Phospho-p53 (Thr18) Antibody

2529:

Western Blotting

Phospho-p53 (Thr18) Antibody detects endogenous levels of p53 only when phosphorylated at threonine 18.

Polyclonal antibodies are produced by immunizing animals with a synthetic phosphopeptide corresponding to residues surrounding Thr18 of human p53. Antibodies are purified by protein A and peptide affinity chromatography.

Western Blotting

Western blot analysis of extracts from MCF-7 cells treated with doxorubicin (0.5 uM, 24 h) or doxorubicin plus lambda Phosphatase NEB#P0753 (10,000 Units/ml, 1h), using Phospho-p53 (Thr18) Antibody (upper) or p53 Antibody #9282 (lower).

The p53 tumor suppressor protein plays a major role in cellular response to DNA damage and other genomic aberrations. Activation of p53 can lead to either cell cycle arrest and DNA repair or apoptosis (1). p53 is phosphorylated at multiple sites in vivo and by several different protein kinases in vitro (2,3). DNA damage induces phosphorylation of p53 at Ser15 and Ser20 and leads to a reduced interaction between p53 and its negative regulator, the oncoprotein MDM2 (4). MDM2 inhibits p53 accumulation by targeting it for ubiquitination and proteasomal degradation (5,6). p53 can be phosphorylated by ATM, ATR, and DNA-PK at Ser15 and Ser37. Phosphorylation impairs the ability of MDM2 to bind p53, promoting both the accumulation and activation of p53 in response to DNA damage (4,7). Chk2 and Chk1 can phosphorylate p53 at Ser20, enhancing its tetramerization, stability, and activity (8,9). p53 is phosphorylated at Ser392 in vivo (10,11) and by CAK in vitro (11). Phosphorylation of p53 at Ser392 is increased in human tumors (12) and has been reported to influence the growth suppressor function, DNA binding, and transcriptional activation of p53 (10,13,14). p53 is phosphorylated at Ser6 and Ser9 by CK1δ and CK1ε both in vitro and in vivo (13,15). Phosphorylation of p53 at Ser46 regulates the ability of p53 to induce apoptosis (16). Acetylation of p53 is mediated by p300 and CBP acetyltransferases. Inhibition of deacetylation suppressing MDM2 from recruiting HDAC1 complex by p19 (ARF) stabilizes p53. Acetylation appears to play a positive role in the accumulation of p53 protein in stress response (17). Following DNA damage, human p53 becomes acetylated at Lys382 (Lys379 in mouse) in vivo to enhance p53-DNA binding (18). Deacetylation of p53 occurs through interaction with the SIRT1 protein, a deacetylase that may be involved in cellular aging and the DNA damage response (19).

Phosphorylation of p53 at Thr18 by casein kinase 1 has been reported to disrupt p53-MDM2 binding, but phosphorylation at this site requires prior phosphorylation at Ser15 (17,18).

1. Levine, A.J. (1997) Cell 88, 323-331.
2. Meek, D.W. (1994) Semin. Cancer Biol. 5, 203-210.
3. Milczarek, G.J. et al. (1997) Life Sci. 60, 1-11.
4. Shieh, S.Y. et al. (1997) Cell 91, 325-334.
5. Chehab, N.H. et al. (1999) Proc. Natl. Acad. Sci. USA 96, 13777-13782.
6. Honda, R. et al. (1997) FEBS Lett. 420, 25-27.
7. Tibbetts, R.S. et al. (1999) Genes Dev. 13, 152-157.
8. Shieh, S.Y. et al. (1999) EMBO J. 18, 1815-1823.
9. Hirao, A. et al. (2000) Science 287, 1824-1827.
10. Hao, M. et al. (1996) J. Biol. Chem. 271, 29380-29385.
11. Lu, H. et al. (1997) Mol. Cell. Biol. 17, 5923-5934.
12. Ullrich, S.J. et al. (1993) Proc. Natl. Acad. Sci. USA 90, 5954-5958.
13. Kohn, K.W. (1999) Mol. Biol. Cell 10, 2703-2734.
14. Lohrum, M. and Scheidtmann, K.H. (1996) Oncogene 13, 2527-2539.
15. Knippschild, U. et al. (1997) Oncogene 15, 1727-1736.
16. Oda, K. et al. (2000) Cell 102, 849-862.
17. Ito, A. et al. (2001) EMBO J. 20, 1331-1340.
18. Sakaguchi, K. et al. (1998) Genes Dev. 12, 2831-2841.
19. Solomon, J.M. et al. (2006) Mol. Cell. Biol. 26, 28-38.
20. Sakaguchi , K. et al. (2000) J. Biol. Chem. 275, 9278-9283.
21. Dumaz, N. et al. (1999) FEBS Lett. 463, 312-316.

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For Research Use Only. Not For Use In Diagnostic Procedures.