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Biomedical subjects

W E Hahn

Publications and source records attributed to W E Hahn.

At least 37 records · Page 2Linked to original sources
PubMed1979

Complex population of nonpolyadenylated messenger RNA in mouse brain.

The complexity of nonadenylated mRNA [poly(A)-mRNA] has been determined by hybridization with single-copy DNA (scDNA) and cDNA. Our results show that poly(A)- and poly(A)+ mRNA are essentially nonoverlapping (nonhomologous) sequence populations of similar complexity. The sum of the complexities of poly(A)+ mRNA and poly(A)- mRNA is equal to that of total polysomal RNA or total mRNA, or the equivalent of approximately 1.7 x 10(5) different sequences 1.5 kb in length. Poly(A)- mRNA, isolated from polysomal RNA by benzoylated cellulose chromatography, hybridized with 3.6% of the scDNA, corresponding to a complexity of 7.8 x 10(4) different 1.5 kb sequences. The equivalent of only one adenosine tract of approximately 20 nucleotides per 100 poly(A)- mRNA molecules 1.5 kb in size was observed by hybridization with poly(U). cDNA was transcribed from poly(A)- mRNA using random oligonucleotides as primers. Only 1-2% of the single-copy fraction of this cDNA was hybridized using poly(A)+ mRNA as a driver. These results show that poly(A)- mRNA shares few sequences with poly(A)+ mRNA and thus constitutes a separate, complex class of messenger RNA. These measurements preclude the presence of a complex class of bimorphic mRNAs [that is, species present in both poly(A)+ and poly(A)- forms] in brain polysomes.

Animals↗
PubMed1978

Complex population of mRNA sequences in large polyadenylylated nuclear RNA molecules.

Polyadenylylated heterogeneous nuclear RNA [poly(A)-hnRNA] from mouse brain was subjected to electrophoresis in agarose gels containing CH3HgOH, and molecules larger than 8 kilobases or 13 kilobases were recovered. cDNA was then transcribed from polyadenylylated RNA fragments cleaved from these large molecules. The resulting cDNA hybridized almost to completion with poly(A)-mRNA isolated from mouse brain polysomes. From the hybridization kinetics of this cDNA with its template RNA, it was estimated that the sequence complexity of the 3'-proximal sequences (of the same average size as mRNA) of the greater than 8 kilobase poly(A)-hnRNA was about 57,000 kilobases. The sequence complexity of poly(A)-mRNA, estimated from the template-driven hybridization kinetics of its respective cDNA, was about 110,000 kilobases. It is concluded that most, if not all, of the 3'-proximal sequences of large poly(A)-hnRNA molecules are homologous with mRNA in the mouse brain and that at least 40,000 different mRNA sequences (or portions of mRNA sequences) are represented in the 3'-proximal sequences of greater than 8 kilobase poly(A)-hnRNA.

Animals↗
PubMed1978

Assay of DNA-RNA hybrids by S1 nuclease digestion and adsorption to DEAE-cellulose filters.

A fast and accurate assay procedure for DNA-RNA hybrids is described in which exhaustive digestion of unhybridized DNA with S1 nuclease is followed by binding of hybrids to filter discs of DEAE-cellulose. The digested DNA can be efficiently washed from the filters so that background levels of 0.1-0.2% of input tracer DNA can be achieved, in contrast to the much higher (approximately 1-5%) backgrounds obtained using TCA precipitation procedures. Short duplexes, as small as 36 nucleotides in length, which are inefficiently bound to hydroxyapatite, are quantitatively bound to the DEAE-cellulose filters.

Animals↗
PubMed1977

One strand equivalent of the Escherichia coli genome is transcribed: complexity and abundance classes of mRNA.

