Phosphorylation sites for type n ii protein kinase in DNA-topoisomerase i from calf thymus

Coderoni, S.; Paparelli, M; Gianfranceschi, G.

doi:10.1016/0020-711x(90)90009-r

Cited by 16 publications

(6 citation statements)

References 27 publications

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“…Hence, TopI purifies as a phosphoprotein and several studies have demonstrated that its in vitro activity and/or CPT susceptibility can be modulated by phosphorylation or dephosphorylation [67], [68], [69], [70], [71]. Phosphorylation of serine residues have been demonstrated to correlate with in vivo activity and the cellular sensitivity to CPT [18], [63], [64], [67], [72], [73]. In particular protein kinase CK2 is suggested to play and important function in regulating cellular CPT response via in vivo phosphorylation of TopI [18], [63].…”

Section: Discussionmentioning

confidence: 99%

Decreased Camptothecin Sensitivity of the Stem-Cell-Like Fraction of Caco2 Cells Correlates with an Altered Phosphorylation Pattern of Topoisomerase I

et al. 2014

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The CD44+ and CD44− subpopulations of the colorectal cancer cell line Caco2 were analyzed separately for their sensitivities to the antitumor drug camptothecin. CD44+ cells were less sensitive to camptothecin than CD44− cells. The relative resistance of CD44+ cells was correlated with (i) reduced activity of the nuclear enzyme topoisomerase I and (ii) insensitivity of this enzyme to camptothecin when analyzed in extracts. In contrast, topoisomerase I activity was higher in extracts from CD44− cells and the enzyme was camptothecin sensitive. Topoisomerase I from the two subpopulations were differentially phosphorylated in a manner that appeared to determine the drug sensitivity and activity of the enzyme. This finding was further supported by the fact that phosphorylation of topoisomerase I in CD44+ cell extract by protein kinase CK2 converted the enzyme to a camptothecin sensitive, more active form mimicking topoisomerase I in extracts from CD44− cells. Conversely, dephosphorylation of topoisomerase I in extracts from CD44− cells rendered the enzyme less active and camptothecin resistant. These findings add to our understanding of chemotherapy resistance in the Caco2 CD44+ cancer stem cell model.

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Section: Discussionmentioning

confidence: 99%

Decreased Camptothecin Sensitivity of the Stem-Cell-Like Fraction of Caco2 Cells Correlates with an Altered Phosphorylation Pattern of Topoisomerase I

et al. 2014

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“…Topo I is known to be a phosphoprotein (32) that copurifies with serine kinase activities that resemble casein kinase II (CKII) (35) and protein kinase C (PKC) (32). Phosphorylation occurs primarily on serine residues in vivo (23,(35)(36)(37) and appears to be necessary for the initial complex formation between topo I and DNA (36). We find that the activity of topo I and its ability to complex with ARF is abolished by treatment with alkaline phosphatase and that activity and complex formation with ARF is restored by treatment with CKII.…”

Section: Discussionmentioning

confidence: 99%

Serine Phosphorylation-Dependent Coregulation of Topoisomerase I by the p14ARF Tumor Suppressor

et al. 2007

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p14ARF (ARF) and topoisomerase I play central roles in cancer and have recently been shown to interact. The interaction activates topoisomerase I, an important target for camptothecin-like chemotherapeutic drugs, but the regulation of the interaction is poorly understood. We have used the H358 and H23 lung cancer cell lines and purified recombinant human topoisomerase I to demonstrate that the ARF/topoisomerase I interaction is regulated by topoisomerase I serine phosphorylation, a modification that regulates topoisomerase I activity. Both cell lines express wild-type ARF and topoisomerase I proteins at equivalent levels, but H23 topoisomerase I, unlike that of H358 cells, is largely devoid of serine phosphorylation, has low activity, and complexes poorly with ARF. The ability of H23 topoisomerase I to complex with ARF can be restored by treatment with the serine kinase, casein kinase II. Consistent with these observations, we show that the response of H23 cells to camptothecin treatment is unaffected by changes in intracellular levels of ARF. However, in H358 and PC-3 cells, which express a serine phosphorylated topoisomerase I that complexes with ARF, ectopic overexpression of ARF causes sensitization to camptothecin, and siRNA-mediated down-regulation of endogenous ARF causes desensitization to camptothecin. These biological responses correlate with increased and decreased levels, respectively, of ARF/topoisomerase I complex and DNA-bound topoisomerase I. Thus, ARF is a serine phosphorylation-dependent coregulator of topoisomerase I in vivo, and it regulates cellular sensitivity to camptothecin by interacting with topoisomerase I. Certain cancer associated defects affecting ARF/topoisomerase I complex formation could contribute to cellular resistance to camptothecin.

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“…Topo I activity is influenced by phosphorylation, which primarily affects serine residues in vivo [11]–[13]. Several serine kinases have been implicated in topo I phosphorylation, including protein kinase C (PKC), cyclin-dependent kinase I (cdk-1), and protein kinase CK2 (formerly casein kinase II) [14], although the roles played by these enzymes in regulating topo I activity are not fully defined.…”

Section: Introductionmentioning

confidence: 99%

CK2-Mediated Hyperphosphorylation of Topoisomerase I Targets Serine 506, Enhances Topoisomerase I–DNA Binding, and Increases Cellular Camptothecin Sensitivity

Bandyopadhyay

Gjerset

2012

PLoS One

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Topoisomerase I is the target for a potent class of chemotherapeutic drugs derived from the plant alkaloid camptothecin that includes irinotecan and topotecan. In this study we have identified a novel site of CK2-mediated topoisomerase I (topo I) phosphorylation at serine 506 (PS506) that is relevant to topo I function and to cellular responses to these topo I-targeted drugs. CK2 treatment induced hyperphosphorylation of recombinant topo I and expression of the PS506 epitope, and resulted in increased binding of topo I to supercoiled plasmid DNA. Hyperphosphorylated topo I was approximately three times more effective than the basal phosphorylated enzyme at relaxing plasmid supercoils but had similar DNA cleavage activity once bound to DNA. The PS506 epitope was expressed in cancer cell lines with elevated CK2 activity, hyperphosphorylated topo I, and increased sensitivity to camptothecin. In contrast, PS506 was not detected in normal cells or cancer cell lines with lower levels of CK2 activity. By experimentally manipulating CK2 activity in cancer cell lines, we demonstrate a cause and effect relationship between CK2 activity, PS506 expression, camptothecin-induced cellular DNA damage, and cellular camptothecin sensitivity. Our results show that the PS506 epitope is an indicator of dysregulated, hyperphosphorylated topo I in cancer cells, and may thus serve as a diagnostic or prognostic biomarker and predict tumor responsiveness to widely used topo I-targeted therapies.

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Phosphorylation sites for type n ii protein kinase in DNA-topoisomerase i from calf thymus

Cited by 16 publications

References 27 publications

Decreased Camptothecin Sensitivity of the Stem-Cell-Like Fraction of Caco2 Cells Correlates with an Altered Phosphorylation Pattern of Topoisomerase I

Decreased Camptothecin Sensitivity of the Stem-Cell-Like Fraction of Caco2 Cells Correlates with an Altered Phosphorylation Pattern of Topoisomerase I

Serine Phosphorylation-Dependent Coregulation of Topoisomerase I by the p14ARF Tumor Suppressor

CK2-Mediated Hyperphosphorylation of Topoisomerase I Targets Serine 506, Enhances Topoisomerase I–DNA Binding, and Increases Cellular Camptothecin Sensitivity

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