Figure 5.

Putative model of p53 post-transcriptional regulation in a heterologous yeast context. (A) In the presence of the 5′-UTR, a complex structure is formed [two possibilities are represented: (1) a ‘pseudoknot’ structure, (2) a coaxial stacking of two stems] and strongly inhibits either the initiation or the progression of the ribosome across the stem–loop structure. Therefore, only the p40 truncated protein is produced at a low level. (B) In the absence of 5′-UTR, only a weak stem–loop is formed that could often be bypassed by the ribosome, giving rise to a large quantity of the 53 kDa protein, but sometimes the ribosome is arrested and led to a weak quantity of p40 protein. Due to the absence of structure at the 5′ end, the initiation of translation is highly improved. Complete 5′-UTR (green); p53 ORF (red); first 154 bases of 3′-UTR (blue).