Opposing kinetic effects of an acidic nucleolar phosphoprotein from <i>Physarum polycephalum</i> on homologous and heterologous transcription systems

Atmar, Valerie J.; Daniels, Gary R.; Kuehn, Glenn D.; Braun, Richard

doi:10.1016/0014-5793(80)81115-x

Cited by 6 publications

(3 citation statements)

References 17 publications

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“…Furthermore, several correlations have been established between the increase in intracellular levels of polyamines and stimulation of pre-rRNA synthesis (Tabor & Tabor, 1984). Ornithine decarboxylase plays a key role in polyamine metabolism and has been shown to act directly on rDNA transcription in Xenopus laevis (Atmar et al, 1980;Russell, 1983). From these results and from the data presented in this paper, we propose the following model of regulation of rDNA transcription: in its unphosphorylated form, nucleolin acts as an inhibitor of rDNA transcription.…”

Section: Discussionmentioning

confidence: 65%

Phosphorylation of nucleolin by a nucleolar type NII protein kinase

Caizergues‐Ferrer

Bélenguer²,

Lapeyre³

et al. 1987

Biochemistry

151

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Nucleolin [C23 or 100 kilodaltons (kDa)] is the major nucleolar phosphorylated protein in exponentially growing Chinese hamster ovary cells. A nucleolar cyclic nucleotide independent protein kinase copurified with nucleolin in a complex which could be dissociated by hydroxyapatite chromatography. The kinase was stimulated by spermine and inhibited by heparin and presented most of the properties of nuclear casein kinase NII. Kinetic analyses showed the apparent Km value for nucleolin (7 X 10(-4) mg/mL) to be lower than those for other casein kinase II substrates such as nuclear protein HMG 14 (0.15 mg/mL), topoisomerase I (0.025 mg/mL), or topoisomerase II (0.04 mg/mL). Similarly, Vmax values were higher for nucleolin than for other substrates. Nucleolin thus appears to be a natural preferential substrate of nucleolar casein kinase NII. The kinase phosphorylated nucleolin in vitro at serine residues in a 29-kDa CNBr fragment located near the amino terminus of the molecule. The enzyme labeled typical casein kinase II sites. These sites were found predominantly in two highly acidic tryptic fragments designated A (residues 21-49) and C (residues 180-221) which contained serines having at least two acidic residues on their carboxyl-terminal sides. These results demonstrate the existence in the nucleolus of a type of NII protein kinase that uses a protein involved in ribosome assembly as preferential substrate.

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Section: Discussionmentioning

confidence: 65%

Phosphorylation of nucleolin by a nucleolar type NII protein kinase

Caizergues‐Ferrer

Bélenguer²,

Lapeyre³

et al. 1987

Biochemistry

151

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“…OrnDCase and the Mr 70,000 nonhistone protein, previously investigated by our laboratory (11)(12)(13)(14)24) are shown here to be the same protein. Identity was established in the following properties: catalytic capacity to decarboxylate L-ornithine, amino acid composition, subunit polypeptide Mr, capacity to serve as unique protein substrates for a polyamine-dependent protein kinase, and immunological crossreactivity.…”

Section: Discussionmentioning

confidence: 78%

Phosphorylation of ornithine decarboxylase by a polyamine-dependent protein kinase.

Atmar¹,

Kuehn²

1981

Proc. Natl. Acad. Sci. U.S.A.

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“…The physiological role of ODC in the nucleus of barley seeds remains to be elucidated. An acidic phosphoprotein has been identified in nucleoli of Physarum polycephalum, which is tightly bound to ribosomal DNA (rDNA) and has been shown to possess ODC activity [22]. The suggestion has been put forward that the protein kinase which catalyzes the phosphorylation of this protein is polyaminedependent, with properties similar to those of ODC antizyme [23].…”

Section: Discussionmentioning

confidence: 99%