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R E Streeck

Publications and source records attributed to R E Streeck.

12 recordsLinked to original sources
PubMed1992

Deletion and insertion mutants of HBsAg particles.

We have found previously that hybrid 22-nm HBsAg particles can be created by insertion of short antigenic sequences into the HBV major envelope protein. We have now performed a detailed deletion mutagenesis of the S gene of HBV encoding HBsAg. Deletion of the 51 C-terminal amino acids including most of the third and all of the fourth hydrophobic domain of the S protein did not affect particle assembly and secretion. However, secretion of 22-nm particles was abolished by minor deletions in the N-terminal region. Insertion and deletion/substitution mutants carrying a poliovirus epitope at the N-terminus and the preS1 region at the C-terminus have been characterized.

DNA Mutational Analysis↗
PubMed1992

Human papillomavirus type 42: new sequences, conserved genome organization.

We report the nucleotide sequence and genome organization of the human papillomavirus type 42. HPV42 DNA was isolated from vulvar papillomas. It has been detected in benign forms of proliferative lesions only. The genome of HPV42 is 7917 bp long and shows the open reading frame pattern conserved in all HPVs sequenced so far. HPV42 has no high degree of sequence homology to any of the known HPVs. It shows characteristics previously found either exclusively in HPVs associated with invasive carcinomas or exclusively in nongenital HPVs. Therefore it cannot be readily ascribed to any of the established subgroups of human papillomaviruses.

Base Sequence↗
PubMed1990

Enhancement of gene expression by somatic hybridization with primary cells: high-level synthesis of the hepatitis B surface antigen in monkey Vero cells by fusion with primary hepatocytes.

Vero cells transfected with the S gene encoding the surface antigen (HBsAg) of the hepatitis B virus (HBV) synthesize HBsAg at low levels. We have obtained a large increase in S gene expression by somatic hybridization of Vero cells with primary hepatocytes, which are the natural target cells for HBV infection. Fusion with cells other than hepatocytes did not enhance expression of the S gene. The Vero/hepatocyte hybrid clones analyzed are stable and have maintained a high level of HBsAg synthesis over prolonged periods. Hybrid cell lines may be of general interest for the high-level synthesis of proteins using cloned genes.

Animals↗
PubMed1979

Patchwork structure of a bovine satellite DNA.

According to a previous restriction nuclease analysis, bovine 1.706 satellite DNA (density 1.706 g/cm3 in CsCl) is organized in an unusual structure of superimposed long- and short-range repeats (Streeck and Zachau, 1978). We have now determined the nucleotide sequence of this satellite DNA in both cloned fragments and fragments from the total satellite DNA. Each long-range repeat unit (about 2350 bp) is divided into four segments. Each segment consists of different variants of a basic 23 bp sequence which is itself composed of a dodecanucleotide and a related undecanucleotide. A total of 2400 nucleotides have been sequenced. Detailed analysis of the sequence divergence reveals that both the overall extent of divergence and the frequency of base changes at individual positions of the 23 bp repeats are characteristically different in the various segments. Preferentially methylated sites and a high incidence of symmetry elements are found. In two of the four segments, 22 of 23 bp of the prototype sequence are included in six overlapping elements of dyad symmetry and in a palindrome. A scheme for the evolution of the satellite DNA from a basic dodecanucleotide is proposed which is based on the different degrees of divergence for the various repeats superimposed in this satellite DNA.

Animals↗
PubMed1979

Physical map of PM2 DNA.

The cleavage sites of the restriction nucleases HpaI, HpaII, HindII, HindIII, and PstI have been mapped on the DNA of the bacteriophage PM2. This map has been used for the localization of two strong binding sites of Escherichia coli RNA polymerase on PM2 DNA.

Bacteriophages↗
PubMed1978

Closely spaced nucleosome cores in reconstituted histone.DNA complexes and histone-H1-depleted chromatin.

