Figure 2.

The human/murine INK4a/ARF locus. The INK4a/ARF locus resides on chromosome 9p21 and encodes for two different proteins in human and mouse: p16^INK4a and p14^ARF (named p19^ARF in mouse). The INK4a gene is represented by exons 1α, 2, and 3 and it encodes for p16^INK4a, a 168 amino acids protein in mouse and a 156 amino acids protein in human. The ARF gene is composed by exons 1β, 2, and 3. It encodes for p19^ARF in mouse (169 amino acids) and for p14^ARF in human (132 amino acids). Upstream of the INK4a and ARF genes on the same chromosome, exons 1 and 2 represent the INK4b gene encoding for p15^INK4b.