DNA-RNA hybridization experiments show that essentially all of the genomic information is transcribed. High, intermediate, and rare abundance classes of messenger RNA (mRNA) are present, and their estimated complexities are equal to about 240, 1300, and 700 average-sized mRNA species, respectively. The high abundance mRNA species are present, an average, two to three copies per cell and constitute about 95 percent of the mRNA mass. Intermediate abundance mRNA species are present, on average, about once per 35 cells. The relative abundance and complexity of these mRNA classes correspond well with previous respective measurements on protein. Rare RNA species are thought to represent maximally repressed genes. Analysis of RNA synthesized in vitro by isolated nucleoids (chromosomes) suggests that sense and nonsense sequences are extensively interspersed on a given strand of the DNA.

Chromosome Mapping↗
PubMed1977

Removal of RNase activity from DNase by affinity chromatography on agarose coupled aminophenylphosphoryl-uridine-2' (3')-phosphate.

Severe degradation of high molecular weight RNA was shown to occur during incubation with commercially purified DNase. Most of the RNase activity could be removed by passage of the DNase through a column of agarose-coupled amino phenylphosphoryl-uridine-2' (3')-phosphate. Incubation with the treated DNase caused only minimal alteration of the sedimentation pattern of high molecular weight nuclear RNA, determined under partially denturing conditions. No impairment of DNase activity was detected.

Chromatography, Affinity↗
PubMed1976

Elimination of double strand nuclease activity from S1 nuclease prepared from crude alpha amylase.

Single strand-specific s1 nuclease prepared as previously described from crude alpha amylase by DEAE-cellulose chromatography also contains nuclease which degrades double strand nucleic acid. The double strand activity can be removed by repeating the DEAE-cellulose chromatography procedure at least two additional times. S1 nuclease prepared by this procedure does not degrade double strand sheared DNA as measured by Sephadex chromatography. Under the same conditions single strand DNA is completely degraded. Thus, S1 nuclease prepared by this procedure is suitable for use in removing single strand regions in DNA/DNA duplexes and DNA/RNA hybrids.

Amylases↗
PubMed1971

Transcription of nonrepeated DNA in mouse brain.

Under normal conditions of DNA renaturation, about 60 percent of mouse DNA fragments renature at a rate consistent with their being present only once per sperm. These nonrepeated sequences (also called single-copy or unique) may be used in RNA-DNA hybridization experiments to provide quantitative estimates of RNA diversity. About 10 percent of the mouse single-copy sequences are transcribed in mouse brain tissue. Estimates of about 3 percent were obtained for mouse liver and kidney RNA's. If only one of the complementary DNA strands is transcribed, this hybridization value implies that the equivalent of at least 300,000 different sequences of 1000 nucleotides are expressed in mouse brain tissue. It is suggested that the large amount of DNA in mammals is functionally important, and that a substantial proportion of the genome is expressed in the brain.

Animals↗
PubMed1969

Organ-specific estrogen-induced RNA synthesis resolved by DNA-RNA hybridization in the domestic fowl.

In the domestic fowl and other oviparous vertebrates, estrogens induce hepatic synthesis of yolk proteins. The oviduct also increases in size and produces ovalbumin when estrogens are administered. DNA-RNA hybridization assays indicate that within 105 minutes following treatment with estrone the liver of immature pullets contains most, if not all, of the liver RNA species that are present in the livers of the laying hen. Because of limitations of the nucleic acid hybridization technique, which remain to be clearly defined, it is not known whether the hepatic RNA populations in estrone-treated pullets and laying hens are completely homologous or differ in some important way. The results indicate that the genomic response in the avian liver to exogenous estrone is "normal" (relative to the laying hen) and further suggest that the hepatic response to estrogen is primarily pertinent to vitellinogenesis.DNA-RNA hybridization assays on total RNA also indicate that estrogen-induced RNA species in the liver are not homologous to estrogen-evoked RNA species of the oviduct. Therefore, in these two target organs estrogen-evoked RNA synthesis appears to be in part organ-specific. These data indicate that the specificity of hormone action can be explained in part on the basis of induced synthesis of specific RNA molecules. Whether these alterations in transcription are due to indirect hormonal action or are the result of a primary action of estrogens or estrogen-binding site complexes on the genome and/or its repressors remains a basic question.

Animals↗