Impact of transcriptional mutagenesis on p53 transactivation

The transcriptional error rate can be significantly increased by the presence of DNA lesions that instruct mis-insertion during transcription; a process referred to as transcriptional mutagenesis (TM). Herein, we determined the effect of O6-methylguanine (O6-meG) on transcription and subsequent transactivation activity of p53 in human lung H1299 cells. Levels of TM and effects on transactivation were determined by RNA-seq. Results showed that 47% of all p53 transcripts contained an uridine misincorporation opposite the lesion at 6 h post transfection, which was decreased to 18% at 24 h. TM at these levels reduced DNA binding activity of p53 to 21% and 80% compared to wild type p53, respectively. Gene expression data were analyzed to identify differentially expressed genes due to TM compared to the response of wild type p53. We show a temporal repression of transactivation of >100 high confidence p53 target genes including regulators of the cell cycle, DNA damage response and apoptosis. In addition, TM repressed the transcriptional downregulation by p53 of several negative regulators of proliferation and differentiation . Our work demonstrates that TM, even when restricting its effect to an individual transcription factor, has the potential to alter gene expression programs and diversify cellular phenotypes. Assessment of gene expression profiles in human lung H1299 cells following transfection with wild type, mutant (R248W) or DNA lesion-modified (at codon 248) p53 for 6 and 24 h. Biological triplicates were included for each condition including a control with GFP only expressing vector. A total of 30 samples.