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Biomedical subjects

W Keller

Publications and source records attributed to W Keller.

At least 145 records · Page 8Linked to original sources
PubMed1973

Transcription of simian virus 40. 3. Mapping of "early" and "late" species of RNA.

To determine the orientation of transcription of the E and L strands of DNA from simian virus 40 (SV40), we used linear DNA prepared by cleavage of superhelical viral DNA by endonuclease R.R(1) from Escherichia coli as a primer.template for DNA polymerase. The resulting molecules, which were labeled only at the 3' end of each DNA strand, were then cleaved with Hemophilus parainfluenzae endonuclease Hpa I. The ensuing four DNA fragments, whose locations on the viral genome are known, were separated by electrophoresis, denatured, and hybridized to asymmetric SV40 complementary RNA. From the pattern of hybridization of the fragments containing the labeled 3' ends, we conclude that transcription of SV40 proceeds in a clockwise direction on the L strand and in a counterclockwise direction on the E strand as drawn on the conventional SV40 map. To map the "early" and "late" regions of the viral genome, we extracted RNA from lytically infected cells and hybridized it to the separated strands of the four fragments of (32)P-labeled SV40 DNA. Early after infection, RNA complementary to part of the E strand of the contiguous fragments A and C was detected. Late polysomal RNA was complementary to part of the L strand sequences of fragments A and C and to the total L strand sequence of fragments B and D.

Animals↗
PubMed1972

Degradation of DNA RNA hybrids by ribonuclease H and DNA polymerases of cellular and viral origin.

Ribonuclease H from human KB cells, chick embryos, calf thymus, avian myeloblastosis virus, and Rous associated virus specifically degrades the RNA of DNA.RNA hybrids, producing mono- and oligoribonucleotides terminated in 5'-phosphates. The cellular RNase H is an endonuclease, whereas the viral enzyme appears to be an exonuclease. Viral DNA polymerase and RNase H copurify through all separation steps. Therefore, RNase H activity is an intrinsic part of the viral DNA polymerase. DNA.RNA hybrids are also degraded by nucleases associated with cellular DNA polymerases and by exonuclease III. However, these nucleases differ from RNase H in their ability to degrade both strands of DNA.RNA hybrids.

Animals↗
PubMed1972

RNA-primed DNA synthesis in vitro.

In vitro DNA synthesis on single-stranded circular DNA can be initiated by RNA primers. RNA chains are covalently extended by DNA polymerase II from KB cells and DNA polymerase I from Micrococcus luteus, but not by an RNA-dependent DNA polymerase from avian myeloblastosis virus. The reaction product consists of DNA chains with a piece of RNA at their 5'-ends, hydrogen bonded to the template DNA. The primer RNA is linked to the product DNA via a 3':5'-phosphodiester bond, and can be specifically removed by ribonuclease H. The possible role of ribonuclease H in RNA-primed DNA synthesis in vivo is discussed.

Avian Leukosis Virus↗
PubMed1966

Work and food.

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Calorimetry↗