Mechanism of G1 Radiation Checkpoint Activation Figure 6. Data consolidation. A) Data clustering analysis. Unsupervised clustering based on numerical observations. B) Signalling model. Hits split into groups according to their role in the accumulation of the TP53 target p21CIP1/WAF1. Canonical double strand signalling components (ATM, ATR, CHK1/2) affecting the TP53/p21CIP1/WAF1 axes in conjunction with S/G2 checkpoint activation do not affect G1 checkpoint function. doi:10.1371/journal.pone.0031627.g006 PLoS ONE | www.plosone.org 10 February 2012 | Volume 7 | Issue 2 | e31627