All cases of deep-seated lipoma (18/18, 100%) and single hibernoma showed negative p16 staining except focal positivity in areas of fat necrosis in two cases (p16 positivity, 87.5 vs. 0%, P <0.00001, Fisher's exact test). Conclusion: 1). P16 appears to be a valuable marker to differentiate ALT and deep-seated lipomas. 2). P16 expression remains unchanged in progression and transformation of ALT. 3). P16 related signal transduction pathway most likely is an early event in tumorogenesis of ALT.

No significant financial relationships to disclose.

Alveolar soft part sarcoma--reciprocal translocation between chromosome 17q25 and Xp11. Report of a case with metastases at presentation and review of the literature

The molecular pathogenesis of alveolar soft part sarcoma, a rare tumor with uncertain histogenesis, was elucidated recently and was shown to be due to a translocation between chromosome 17q25 and Xp11 resulting in a fusion product between TFE3 (a transcription factor gene) at chromosome Xp11 and a novel gene designated as ASPL at chromosome 17q25. This results in the transcriptional dysregulation in the pathogenesis of this neoplasm. Of the 12 cases reported so far, the translocation was due to non-reciprocal translocation in 11 cases with only one case demonstrating a reciprocal translocation with respective fusion products. We report yet another case with reciprocal translocation between chromosomes 17q25 and Xp11 with TFE3/ASPL fusion product who presented with metastatic disease. A standard cytogenetic analysis of primary tumor cells with G-banding revealed an abnormal karyotype: 46, X, t(X;17)(p11;q25)[15]/46,XX[5]. PCR analysis of the frozen tumor tissue revealed a type 1 fusion product as described in the literature. We demonstrate a rare cytogenetic abnormality in ASPS, namely reciprocal translocation between chromosomes 17q25 and Xp11 with demonstration of molecular fusion product between TFE3 and ASPL in a patient who initially presented with pulmonary metastases.

Age dependent aneuploidy and telomere length of the human vascular endothelium

RATIONALE

Aneuploidy and telomere length are two major parameters that have been associated with cellular senescence in vitro. In order to explore the role of aneuploidy and telomere length in aging of the human vasculature, we studied these two parameters in direct preparations of endothelial cells of the human abdominal aorta.

METHODS

Using fluorescent in situ hybridization on 'touch prep' slides, we evaluated aneuploidy of two autosomes (chromosomes 6 and 16) and sex chromosomes in non cultured endothelial cells of the abdominal aorta as a function of the donor's age.

RESULTS

We found that the frequency of aneuploidy of vascular endothelial cells significantly increased with age. This was expressed by age-dependent tetrasomy (r(s)=0.56, P=0.006 for chromosome 6; and r(s)=0.54, P=0.008 for chromosome 16), and age dependent loss of the Y chromosome (r(s)=0.85, P=0.0003). In addition, we found that telomere length was inversely correlated with age (r=-0.38, P=0.008). DATA INTERPRETATION: These findings suggest that indicators of cellular senescence, earlier observed in vitro, are also expressed in the human vascular endothelium in vivo. Aneuploidy and telomere attrition might thus play a role in the aging of the human vasculature.

Sex chromosome mosaicism in gonads of a fetus with cystic hygroma and deletion of the short arm of Y chromosome including loss of SRY

The SRY gene on the short arm of the Y chromosome is necessary for male development. Without SRY, patients with 46,XY karyotype develop as females, fail to achieve normal puberty and have dysgenic gonads and a high incidence of gonadoblastoma. Here we report a female fetus, aborted at 17 weeks of pregnancy, with a non-mosaic 46,X,del(Y)(p11.2).ish del(Y)(SRY-) karyotype diagnosed by classical cytogenetics and fluorescence in situ hybridization (FISH). Ovarian tissue was full of oocytes and mitotic figures. FISH studies of ovarian tissues with X and Y centromere probes revealed extensive sex chromosome mosaicism, manifested by loss of the Y chromosome and polysomy of the X chromosome. We propose that X chromosome polysomy is a post-zygotic event that arises to facilitate gonadal differentiation in the absence of all factors necessary for normal gonadal development.

