Skin human papillomavirus type 38 alters p53 functions by accumulation of ΔNp73

The E6 and E7 of the cutaneous human papillomavirus (HPV) type 38 immortalize primary human keratinocytes, an event normally associated with the inactivation of pathways controlled by the tumour suppressor p53. Here, we show for the first time that HPV38 alters p53 functions. Expression of HPV38 E6 and E7 in human keratinocytes or in the skin of transgenic mice induces stabilization of wild-type p53. This selectively activates the transcription of Delta Np73, an isoform of the p53-related protein p73, which in turn inhibits the capacity of p53 to induce the transcription of genes involved in growth suppression and apoptosis. Delta Np73 downregulation by an antisense oligonucleotide leads to transcriptional re-activation of p53-regulated genes and apoptosis. Our findings illustrate a novel mechanism of the alteration of p53 function that is mediated by a cutaneous HPV type and support the role of HPV38 and Delta Np73 in human carcinogenesis.