Figure 11

The B/B′ G-quadruplex pair may regulate alternative splicing at the 5′ splice site of human and msouse MECP2 orthologs. The highly conserved G-quadruplex B is found 5 bases upstream of the alternative 5′ splice site in the human MECP2 pre-mRNA sequence and may function as an exonic splicing enhancer (ESE) regulatory motif. The B′ G-quadruplex, which is also highly conserved across the mammalian species, overlaps the B motif as well as the alternative 5′ splice site. At a given time, only one of the G-quadruplex is likely to be formed in the cell. Therefore, B and B′ are likely to be mutually exclusive. G-quadruplex B′ when formed may act as an inhibitor of alternative splicing since formation of this structure is likely to make the 5′ splice site unavailable. Underlined Gs represent the bases involved in the G-tetrad formation in the G-quadruplex. G-quadruplexes B and B′ refer to the corresponding marked map positions in Figure 8. Human and mouse B/B′ G-quadruplex sequence motifs are identical.