p16INK4A R24P mutant is produced by a missense mutation in the CDKN2A gene that leads to substution of arginine with proline at position 24. This mutation occurs in the first exon of p16INK4A and therefore does not affect p14ARF. p16INK4A R24P is unable to bind to CDK4 but retains the ability to bind to CDK6 and is therefore partially functional (Harland et al. 1997, Becker et al. 2001, Jones et al. 2007).
p16INK4A G23D mutant is produced by a missense mutation in the CDKN2A gene that lead to substitution of glycine with aspartic acid residue at position 23. This mutation occurs in the first exon of p16INK4A and therefore does not affect p14ARF. p16INK4A G23D mutant shows a reduced ability to bind to CDK4 and prevent CDK4-mediated phosphorylation of RB1 (Scaini et al. 2009)