Cisplatin is one of the most potent antitumor agents known, displaying clinical activity against a wide variety of solid tumors. Its cytotoxic mode of action is mediated by its interaction with DNA to form DNA adducts, primarily intrastrand crosslink adducts, which activate several signal transduction pathways, including those involving ATR, p53, p73, and MAPK, and culminate in the activation of apoptosis. DNA damage-mediated apoptotic signals, however, can be attenuated, and the resistance that ensues is a major limitation of cisplatin-based chemotherapy. The mechanisms responsible for cisplatin resistance are several, and contribute to the multifactorial nature of the problem. Resistance mechanisms that limit the extent of DNA damage include reduced drug uptake, increased drug inactivation, and increased DNA adduct repair. Origins of these pharmacologic-based mechanisms, however, are at the molecular level. Mechanisms that inhibit propagation of the DNA damage signal to the apoptotic machinery include loss of damage recognition, overexpression of HER-2/neu, activation of the PI3-K/Akt (also known as PI3-K/PKB) pathway, loss of p53 function, overexpression of antiapoptotic bcl-2, and interference in caspase activation. The molecular signature defining the resistant phenotype varies between tumors, and the number of resistance mechanisms activated in response to selection pressures dictates the overall extent of cisplatin resistance.

/pdf/cisplatin-mode-of-cytotoxic-action-and-molecular-basis-of-57e8cf7is5.pdf

Cisplatin: mode of cytotoxic action and molecular basis of resistance

The DJ-1 gene encodes a ubiquitous, highly conserved protein. Here, we show that DJ-1 mutations are associated with PARK7, a monogenic form of human parkinsonism. The function of the DJ-1 protein remains unknown, but evidence suggests its involvement in the oxidative stress response. Our findings indicate that loss of DJ-1 function leads to neurodegeneration. Elucidating the physiological role of DJ-1 protein may promote understanding of the mechanisms of brain neuronal maintenance and pathogenesis of Parkinson's disease.

https://science.sciencemag.org/content/sci/299/5604/256.full.pdf

Mutations in the DJ-1 Gene Associated with Autosomal Recessive Early-Onset Parkinsonism

The p53 tumor suppressor protein is activated and phosphorylated on serine-15 in response to various DNA damaging agents. The gene product mutated in ataxia telangiectasia, ATM, acts upstream of p53 in a signal transduction pathway initiated by ionizing radiation. Immunoprecipitated ATM had intrinsic protein kinase activity and phosphorylated p53 on serine-15 in a manganese-dependent manner. Ionizing radiation, but not ultraviolet radiation, rapidly enhanced this p53-directed kinase activity of endogenous ATM. These observations, along with the fact that phosphorylation of p53 on serine-15 in response to ionizing radiation is reduced in ataxia telangiectasia cells, suggest that ATM is a protein kinase that phosphorylates p53 in vivo.

https://science.sciencemag.org/content/sci/281/5383/1677.full.pdf

Activation of the ATM Kinase by Ionizing Radiation and Phosphorylation of p53

http://web.mit.edu/biology/guarente/references/6.pdf

Negative Control of p53 by Sir2α Promotes Cell Survival under Stress

There are provided antibodies directed against
the ATM protein are peptide derivatives of the protein are
also provided. Also provided is a diagnostic tool for
determining the presence of A-T having a detector for
detecting ATM protein levels and quantification tools for
analyzing the ATM protein levels. A kit for detecting the
presence of A-T containing a detector for detecting ATM
protein levels and a quantificator for analyzing ATM
protein levels is also provided.

https://science.sciencemag.org/content/sci/281/5383/1674.full.pdf

Enchanced phosphorylation of P53 by ATM in response to DNA damage

DNA Damage-Induced Phosphorylation of p53 Alleviates Inhibition by MDM2

DJ-1, a novel oncogene which transforms mouse NIH3T3 cells in cooperation with ras.

