TAp63 represses transcription of MYCN/NCYM gene and its high levels of expression are associated with favorable outcome in neuroblastoma

Abstract

TAp63 is an isoform of p63 gene, a p53 family gene that suppresses tumorigenesis via transcriptional regulation. TAp63 represses transcription of MYC oncogene in glioblastomas; however, its role in another MYC family gene, MYCN, has remained elusive. In this study, we showed that TAp63 repressed transcription of the MYCN gene in human cancer cells. Overexpression of TAp63 in HeLa cells suppressed MYCN expression, whereas knockdown of TAp63 had the opposite effect. By binding to exon 1 of MYCN gene, TAp63 suppressed the promoter activities of MYCN and its cis-antisense gene, NCYM. Other p53 family members, p53 and TAp73, showed lesser ability to suppress MYCN/NCYM promoter activities compared with that of TAp63. All-trans-retinoic acid (ATRA) treatment of MYCN/NCYM-amplified neuroblastoma CHP134 cells induced TAp63 and reduced p53 expressions, accompanied by downregulation of MYCN/NCYM expressions. Meanwhile, TAp63 knockdown inhibited ATRA-induced repression of NCYM gene expression. Blocking the p53 family binding sites by CRISPR-dCas9 system in CHP134 cells induced MYCN/NCYM expression and promoted apoptotic cell death. Expression levels of TAp63 mRNA inversely correlated with those of MYCN/NCYM expression in primary neuroblastomas, which was associated with a favorable prognosis. Collectively, TAp63 repressed MYCN/NCYM bidirectional transcription, contributing to the suppression of neuroblastoma growth.

Keywords: CRISPR; ChIP; Chromatin immunoprecipitation; Clustered regularly interspaced short palindromic repeat; MYCN; NCYM; Neuroblastoma; Small hairpin RNA; Small interfering RNA; p53; p63; p73; shRNA; siRNA.