p53: guardian of reprogramming.

The reprogramming of somatic cells to induced pluripotent stem (iPS) cells is one of the major discoveries of recent years. The development and application of patient specific iPS lines could potentially revolutionise cell-based therapy, facilitating the treatment of a wide range of diseases. Despite the numerous technological advancements in the field, an in-depth mechanistical understanding of the pathways involved in reprogramming is still lacking. Several groups have recently provided a mechanistical insight into the role of the p53 tumour suppressor pathway in reprogramming. The repercussions of these findings are profound and reveal an unexpected role of p53 as a "guardian of reprogramming", ensuring genomic integrity during reprogramming at the cost of a reduced efficiency of the process. Here we analyse the latest findings in the field and discuss their relevance for future applications of iPS cell technology.