Loss of chromosome 13 in cultured human vascular endothelial cells

In the vascular endothelium of human beings, telomere length is negatively related while the frequency of aneuploidy is positively related to donor age. Both in culture and in vivo the frequency of aneuploidy increases as telomere length is shortened. In this study we explored the relation between telomere length and aneuploidy in cultured human umbilical vein endothelial cells (HUVEC) by: (a) karyotype analysis and fluorescent in situ hybridization (FISH), (b) measurement of the terminal restriction fragments (TRF), and (c) assessment of replicative senescence by the expression of beta-galactosidase. Of 8 HUVEC strains, 7 cell strains lost chromosome 13, as shown by metaphase analysis and FISH of interphase cells. Five strains gained chromosome 11. In addition, five HUVEC strains became hypotetraploid shortly after the loss of chromosome 13. The loss of chromosome 13 was observed as early as PD 20, when mean TRF length was greater than 9 kb and the percentage of cells positive for beta-galactosidase was relatively low. The almost uniform loss of chromosome 13 suggests that this unique type of aneuploidy of HUVEC is the result of a progressive expression of clones with survival advantage.

Telomere attrition of the human abdominal aorta: relationships with age and atherosclerosis

Little is known about the turnover rate (i.e. the rate of replication and death) of cells in the intima and media of human arteries as a function of age and atherosclerosis. One indicator of the replicative history of cells is telomere length. In this work we explored the rate of telomere attrition as a function of age and atherosclerosis in cells of the human abdominal aorta. Telomere length, measured by the terminal restriction fragment using Southern analysis, was determined in the intima and media of the distal (infrarenal) versus proximal (suprarenal) segments of the abdominal aorta. Telomere length was then correlated with age and atherosclerotic grade. The rate of age-dependent telomere attrition was higher in both the intima and media of the distal versus proximal abdominal aorta. In addition, telomere length was negatively correlated with atherosclerotic grade. However, after adjustment for age, this relationship was not statistically significant. The high rate of age-dependent telomere attrition in the distal abdominal aorta probably reflects enhanced cellular turnover rate due to local factors such as an increase in shear wall stress in this vascular segment.

Telomeres and essential hypertension

The dynamics of telomere attrition in human beings might shape the course of age-dependent, complex genetic traits. One of these traits is essential hypertension. Age-dependent telomere attrition could lead to critically shortened telomeres and aneuploidy (ie, the loss or gain of chromosomes) with a resultant mosaicism that will be variably expressed in different cells and tissues. The chromosomal instability and loss of heterozygosity resulting from this process would promote an age-dependent expression of variant genes that harbor susceptibility for essential hypertension or genes that accelerate the process of aging.

Telomeres, hidden mosaicism, loss of heterozygosity, and complex genetic traits

Telomeres appear to function as an endogenous timing mechanism in human beings. Telomere attrition not only provides a satisfactory explanation for some aspects of aging, it might also resolve enigmatic features of complex genetic traits that are age-dependent. If, with the passage of time, telomere attrition in human beings leads to genomic instability and particularly the loss of chromosomes, then the age dependency of phenotypic expressions of complex genetic traits might result from the temporal loss of heterozygosity and the consequent expression of disease-causing genes. In this way, telomere attrition might play a role not only in aging, but also in the diverse expression of complex genetic traits, such as essential hypertension, non-insulin-dependent diabetes mellitus, atherosclerosis, and cancer.

Synchrony in telomere length of the human fetus

Telomere length, measured by terminal restriction fragments, was examined in tissues from human fetuses of gestational ages estimated as 15-19 weeks. The length of telomeres was similar in most fetal tissues. However, there were significant variations in telomere length among fetuses, with no apparent relationship between gestational age and telomere length. We conclude that synchrony in telomere length exists among tissues of the human fetus. This synchrony is apparently lost during extrauterine life.

