Phosphorylation of Human Rad9 Is Required for Genotoxin-activated Checkpoint Signaling

Pia Roos-Mattjus, Kevin M. Hopkins, Andrea J. Oestreich, Benjamin T. Vroman, Kenneth L. Johnson, Stephen Naylor, Howard B. Lieberman, Larry M Karnitz

Research output: Contribution to journalArticle

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Abstract

Rad9, a key component of genotoxin-activated check-point signaling pathways, associates with Hus1 and Rad1 in a heterotrimeric complex (the 9-1-1 complex). Rad9 is inducibly and constitutively phosphorylated. However, the role of Rad9 phosphorylation is unknown. Here we identified nine phosphorylation sites, all of which lie in the carboxyl-terminal 119-amino acid Rad9 tail and examined the role of phosphorylation in genotoxin-triggered checkpoint activation. Rad9 mutants lacking a Ser-272 phosphorylation site, which is phosphorylated in response to genotoxins, had no effect on survival or checkpoint activation in Mrad9 -/- mouse ES cells treated with hydroxyurea (HU), ionizing radiation (IR), or ultraviolet radiation (UV). In contrast, additional Rad9 tail phosphorylation sites were essential for Chkl activation following HU, IR, and UV treatment. Consistent with a role for Chk1 in S-phase arrest, HU- and UV-induced S-phase arrest was abrogated in the Rad9 phosphorylation mutants. In contrast, however, Rad9 did not play a role in IR-induced S-phase arrest. Clonogenic assays revealed that cells expressing a Rad9 mutant lacking phosphorylation sites were as sensitive as Rad9 -/- cells to UV and HU. Although Rad9 contributed to survival of IR-treated cells, the identified phosphorylation sites only minimally contributed to survival following IR treatment. Collectively, these results demonstrate that the Rad9 phospho-tail is a key participant in the Chk1 activation pathway and point to additional roles for Rad9 in cellular responses to IR.

Original languageEnglish (US)
Pages (from-to)24428-24437
Number of pages10
JournalJournal of Biological Chemistry
Volume278
Issue number27
DOIs
StatePublished - Jul 4 2003

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Phosphorylation
Mutagens
Ionizing radiation
Ionizing Radiation
Hydroxyurea
Ultraviolet radiation
Chemical activation
S Phase
Radiation
Tail
Survival
Cells
Colony-Forming Units Assay
Assays
Amino Acids

ASJC Scopus subject areas

  • Biochemistry

Cite this

Roos-Mattjus, P., Hopkins, K. M., Oestreich, A. J., Vroman, B. T., Johnson, K. L., Naylor, S., ... Karnitz, L. M. (2003). Phosphorylation of Human Rad9 Is Required for Genotoxin-activated Checkpoint Signaling. Journal of Biological Chemistry, 278(27), 24428-24437. https://doi.org/10.1074/jbc.M301544200

Phosphorylation of Human Rad9 Is Required for Genotoxin-activated Checkpoint Signaling. / Roos-Mattjus, Pia; Hopkins, Kevin M.; Oestreich, Andrea J.; Vroman, Benjamin T.; Johnson, Kenneth L.; Naylor, Stephen; Lieberman, Howard B.; Karnitz, Larry M.

In: Journal of Biological Chemistry, Vol. 278, No. 27, 04.07.2003, p. 24428-24437.

Research output: Contribution to journalArticle

Roos-Mattjus, P, Hopkins, KM, Oestreich, AJ, Vroman, BT, Johnson, KL, Naylor, S, Lieberman, HB & Karnitz, LM 2003, 'Phosphorylation of Human Rad9 Is Required for Genotoxin-activated Checkpoint Signaling', Journal of Biological Chemistry, vol. 278, no. 27, pp. 24428-24437. https://doi.org/10.1074/jbc.M301544200
Roos-Mattjus P, Hopkins KM, Oestreich AJ, Vroman BT, Johnson KL, Naylor S et al. Phosphorylation of Human Rad9 Is Required for Genotoxin-activated Checkpoint Signaling. Journal of Biological Chemistry. 2003 Jul 4;278(27):24428-24437. https://doi.org/10.1074/jbc.M301544200
Roos-Mattjus, Pia ; Hopkins, Kevin M. ; Oestreich, Andrea J. ; Vroman, Benjamin T. ; Johnson, Kenneth L. ; Naylor, Stephen ; Lieberman, Howard B. ; Karnitz, Larry M. / Phosphorylation of Human Rad9 Is Required for Genotoxin-activated Checkpoint Signaling. In: Journal of Biological Chemistry. 2003 ; Vol. 278, No. 27. pp. 24428-24437.
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