Figure 6. Protein comparison of nvp63 to hup63 and gene structure comparison of N. vectensis p53 protein family to hup63.

A Protein sequence comparison between the human TAp63α (hup63) and nvp63. Highly identical regions comprise the N-terminus, the core DNA binding domain, the tetramerization domain, and the C-terminus. Several SQ motifs are present within the first 23 amino acids at the N-terminus. These motifs were identified in vertebrates as possible phosphorylation sites for DNA damage-induced kinases ATM or ATR [50], [51]. This potentially regulatory part of the protein is followed by a glutamate/aspartate rich amino acid sequence which is common to transcriptional activation domains (not shown in sequence comparison). Like in other invertebrates, nvp63 lacks the amino acid motif (WxxΨF) otherwise present in the transactivation domain of vertebrate p53 family members. B Schematic representation of the nvp63, nvpVS53, nvpEC53, and human hup63 gene. All three p53-like genes were assembled according to the cDNA sequences determined by 5′ and 3′ RACE experiments. The nvp63 gene includes 14 exons (boxes) of which 11 exons encode the nvp63 protein (open boxes). 5′ and 3′ non-translated sequences are indicated by black boxes. The arrow depicts the transcriptional start site. The transactivation domain (TAD), the DNA binding domain (DBD), the oligomerization domain (OD), sterile alpha motif domain (SAM), and the transactivation inhibitory domain (TID) are boxed in yellow, red, green, blue and light grey respectively. Greek letters indicate alternative splice variants identified for hup63. ΔN indicates a cryptic transcriptional start site in intron 3 of the human p63 gene. Four introns interspersed within the DNA binding domain and one intron at the N-terminus of the tetramerization domain in nvp63 are at identical positions as in vertebrates. The nvpEC53 gene has acquired one more splice site within the 5′ end of the DNA binding domain and comprises in total more exons than the two other sea anemone genes nvp63 and nvpVS53. One of the introns conserved from nvp63 to human p63 within the DNA binding domain is absent in nvpVS53. The C-terminal variants of nvpVS53 identified so far are devoid of the canonical OD and putative TID. The observed alternative 3′ exon (exon 9) for nvpVS53 may translate a protein with altered DNA binding capacity. Alternatively, additional splicing patterns might exist during specific developmental stages.