Shortened telomere length in white blood cells of patients with IDDM

IDDM is a polygenic and autoimmune disorder in which subsets of white blood cells (WBCs) are engaged in the destruction of beta-cells of the pancreas. The mechanisms that account for the abnormal behavior of these cells in IDDM are not fully understood. By measuring the mean length of telomeres of WBCs from patients with IDDM, we tested the concept that telomeres might play a role in IDDM. We examined the lengths of the terminal restriction fragments (TRFs) of DNA of WBCs from 234 white men comprising 54 patients with IDDM, 74 patients with NIDDM, and 106 control subjects. When adjusted for age, the TRF length from WBCs of patients with IDDM was significantly shorter than that of nondiabetic control subjects (mean +/- SE: 8.6 +/- 0.1 vs. 9.2 +/- 0.1, P = 0.002). No significant difference was observed between the TRF length from WBCs of patients with NIDDM versus nondiabetic subjects. Neither the duration nor the complications of IDDM (i.e., nephropathy and hypertension) had an effect on the TRF length of WBCs from patients with IDDM. The shortened TRF length of WBCs of patients with IDDM likely reflects a marked reduction in the TRF length of subsets of WBCs that play a role in the pathogenesis of IDDM.

Interstitial insertion of Y-specific DNA sequences including SRY into chromosome 4 in a 45,X male child

A 45,X chromosome complement was found in the lymphocytes and skin fibroblast cultures of a male infant with minor facial anomalies and gastrointestinal abnormalities. Fluorescence in situ hybridization (FISH) studies with DNA probes specific for the entire Y chromosome (painting) and SRY identified insertion of a short piece of Y chromosome DNA, including the SRY region, into a der(4) chromosome at 4p15. FISH studies with DNA probes specific for Wolf-Hirschhorn syndrome (WHS) and telomere of 4p indicated that these 2 regions were intact and that the insertion of Y DNA had occurred proximal to the WHS region. High-resolution chromosome analysis performed after FISH studies showed an altered banding pattern of 4p at the region of insertion. The typical Giemsa dark band of 4p15 was consistently replaced by a gray band; this probably indicates deletion of the distal part of 4p15. The consequences of the double-chromosome anomaly in this patient were discussed in relation to his phenotype.

Familial transmission of a deletion of chromosome 21 derived from a translocation between chromosome 21 and an inverted chromosome 22

Chromosome analysis of a newborn boy with Down syndrome resulted in the identification of a family with an unusual derivative chromosome 22. The child has 46 chromosomes, including two chromosomes 21, one normal chromosome 22, and a derivative chromosome 22. Giemsa banding and fluorescent in situ hybridization (FISH) studies show that the derivative chromosome is chromosome 22 with evidence of both paracentric and pericentric inversions, joined to the long arm of chromosome 21 from 21q21.2 to qter. The rearrangement results in partial trisomy 21 extending from 21q21.2 to 21q terminus in the patient. The child's mother, brother, maternal aunt, and maternal grandmother are all carriers of the derivative chromosome. All have 45 chromosomes, with one normal chromosome 21, one normal chromosome 22, and the derivative chromosome 22. The rearrangement results in the absence of the short arm, the centromere, and the proximal long arm of chromosome 21 (del 21pter-21q21.2) in carriers. Carriers of the derivative chromosome in this family have normal physical appearance, mild learning disabilities and poor social adjustment.

Reflections on telomeres, growth, aging, and essential hypertension

Here we review the "telomere hypothesis of cellular aging." We propose that this hypothesis is relevant to our understanding of the roles of genetics as well as growth and development in the etiology of essential hypertension and its cardiovascular complications. Elements of this hypothesis and the speculations that we make can be directly tested using tissues (cells) obtained from human beings.

Uniparental disomy explains the occurrence of the Angelman or Prader-Willi syndrome in patients with an additional small inv dup(15) chromosome

A patient with Angelman syndrome and a 46,XY/47,XY,+inv dup(15)(pter-->q11: q11-->pter) karyotype and a patient with Prader-Willi syndrome and a 46,XY/47,XY,+inv dup(15)(pter-->q12: q12-->pter) karyotype were investigated with molecular markers along chromosome 15. Paternal uniparental isodisomy was found for all informative markers in the first case which indicates that this, rather than the presence of the extra chromosome, is the cause of the Angelman syndrome phenotype. Similarly, the PWS patient showed maternal uniparental distomy with absence of PWS region material on the inv dup(15) chromosome. If (1) marker chromosomes are an occasional by product of 'rescuing' a trisomic fertilisation, or (2) if duplication of the normal homologue in a zygote which has inherited a marker in place of the normal corresponding chromosome 'rescues' an aneuploid fertilisation, or (3) if the presence or formation of a marker chromosome increases the probability of non-disjunction, then uniparental disomy might be found occasionally in other subjects with de novo marker chromosomes.