Polyclonal antibodies were produced and purified that selectively react with a p53 epitope containing the murine phosphoserine-389 or the human phosphoserine-392 residue, but not the unphosphorylated epitope. These antibodies, termed alpha-392, were employed to demonstrate that the phosphorylation of this serine-389 residue in the p53 protein occurs in vivo in response to ultraviolet radiation of cells containing the p53 protein. After ultraviolet radiation of cells in culture, p53 levels increase and concomitantly serine-389 is phosphorylated in these cells. By contrast, the serine-389 phosphorylation of the p53 protein was not detected by these antibodies in the increased levels of p53 protein made in response to γ radiation or the treatment of cells with etoposide. These results demonstrate an ultraviolet responsive and specific phosphorylation site at serine-389 of the mouse or serine-392 of the human p53 protein. Previous studies have demonstrated that this phosphorylation of p53 activates the protein for specific DNA binding. This study demonstrates in vivo a unique phosphorylation site in the p53 protein that responds to a specific type of DNA damage.

https://www.pnas.org/content/pnas/95/11/6399.full.pdf

Ultraviolet radiation, but not γ radiation or etoposide-induced DNA damage, results in the phosphorylation of the murine p53 protein at serine-389

Isolation and Characterization of cDNA for DREF, a Promoter-activating Factor for Drosophila DNA Replication-related Genes

Background :T he c-myc proto-oncogene has been suggested to play key roles in cell proliferation, differentiation, transformation and apoptosis. A variety of functions of C-MYC, the product of cmyc, are attributed to protein‐protein interactions with various cellular factors including Max, YY1, p107, Bin1 and TBP. Max and YY1 bind to the Cterminal region of C-MYC, while p107, Bin1 and TBP bind to the N-terminal region covering myc boxes. The N-terminal region is involved in all the biological functions of C-MYC, and different proteins are therefore thought to interact with the N-terminal region of C-MYC to display different functions. Results: We cloned two cDNAs which encode a novel C-MYC-binding protein of 11 kDa, designated AMY-1 (Associate of C-MYC). The two cDNAs, AMY-1L and AMY-1S, derived from alternative usage of polyadenylation signals, code for the same protein of 11 kDa. AMY-1 was bound via its C-terminal region to the N-terminal region of CMYC (amino acids nos 58‐148) corresponding to the transactivation domain. AMY-1 was localized in the cytoplasm in cells expressing c-myc at low levels, but in the nucleus in the cells of a high c-myc expression in transiently transfected cells. A similar difference in endogenous AMY-1 localization was observed during the cell cycle: AMY-1 translocated from cytoplasm to nucleus during the S phase when c-myc expression was increased. AMY-1 by itself did not recognize the E-box element, the MYC/Max binding sequence, nor did it transactivate via the element, but stimulated the activation of E-boxregulated transcription by MYC/Max. FISH analyses revealed that the amy-1 gene was located at 1p32.2‐1p33 in human genome. Conclusions: AMY-1 is a 11 kDa protein which binds to the N-terminal region of C-MYC and stimulates the activation of E-box-dependent transcription by C-MYC. AMY-1, which mostly localizes in the cytoplasm, translocates into the nucleus in the S phase of the cell cycle upon an increase of c-myc expression, and may thus control the transcriptional activity of C-MYC.

Masako Ikeda

Papers

DNA Damage-Induced Phosphorylation of p53 Alleviates Inhibition by MDM2

DJ-1, a novel oncogene which transforms mouse NIH3T3 cells in cooperation with ras.

Ultraviolet radiation, but not γ radiation or etoposide-induced DNA damage, results in the phosphorylation of the murine p53 protein at serine-389

Isolation and Characterization of cDNA for DREF, a Promoter-activating Factor for Drosophila DNA Replication-related Genes

AMY‐1, a novel C‐MYC binding protein that stimulates transcription activity of C‐MYC