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Western blot analysis of extracts from HeLa cells, transfected with 100 nM SignalSilence® Control siRNA (Fluorescein Conjugate) #6201 (-) or SignalSilence® p53 siRNA II (+), using p53 (1C12) Mouse mAb #2524 and β-Actin (13E5) Rabbit mAb #4970. p53 (1C12) Mouse mAb confirms silencing of p53 expression and β-Actin (13E5) Rabbit mAb is used to control for loading and specificity of p53 siRNA.

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Product Usage Information

CST recommends transfection with 100 nM p53 siRNA II 48 to 72 hours prior to cell lysis. For transfection procedure, follow protocol provided by the transfection reagent manufacturer. Please feel free to contact CST with any questions on use.

Each vial contains the equivalent of 100 transfections, which corresponds to a final siRNA concentration of 100 nM per transfection in a 24-well plate with a total volume of 300 μl per well.


Storage: SignalSilence® siRNA is supplied in RNAse-free water. Aliquot and store at -20ºC.

Product Description

SignalSilence® p53 siRNA from Cell Signaling Technology (CST) allows the researcher to specifically inhibit p53 expression using RNA interference, a method whereby gene expression can be selectively silenced through the delivery of double stranded RNA molecules into the cell. All SignalSilence® siRNA products are rigorously tested in-house and have been shown to reduce target protein expression by western analysis.


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).


1.  Levine, A.J. (1997) Cell 88, 323-31.

2.  Meek, D.W. (1994) Semin Cancer Biol 5, 203-10.

3.  Milczarek, G.J. et al. (1997) Life Sci 60, 1-11.

4.  Shieh, S.Y. et al. (1997) Cell 91, 325-34.

5.  Chehab, N.H. et al. (1999) Proc Natl Acad Sci U S A 96, 13777-82.

6.  Honda, R. et al. (1997) FEBS Lett 420, 25-7.

7.  Shieh, S.Y. et al. (1999) EMBO J 18, 1815-23.

8.  Hirao, A. et al. (2000) Science 287, 1824-7.

9.  Hao, M. et al. (1996) J Biol Chem 271, 29380-5.

10.  Tibbetts, R.S. et al. (1999) Genes Dev 13, 152-7.

11.  Lu, H. et al. (1997) Mol Cell Biol 17, 5923-34.

12.  Ullrich, S.J. et al. (1993) Proc Natl Acad Sci U S A 90, 5954-8.

13.  Kohn, K.W. (1999) Mol Biol Cell 10, 2703-34.

14.  Lohrum, M. and Scheidtmann, K.H. (1996) Oncogene 13, 2527-39.

15.  Knippschild, U. et al. (1997) Oncogene 15, 1727-36.

16.  Oda, K. et al. (2000) Cell 102, 849-62.

17.  Ito, A. et al. (2001) EMBO J 20, 1331-40.

18.  Sakaguchi, K. et al. (1998) Genes Dev 12, 2831-41.

19.  Solomon, J.M. et al. (2006) Mol Cell Biol 26, 28-38.


Entrez-Gene Id 7157
Swiss-Prot Acc. P04637


For Research Use Only. Not For Use In Diagnostic Procedures.
Cell Signaling Technology is a trademark of Cell Signaling Technology, Inc.
SignalSilence is a registered trademark of Cell Signaling Technology, Inc.
Limited Use Label License, RNA interference: This product is licensed under European Patent 1144623 and foreign equivalents from Ribopharma AG, Kulmbach, Germany and is provided only for use in non-commercial research specifically excluding use (a) in drug discovery or drug development, including target identification or target validation, by or on behalf of a commercial entity, (b) for contract research or commercial screening services, (c) for the production or manufacture of siRNA-related products for sale, or (d) for the generation of commercial databases for sale to Third Parties. Information about licenses for these and other commercial uses is available from Ribopharma AG, Fritz-Hornschuch-Str. 9, D-95326 Kulmbach, Germany.