Partial trisomy 11q in a female infant with Robin sequence and congenital heart disease

We describe the clinical and cytogenetic findings in a female infant with partial trisomy 11q, Robin sequence, cardiac anomalies, and other minor malformations. We compare the phenotypic similarities of our case to a series by Pihko et al. (1981), who reported on 20 cases with partial trisomy 11q with similar associated craniofacial and cardiac defects. We conclude that genetic etiologies for patients diagnosed with the Robin sequence may be more common than previously believed and that initial karyotyping should be performed to aid both diagnosis and clinical management. In addition, the pattern of Robin sequence and cardiac defects may be specifically suggestive of partial trisomy 11q.

High-level expression of enzymatically active human Cu/Zn superoxide dismutase in Escherichia coli

Expression of human Cu/Zn superoxide dismutase (SOD) with activity comparable to the human erythrocyte enzyme was achieved in Escherichia coli by using a vector containing a thermoinducible lambda PL promoter and a beta-lactamase-derived ribosomal binding site. The recombinant human SOD was found in the cytosol of disrupted bacteria and represented greater than 10% of the total bacterial protein. The enzyme was purified to homogeneity by salt precipitation, gel filtration chromatography, and ion exchange chromatography. The active enzyme was obtained in high yield only when 1 mol of copper and 1 mol of zinc were incorporated into each mol of subunit during bacterial growth or by reconstitution of the apoenzyme. Human Cu/Zn SOD produced in bacteria has an apparent subunit molecular mass of 19 kDa on NaDodSO4/polyacrylamide gels. The native enzyme behaves as a dimer of 32 kDa as determined by gel filtration. Sequence analysis of the NH2 terminus revealed that the first 14 amino acids corresponded to authentic human SOD except that the NH2-terminal alanine was not acetylated. Thus, the bacterial processing system readily removes the NH2-terminal methionine residue from recombinant human SOD.

Inhibition of lactogenic activities of ovine prolactin and human growth hormone (hGH) by a novel form of a modified recombinant hGH

A recombinant analog of human GH (hGH) lacking 13 amino acids at the amino-terminus (Met14hGH) inhibited the hGH- or ovine PRL (oPRL)-stimulated proliferation of Nb2 lymphoma cells and bovine PRL-stimulated fat synthesis and alpha-lactalbumin secretion in explants from bovine lactating mammary gland. The inhibition was competitive in nature, and in Nb2 cells could be abolished by an excess of hGH or oPRL. Inhibition of oPRL-stimulated proliferation of Nb2 cells by Met14hGH could also be specifically abolished by anti-hGH monoclonal antibodies. Met14hGH had no growth-stimulating activity in Nb2 cells and was not cytotoxic. It also did not affect glucose uptake by the mammary gland explants. Met14hGH competed with [125I]hGH for binding to intact Nb2 cells, IM-9 lymphocytes, solubilized microsomal fraction from lactating bovine mammary gland, and microsomal fraction from the liver of female virgin rats, but its affinity for those receptors was 2 orders of magnitude lower than the affinity of hGH. Since Met14hGH used in most experiments contained about 25% impurities and degradation products, a small amount of it was further purified by immunoaffinity chromatography. Two purified fractions, one consisting of a single 20K protein and the other accompanied by a small amount of 25K protein, were obtained. Both fractions exhibited increased inhibition of hGH- or oPRL-stimulated proliferation of Nb2 cells, thus indicating that the inhibitory activity results from the intact Met14hGH molecule. To the best of our knowledge, this is the first report describing the inhibition of lactogenic hormone activities by a modified hGH.

