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Biomedical subjects

S Penman

Publications and source records attributed to S Penman.

At least 163 records · Page 9Linked to original sources
PubMed1971

Regulation of protein synthesis in HeLa cells. 3. Inhibition during poliovirus infection.

The mechanism of inhibition of host cell protein synthesis by poliovirus has been studied by examining the behavior of host polyribosomes and polyribosome-associated messenger ribonucleic acid (mRNA). Virus infection appears to result in a specific inhibition of the initiation of translation of host cell mRNA. The site of inhibition does not appear to be mRNA itself. Human cells respond to virus infection by producing a factor antagonistic to the virus inhibition which promotes the initiation of host mRNA translation. The production of the host factor is sensitive to actinomycin; however, the behavior of the host cell factor and that of host mRNA appear distinctly different.

Amino Acids↗
PubMed1970

Mitochondrial RNA synthesis during mitosis.

HeLa cells arrested in metaphase synthesized relatively normal amounts of mitochondrial RNA, while little RNA synthesis associated with the nucleus was detected. The RNA synthesized resembled the portion of mitochondrial RNA sensitive to ethidium bromide in interphase cells, with major peaks at 21, 12, and 4S. Unlike that in interphase cells, RNA synthesis in the mitoclhonidrial fraction of mitotic cells was completely inhibited by ethidium bromide.

Bromides↗
PubMed1970

Messenger and heterogeneous nuclear RNA in HeLa cells: differential inhibition by cordycepin.

Cordycepin (3'-deoxyadenosine) suppresses the labeling of messenger RNA in HeLa cells. The drug has no effect on either the labeling of nuclear heterogeneous RNA or on the transport of messenger RNA into the cytoplasm. The results suggest that messenger RNA and nuclear heterogeneous RNA are synthesized separately, and that the transcription of messenger RNA is inhibited by the drug.

Carbon Isotopes↗
PubMed1969

The cytoplasmic RNA of HeLa cells: new discrete species associated with mitochondria.

Two new species of cytoplasmic RNA with approximate sedimentation values of 12S and 21S, and which appear associated with mitochondria, are described. The species are unmethylated, are relatively metabolically stable, and have a 43 per cent G + C content. Their synthesis is uniquely resistant to inhibition by UV irradiation. The 12S and 21S RNA do not appear to be components of polysome-like structures.

Electrophoresis↗
PubMed1969

The regulation of RNA synthesis and processing in the nucleolus during inhibition of protein synthesis.

The effect of protein synthesis inhibition by cycloheximide on nucleolar RNA synthesis and processing has been studied in HeLa cells. Synthesis of 45S RNA precursor falls rapidly after administration of the drug. However, the nucleolar content of 45S RNA remains relatively constant for at least 1 hr because the time required for cleavage of the precursor molecule into its products is lengthened after treatment with cycloheximide. The efficiency of transformation of 45S RNA to 32S RNA remains constant with approximately one molecule of the 32S RNA produced for each cleavage of a molecule of 45S RNA. However, shortly after the cessation of protein synthesis the formation of 18S RNA becomes abortive. The amount of 32S RNA present in the nucleolus remains relatively constant. After long periods of protein synthesis inhibition the 28S RNA continues to be synthesized and exported to the cytoplasm but at a greatly reduced rate. When the protein synthesis inhibitor is removed, a prompt, although partial, recovery in the synthesis rate of 45S RNA occurs. The various aspects of RNA synthesis regulation and processing are discussed.

Cell Nucleolus↗