Increased PTCHD4 expression via m6A modification of PTCHD4 mRNA promotes senescent-cell survival [RNA-seq]
RNA modifications, including m6A, critically modulate protein expression program in a range of cellular processes.  Although cellular senescence has been linked to age-related diseases and functional declines, the landscape and impact of m6A modification are poorly understood. Here, we report a robust m6A modification of Patched-Domain Containing Protein 4 (PTCHD4) mRNA at m6A in senescent cells.  The METTL3/METTL14 complex was found to mediate the m6A modification of PTCHD4 mRNA, which increased PTCHD4 mRNA stability and PTCHD4 production.  MeRIP RT-qPCR and eCLIP analyses were used to map this m6A modification to the last exon of PTCHD4 mRNA.  Further investigation identified IGF2BP1, but not other m6A readers, as being responsible for stabilization and increased abundance of PTCHD4 mRNA by m6A modification.  Silencing PTCHD4, a transmembrane protein, enhanced growth arrest and DNA damage in pre-senescent cells, and sensitized them to senolytic treatments and apoptosis.  Our results support the notion that m6A modifications critically control senescence programs, and that factors such as METTL3/METTL14 and IGF2BP1, implicated in PTCHD4 mRNA m6A metabolism, could be exploited to eliminate senescent cells for therapeutic benefit. Overall design: To investigate the functions of PTCHD4, the gene was silenced using 2 different methods. Each condition was sequenced in replicates of 3.  PTCHD4 silencing was compared to  control.