Preferential transcription and nuclear transport of globin gene sequences, as control steps leading to final differentiation of murine erythroleukemic cells

Murine erythroleukemic (MEL) cells undergo a specific program of differentation in vitro, which is mainly characterized by accumulation of globin mRNA. These cells serve as a model system to study in detail the expression of a specific gene product at the transcriptional and post-transcriptional level. In this report we describe experiments in which the transcription rate of globin and non-globin genes, as well as their cytoplasmic appearance, was measured during the differentiation process. Two independent steps for regulating the abundance of globin mRNA were observed. On the transcriptional level we have observed that, in contrast to the transcription of globin genes, the transcription rate of non-globin genes is dramatically reduced throughout the period of induction. When the rate of cytoplasmic appearance was measured newly synthesized globin RNA molecules were found to be preferentially transported into the cytoplasm. It was shown that the reduction in cytoplasmic appearance of nonglobin genes is not a result of a shut-off in their transcriptional activity. In cells treated with 12-O-tetradecanoylphorbol 13-acetate the transcription rate remains constant while a continuous reduction in the cytoplasmic appearance is observed. These two independent phenomena which affect the non-globin genes, i.e. the suppression of their transcription and reduced cytoplasmic appearance, lead to the reduction in the relative amounts of the stable poly(A)-rich mRNA population and to the accumulation of globin sequences in the cytoplasm of the differentiated erythroid cells. These observations are in agreement with our previous model, which claimed that disappearance of the stable poly(A)-rich mRNA population is an obligatory process leading to the final differentiation of MEL cells.

Evaluation of immunological methods for detection of bovine growth hormone (BGH) produced in E. coli

The use of several immunological methods for studies on synthesis of bovine growth hormone (BGH) by E. coli is described here. The ELISA procedure was shown to be the least sensitive and unfit for assaying BGH in E. coli extracts. The solid-phase radioimmunoassay (RIA) proved to be highly sensitive, but since E. coli extract itself (not containing BGH) interfered with the immunological reaction, its use for measuring BGH was practically limited. The best adequate procedure proved to be radioimmunoassay in solution, which was not adversely affected by the E. coli extract and was sufficiently sensitive to detect nanogram quantities of BGH. The size of the BGH produced by normal bacterial cells was investigated by protein fractionation, transfer to nitrocellulose paper and detection by anti-BGH serum. This method was also served for semi-quantitative determination of BGH in the bacterial extract.

Expression of a cloned bovine growth hormone gene in Escherichia coli minicells

The synthesis of polypeptides in Escherichia coli minicells, directed by a pBR322 plasmid and its derivative-carrying bovine growth hormone cDNA insert, was studied. Two polypeptides coded by the ampicillin-resistance (Apr) gene (32 000 and 28 000 daltons) and a tetracycline-resistance (Tcr) polypeptide (36 000 daltons) were identified by insertion inactivation. Two additional polypeptides of 37 000 and 34 000 daltons of as yet unknown function were detected in all extracts regardless of the presence of the Apr or Tcr genes in the plasmid. The pBR322-BGH recombinant plasmid coded for several novel polypeptides, among them one of 46 000 daltons, presumably a fused product of the BGH and beta-lactamase genes. This protein, however, was not secreted into the periplasmic space of the cells as was the beta-lactamase.

Screening for highly active plasmid promoters via fusion to beta-galactosidase gene

A plasmid containing promoter-deleted inactive beta-galactosidase gene [1] was used to select promoters of the pEP 121 plasmid [2]. Colonies of cells harboring reactivated beta-galactosidase gene were identified by their red color on McConkey plates. The quantitative amounts of beta-galactosidase produced in each clone were estimated by assaying enzyme activity and by measuring the specific beta-galactosidase protein following fractionation of total cells' proteins on polyacrylamide gel. A wide range of enzyme activities was observed. The most active promoter isolated was shown to promote beta-galactosidase production more efficiently, compared with the original beta-galactosidase promoter, amounting to 20% of all cell proteins. Such highly active promoters may be utilized in the future, to promote expression of cloned genes in bacteria.

Large globin RNA molecules and their processing

RNA containing beta-globin message sequences larger than 2000 nucleotides could be detected in nuclei of murine erythroid cells using cloned beta-globin cDNA. Under steady-state conditions, when nuclear RNA was separated on denaturing agarose gels and covalently bound to diazobenzyloxymethyl-paper, a 4200-nucleotide and a approximately equal to 3500-nucleotide band could be seen. The presence of these large molecules could also be visualized under the electron microscope after hybridization to a beta-globin genomic DNA fragment. We suggest that these molecules are precursors to mature mRNAs. In addition to these large molecules, a series of molecules smaller than 2000 nucleotides were seen. These are postulated to be processing intermediates in the maturation of beta-globin mRNA.

