Structure and regulation of CD133. (a) CD133 protein structure in which the C-terminal tyrosine-phosphorylation consensus site, which comprises 5 tyrosine residues including Y828 and Y852, and the splice variants regions are indicated. (b) Schematic representation of the 5′ untranslated region of the CD133 gene. Transcription factors that positively (green circles) or negatively (red circles) regulate CD133 expression by direct binding to the different promoters are reported. The direct binding of Notch1 to the site for RBP-Jk located upstream P1–P5 promoters is also indicated.