Calf thymus nuclei

Zaitsev, S.V., Haberland, A., Otto, A., Vorob ev, V.I., Haller, H., Bottger, M. (1997). HI and HMG17 extracted from calf thymus nuclei are efficient DNA carriers in gene transfer. Gene Ther., 4, 586-592. 

Fig. 4. (right) Possible cleavage sites of poly(ADP-ribose) synthetase in calf thymus nuclei. 

Klouwen and his associates [38, 39] have further investigated the occurrence of oxidative phosphorylation in thymus nuclei they acknowledge contamination of the nuclear pellet with as much as 10% intact cell. Yet they believe that the small levels of oxidative phosphorylation measured in nuclei (P/O ratio 0.6-1.0) do not result from contamination by intact or fragmented mitochondria. Further, they claim that the nuclear oxidative phosphorylation is sensitive to various inhibitors of the electron transport chain. Using low-temperature spectophotometry, it was established that a nuclear preparation free of cytoplasmic contamination contained cytochrome b, c, and aa3 and that as much as 40% of cytochrome aa3 may be found in association with calf thymus nuclei. Other researchers have also found cytochrome b and c, but not cytochrome aa3, in calf thymus nuclear preparations. 

Chloramphenicol has been reported to have no effect on amino acid activation or incorporation of amino acids into sRNA. In high concentration, however, it inhibits nearly completely the incorporation of labelled amino acid into the protein of calf thymus nuclei . The antibiotic thus appears to interfere at a late stage in the process of protein synthesis. It is of interest that its L-erythro isomer has bttle effect on protein synthesis but inhibits the synthesis of a D-glutamyl pol5q>eptide by Bacillus suhtilis. ... 

Fig. 7 Identification of novel posttranslational modifications of histones H2A and H2B isolated from calf thymus nuclei by FT-ICR MS analysis of proteolytic peptides generated by the digestion of histone H2A with pepsin (a) or trypsin (b), and of histone H2B with trypsin (c) and V8DE (d). Reproduced from [375]...

Poly A polyinerase an enzyme which spedfically catalyses the synthesis of poly A sequences, a process which does not require DNA. P. from calf thymus has M, about 150,000. It is localized in the nucleus, and is responsible for the covalent attachment of poly A sequences to RNA (see Polyadenylic acid). 

Poly A does not exist in an isolated form in the nucleus and must, therefore, be added to preexisting polynucleotide chains. Thus, when hnRNA molecules have been transcribed, they serve as primer for the biosynthesis of their poly A tail at the 3 -end. Inasmuch as they are no poly (dT) or poly (dA) regions in the DNA, it seems clear that poly A is not synthesized by the traditional transcription mechanisms. Moreover, the enzymes that synthesize poly A are sensitive to cordycepin, which has no or little effect on mRNA synthesis. The enzymes responsible for poly A synthesis have been purified to gel electrophoretic homogeneity from calf thymus in Mary Edmonds laboratory [196]. 

The mutagenic properties of LSD-25 are now demonstrated and physicochemical studies by circular dichroism have shown direct interactions of LSD with calf-thymus DNA. Fluorescence studies also bring supporting evidence that indole-alkylamines can interact with DNA. Converging data are therefore at hand to support the provocative hypothesis of a direct competition of hallucinogens for tryptaminergic receptors located on DNA molecules in the nucleus or on RNAs located in the plasma membrane. 

Initially discovered in extracts of calf thymus as a contaminating enzyme during the purification of RNA polymerase (1,2), RNase H has since been found almost ubiquitously in lower and higher eukaryotes as well as in prokaryotes. A single cell type may have one or more species of RNases H residing in the cell nucleus and/or cytosol. Some RNases H have a single ribonucleolytic reaction specificity, whereas others are associated with DNA polymerase activities. Cellular RNases H, for example, from E. coli and calf thymus, are endonucleases the retroviral reverse transcriptase-associated RNases H can function as both exo- and endoribo-nucleases depending on the type of substrates available. 

The TDTase activity in calf thymus is localized in both cytoplasm and nucleus (1). In immature thymocytes and neoplastic cells, TDTase is observed almost exclusively in the nucleus (54). The structural gene for calf TDTase has been cloned and efficiently expressed from a plasmid expression vector in COS7 (monkey fibroblast) cells (43). 

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