Modulation of globin gene expression by a tumor promoter during induced differentiation of Friend erythroleukemic cells

Friend erythroleukemic cells were induced to differentiate by dimethylsulfoxide (Me2SO) in the absence or presence of the tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate. The effects of the latter on the molecular parameters related to globin mRNA metabolism were examined. When differentiation was scored by benzidine staining, it had an inhibitory effect on Me2SO-treated cells. On the other hand, when differentiation was followed by determination of globin mRNA accumulation, it had a pleiotropic effect on Me2SO-treated cells. At the early phase of differentiation (2--3 days) the rate of globin mRNA accumulation was higher in the promoter-treated cells than in the control. This unexpectedly high level of accumulation was followed by a sharp reduction and most of the globin RNA sequences disappeared at later stages of differentiation (days 4--5). The reduction can be related to the effect of the promoter on the stability of globin RNA in the cytoplasm which was reduced from a half-life of 16 h to that of 8 h only. Other parameters, such as the rate of globin mRNA synthesis and its capability to serve as a template for cell-free protein synthesis were not affected by treatment with the promoter throughout the differentiation process.

Cloning of bovine growth hormone gene and its expression in bacteria

A hybrid plasmid was constructed containing beta-lactamase gene of plasmid pBR322 and cloned coding sequences of bovine growth hormone (BGH). The constructed plasmid contains all DNA sequences required to encode BGH, and when used as a hybridization probe it detects one growth hormone gene in the bovine genome. The cloned DNA sequences are inserted into the beta-lactamase gene in the correct reading frame for BGH synthesis. The hybrid gene is expressed in bacteria and the product, a fused beta-lactamase-bovine growth hormone protein, is specifically immunoprecipitated with anti-serum to BGH. Unlike beta-lactamase, very little growth hormone containing sequences can be detected in the periplasmic space.

Gentamicin bioautography assay vs. the microbiological disk test

The use of bioautography for quantitative measurement of gentamicin concentrations was compared with the disk test. Following chromatographic separation and bioautography, gentamicin produced inhibition zones, 2 approximately 7 times larger than the inhibition zones formed by the same amounts of gentamicin in the disk test. Bioautography, therefore, is a more sensitive assay method.

Isolation of viable deletion mutants of Streptomyces actinophage (Pal 6) and their molecular characterization

Deletion mutants of bacteriophage Pal 6 were isolated by successive treatments of either heat (60 degrees C) or pyrophosphate (10 mM). These mutants were characterized by restriction enzyme cleavage analysis. The pyrophosphate resistant clones lost the whole Eco R1 fragment in which the Sal I site is located, as well as an unrelated Hind III fragment. These results show that the region containing the Sal I site in the phage genome is not essential for phage viability. This single Sal I site is therefore suitable as a potential insertion site for DNA cloning. On the other hand, the heat resistant clones that were isolated and characterized do not appear to have detectable deletions as indicated by their Eco R1 DNA digestion pattern.

Radioimmunoassay of gentamicin in Micromonospora medium extracts

Medium extracts of Micromonospora adversely affected a radioimmunoassay which was used for the measurement of gentamicin in the medium. An overestmation or an underestimation resulted, as judged by the addition of extracts to a gentamicin standard sample.

Evaluation of several enrichment procedures for the isolation of recombinant plasmid DNA

A number of methods for the selective enrichment of recombinant plasmids were examined; these include alkaline phosphatase treatment of the restricted pBR322 vector, as well as a combination of this and S1 nuclease treatment of the ligated mixture of pBR322 and pCR1 plasmids or S. griseus DNA followed by D-cycloserine treatment to enrich for cells carrying recombinant molecules. The relative efficiencies of these methods were compared.

