PCNA and medulloblastoma: A sequence of eight amino acids following the second HHD was identified as a canonical PCNA‐interaction‐protein box (PIP‐box) responsible for RTEL1 interaction with the replisome via PCNA; mutation of the RTEL1 PIP‐box in mice exhibited accelerated tumor formation, increased predisposition to medulloblastoma, and decreased survival (Vannier et al., 2013).