Figure 4.

Schematic representation of the RIANS model in cells from Category 1 cancer syndromes. (A) First subcategory: Mutated genes are crucial for DNA damage recognition and repair. In this case, the genomic instability is so high that some spontaneous mutations may also affect cell cycle checkpoint control. (B) Second subcategory: Mutated genes are involved in DNA damage recognition and repair but are not crucial. The encoded proteins are X-proteins. The RIANS is delayed by the cytoplasmic overexpression of X-proteins, and few ATM monomers enter in the nucleus. Consequently, CHK proteins are not phosphorylated, and therefore G1/G2 arrests are impaired.