Methylation and capping of RNA polymerase II primary transcripts by HeLa nuclear homogenates

HeLa nuclear homogenates incubated in vitro incorporate [beta-32P]ATP and S-[methyl-3H]-adenosylmeth-ionine ([3H]SAM) into blocked methylated 5' termini of newly synthesized RNA. Approximately 10% of the RNA chains initiated in vitro with [beta-32P]ATP are subsequently blocked by condensation of GMP to di- or triphosphate terminated RNA. The blocked termini can then be methylated by transfer of methyl groups from [3H]SAM to the 7 position of the guanosine and 2'-O position of the adenosine to form m7Gpp*pAm- capped terminus. In addition to conventional triphosphate caps, HeLa nuclear homogenates produce capping structures containing two phosphate residues in the pyrophosphate bridge. The two distinct cap forms were separated by DEAE-cellulose chromatography and analyzed. In contrast to triphosphate caps (m7GpppXm) in which X can be any one of the four nucleosides (G, A, C, or U), in diphosphate caps (m7GppXm), more than 95% of the penultimate nucleoside Xm is G. Incorporation of both [beta-32P]ATP and [3H]SAM into caps was markedly reduced by low concentrations of alpha-amanitin. However, an ammonium sulfate fraction of the nuclear homogenate can cap beta-32P-labeled RNA (pp*pA-RNA) to form m7Gpp*pA-RNA, in the presence of 0.5 microgram/mL of alpha-amanitin. Therefore, the nuclear capping enzyme is resistant to this drug. Our results indicate that RNA polymerase II primary transcripts are the substrate for the cellular capping enzyme and that the beta phosphate in the pyrophosphate bridge (m7GgammapbetapalphapXm) is derived from the 5' ends of the RNA chains.

Initiation of RNA synthesis in isolated nuclei

Ribonucleotide triphosphates, labeled at the beta position, were synthesized and used directly to quantify RNA chain initiation in nuclei isolated from Friend cells grown in tissue culture. At the optimal salt concentration, low-molecular-weight RNAs (4-5 S) synthesized by RNA polymerase III were the predominant species initiated. Less than 5% of the molecules were initiated by polymerase II. We calculate that 50-80% of the small RNA molecules synthesized in vitro were also initiated in vitro. Assuming that a substantial fraction of the nuclei were active in vitro, the number of 4-5 S RNA molecules initiated per nucleus was about 100 molecules/min.

Globin RNA precursor molecules: biosynthesis and process in erythroid cells

Hybridization of labeled RNA with excess amounts of DNA complementary to globin mRNA, in conjunction with a pulse-chase technique, were used to investigate the biosynthetic pathway of globin mRNA in erythroid cells. Three species of molecules sharing common sequences with globin mRNA were detected in the nuclei of these cells, two of which are larger than the cytoplasmic globin mRNA. One species was approximately 7 times larger than globin mRNA ("27S"), and the other ("15S") was only about twice the size of cytoplasmic globin mRNA. The largest species lacked poly(A) sequences, while the others contained poly(A), After chase, the large RNA species gradually disappeared ( 1/2 = 5 min), while the cytoplasmic 10S species accumulated. From these results a model is proposed describing the biosynthetic pathway of globin RNA transcription: an early transcription product is the large molecule "27S" (approximately 5000 nucleotides long) which is then cleaved into a smaller species "15S" (approximately 1500 nucleotides). This intermediate precursor is then clipped, presumably at the 5' end, and finally converted to the exported "10S" molecule (approximately 750 nucleotides) which accumulates in the cytoplasm.

Biosynthesis and stability of globin mRNA in cultured erythroleukemic Friend cells

Biosynthesis and stability of the mRNA population in DMSO-induced Friend erythroleukemic cells were studied after labeling the RNA with 3H-uridine and then chasing it with nonlabeled uridine. Globin RNA metabolism was studied by hybridization to excess complementary DNA convalently coupled to oligo(dT)-cellulose. After a labeling period of 120 min, 2-4% of the poly(A)-containing labeled RNA was in globin RNA; it decayed with a half-life of 16-17 hr. The rest of the poly(A)-containing RNA was composed to two kinetic populations: 85-90% decayed with a half-life of about 3 hr, while 10% decayed with a half-life of about 37 hr. The portion of globin RNA in labeled poly(A)-containing RNA behaved in an unexpected fashion during the chase period. During the initial chase period, the percentage of globin RNA increased rapidly, reaching a maximum of about 15% at 20 hr, but it subsequently declined gradually. Based on these findings, a model was built that describes the changes in the proportion of globin mRNA in poly(A)-containing RNA during continuous synthesis and after chase of the labeled RNA. It appears that if the parameters described remain constant during the maturation of erythroblasts, then this model would not account for the almost exclusive presence of globin RNA in the reticulocyte. By far the most effective way to achieve this high level of globin RNA is the destabilization of the mRNA population which is more stable than globin RNA, and not the stabilization of globin RNA itself.

