Phospho-ΔNp63α/microRNA feedback regulation in squamous carcinoma cells upon cisplatin exposure

Abstract

Our previous reports showed that the cisplatin exposure induced the ATM-dependent phosphorylation of ΔNp63a, which is subsequently involved in transcriptional regulation of gene promoters encoding mRNAs and microRNAs in squamous cell carcinoma (SCC) cells upon cisplatin-induced cell death. We showed that phosphorylated (p)-ΔNp63a plays a role in upregulation of pro-apoptotic proteins, while non-p-ΔNp63a is implicated in pro-survival signaling. In contrast to non-p-ΔNp63a, p-ΔNp63a modulated expression of specific microRNAs in SCC cells exposed to cisplatin. These microRNAs were shown to attenuate the expression of several proteins involved in cell death/survival, suggesting the critical role for p-ΔNp63a in regulation of tumor cell resistance to cisplatin. Here, we studied the function of ΔNp63a in transcriptional activation and repression of the specific microRNA promoters whose expression is affected by cisplatin treatment of SCC cells. We quantitatively studied chromatin-associated proteins bound to tumor protein (TP) p63-responsive element, we found that p-ΔNp63a along with certain transcription coactivators (e.g., CARM1, KAT2B, TFAP2A, etc.) necessary to induce gene promoters for microRNAs (630 and 885-3p) or with transcription corepressors (e.g., EZH2, CTBP1, HDACs, etc.) needed to repress promoters for microRNAs (181a-5p, 374a-5p and 519a-3p) in SCC cells exposed to cisplatin.

Phospho-ΔNp63α/microRNA network modulates epigenetic regulatory enzymes in squamous cell carcinomas

“…and modulation of transcription factors (e.g., TP53 and TP63) has also started to emerge, creating a controlled feedback mechanism. 19,28,[76][77][78]85 The miR-29 family was shown to directly target DNMT3A and DNMT3B and indirectly target DNMT1 through regulation of the transactivator SP1 or RBL2, [86][87][88] while miR-148 and miR-140 were shown to target DNMT1 and DNMT3B. [89][90][91] miR-101 was shown to regulate the expression of EZH2, catalytic subunit of the polycomb repressive complex 2, which mediates epigenetic gene silencing by trimethylating histone H3 lysine 27.…”

“…28,38 The ChIP-grade normal rabbit immunoglobulin (IgG, ab37415, Abcam) was used as a negative control. After reversal of formaldehyde cross-linking, RNA-ase A, and proteinase K treatments, IP-enriched DNAs were used for qPCR assays.…”

“…36-39 P-ΔNp63α was also shown to transcriptionally activate or repress the specific microRNA promoters depending on the chromatin components bound to this transcriptional factor in SCC cells upon cisplatin exposure. 28 In this report, we continue our quest to understand the role of the cisplatin-induced TP63-regulated microRNAs in epigenetic regulation and chemoresistance.…”

“…[23][24][25][26] On the other hand, transcriptional deregulation in cancer cells may lead to altered transcription of specific microRNA genes. [27][28][29] For example, miR-34 was shown to be regulated by the tumor protein (TP)-p53 transcription factor, which regulates the cellular response to stress-induced DNA damage, cell cycle, apoptosis, autophagy, and metabolism. 27 microRNAs may also have therapeutic applications, by which cancer-causing microRNAs could be modulated to restore the normal cellular function.…”

p63 threonine phosphorylation signals the interaction with the WW domain of the E3 ligase Itch

“…3,6,14,38. We have previously investigated the molecular mechanism of Itch recognition for the p63 transcription factor 39 in particular, because this powerful transcription factor is crucial for the development of epithelia, 31,[40][41][42][43][44][45] it is involved in cancer, [46][47][48][49][50][51][52][53][54][55][56][57][58][59] and when it is mutated it causes severe genetic diseases.…”