It has been demonstrated by digestion studies with micrococcal nuclease that reconstitution of complexes from DNA and a mixture of the four small calf thymus histones H2A, H2B, H3, and H4 leads to subunits closely spaced in a 137 +/- 7-nucleotide-pair register. Subunits isolated from the reconstituted complex contain nearly equimolar amounts of the four histones and sediment at 11.6S. On DNase I digestion both the reconstituted complex and the separated subunits gave rise to series of single-stranded DNA fragments with a 10-nucleotide periodicity. This indicates that the reconstitution leads to subunits very similar to nucleosome cores. Nucleosome cores closely spaced in a 140-nucleotide-pair register were also obtained upon removal of histone H1 from chromatin by dissociation with 0.63 M NaCl and subsequent ultracentrifugation. In reconstitution experiments with all five histones (including histone H1) our procedure did not lead to tandemly arranged nucleosomes containing about 200 nucleotide pairs of DNA. In the presence of EDTA, DNase II cleaved calf thymus nuclei and chromatin at about 200-nucleotide-pair intervals whereas in the presence of Mg2+ cleavage at intervals of approximately half this size was observed. The change in the nature of the cleavage pattern, however, was no longer found after removal of histone H1 from chromatin. This indicates that H1 influences the accessibility of DNase II cleavage sites in chromatin. This finding is discussed with respect to the influence of histone H1 on chromatin superstructure.

Animals↗
PubMed1975

Mapping of cleavage sites for restriction endonucleases in lambdadv plasmids.

Restriction nucleases from Escherichia coli carrying the resistance transfer factor RI, from Hemophilus influenzae, Hemophilus parainfluenzae, and Bacillus subtilis were used for the generation of specific DNA fragments from lambdadv plasmids. Cleavage maps were established for various plasmids containing different but overlapping parts of bacteriophage lambdaDNA by analysis of digestion patterns obtained in polyacrylamide gel electrophoresis. The correlation between the plasmid cleavage maps and the genetic map of lambda was based upon the location of the EcoRI cleavage site at 81.3% of lambda fractional length and the position of promoters PL and PR on the plasmid DNA fragments.

Bacillus subtilis↗
PubMed1975

Investigation of the repetitive sequences in calf DNA by cleavage with restriction nucleases.

Calf thymus DNA was digested with the restriction nucleases from Escherichia coli carrying resistance transfer factor I, Haemophilus influenzae Rd and Bacillus subtilis X5 (EcoRI, Hind II, and Bsu, respectively) and submitted to polyacrylamide gel electrophoresis. About 10% of the DNA migrated as discrete fragments in 8, 16, and 30 bands, respectively, superimposed upon a continuous distribution of various size DNA fragments. The fragments within the bands are repeated 2000 to 160000 times in the haploid genome. Their sizes range from about 10 to a few thousand nucleotide pairs. About 5% of the DNA in EcorRI and Hind II digests migrated in a band at the position of undigested DNA, probably due to the resistance of long stretches of DNA against these nucleases. Calf DNA fragments obtained with EcoRI and Hind II were isolated by preparative gel electrophoresis. DNA from the bands showed the behaviour of repetitive DNA in renaturation experiments. An EcoRI fragment 1300-nucleotide-pairs long, which represents 6% of the calf genome and occurs 130000 times, is tandemly repeated (derived from the satellite of 1.714 g/cm3, see below). Another EcoRI fragment of 970 nucleotide paris, which represents 0.5% of the calf genome and is derived from the DNA of 1.710 g/cm3 seems to be structurally related to the foregoing fragment since it shows a similar Hind II and Bsu cleavage pattern. It alternates with a 1550-nucleotide-pairs-long EcoRI fragment. In another series of experiments total calf DNA was separated into main-band and satellite fractions by density-gradient centrifugation and chromatography in the presence of a base-specific dye. Purified fractions were characterized by analytical ultracentrifugation and by Hind II and EcorRI digestions. From the cleavage patterns of purified fractions an assignment of the bands found with total calf DNA to satellite fractions was possible. Most fragments were derived from the components of density 1.709 and 1.710 g/cm3. The 1.714-g/cm3 satellite was cleaved into a 1300-nucleotide-pairs-ling EcorRI fragment and two Hind II fragments of 1100 and 180 nucleotide pairs. The satellites of 1.723 g/cm3 and 1.705 g/cm3 were not cleaved by either Hind II or EcoRI DNAase. On digestion of main band DNA with Bsu a 160-nucleotide-pairs-long fragment was obtained which was also observed, at a frequency of about 160000, in the Bsu digest of EcoRI fractions from total calf DNA.

Animals↗