Quantitation of labeled globin messenger RNA by hybridization with excess complementary DNA covalently bound to cellulose

A method is described to quantitate labeled globin mRNA by hybridization with excess cDNA which was enzymatically polymerized on oligo(dT)-cellulose. In a large excess of cDNA-cellulose the rate of RNA hybridization was dependent on DNA concentration and not on RNA concentration. Nonhybridized RNA can be digested by RNase and washed from the cDNA which is covalently bound to cellulose. This enables the detection of labeled globin mRNA even when present in a porportion as low as 0.02-0.03% of the total RNA.

Preferential synthesis of viral late RNA by nuclei isolated from SV40 lytically infected cells

Nuclei from SV40-infected monkey cells were isolated late in lytic infection and their cell-free transcriptional activity was characterized. 3H-RNA synthesized in vitro was hybridized to excess quantities of separated SV40 DNA strands which were each covalently bound to Sepharose. It was found that 3-5% of the newly synthesized RNA is virus-specific and that the plus-strand DNA, coding for late RNA sequences, is transcribed at a rate about 15 times higher than that of the minus-strand DNA, which codes for early RNA sequences. This indicates that transcriptional control has a major role in determining the relative abundancy of early and late RNA classes in lytically infected cells.

Purification of SV-40 messenger RNA by hybridization to SV-40 DNA covalently bound to Sepharose

SV-40 DNA sheared form was coupled in a stable covalent bond to cyanogen bromide activated Sepharose. Under the conditions used at least 80% of the DNA was bound to Sepharose. The T 1/2 of hybridization of 0.5 mug/ml of SV-40 cRNA to SV-40 DNA-Sepharose was 1 hr. This rate of hybridization is sufficiently rapid to purify SV-40 sequences from solutions containing as little as 0.05-0.1 mug/ml. Nonspecific hybridization of RNA is in the range of 0.1-0.2% of the total input RNA. The DNA-Sepharose is fairly stable and can be reused several times to purify RNA. The SV-40 DNA-Sepharose was used to select large quantities of virus specific RNA from SV-40 infected BS-C-1 cells. The virus specific RNA when added to cell-free extracts from wheat germ was shown to direct the synthesis of the major viral structural protein VP-1.

Cell-free translation of messenger RNA of simian virus 40: synthesis of the major capsid protein

Extracts of wheat germ are capable of synthesizing the major capsid protein of simian virus 40. Poly(A)-containing RNA from BS-C-1 cells infected with simian virus 40 directed the synthesis of a novel polypeptide that migrates in polyacrylamide gels together with the major capsid polypeptide of simian virus 40, VP-1. The patterns of the major tryptic peptides of purified VP-1 and the novel polypeptide synthesized in vitro were identical after two-dimensional paper electrophoresis. The novel polypeptide was not synthesized in response to poly(A)-rich RNA from uninfected cells or from virus-infected cells treated with cytosine arabinoside. Messenger RNA from infected cells purified by selective hybridization to DNA of simian virus 40 directs the synthesis of a major polypeptide of electrophoretic mobility similar to that of VP-1 of simian virus 40. This approach should prove useful in identifying additional products specified by DNA tumor viruses.

Translation of bacteriophage Q messenger RNA in a murine Krebs 2 ascites tumor cell-free system

Qbeta is a small bacterial virus whose three genes are encoded in a single-stranded molecule of RNA. This RNA serves directly as the Qbeta message. Here we describe conditions under which RNA corresponding to the coat cistron of this bacterial virus is translated in a system derived from mammalian cells. Translation of the bacterial virus messenger RNA is less effective than that of mammalian globin messenger RNA, but is somewhat enhanced by mild alkali treatment of the messenger. The synthesized product when subjected to electrophoresis migrates with authentic Qbeta coat protein and yields tryptic peptides that correspond to those derived from the Qbeta coat protein.