Fig. 4

Fragment 2 promoter regulates specifically ISL1 expression through EZH2 and disturbs the normal basal expression of ISL1-DT/ISL1 cluster. (A) Upper panel shows the genomic overview of ISL1 location with 115 bp upstream the reverse orientated ISL1-DT. Black stripe indicates the position of Fragment 2 and the arrow its active orientation. Lower panel displays chromatin interaction from sci-ATAC-seq3 for ISL1 in the fetal ureteric bud cells11. Light blue bridge indicates the interaction of the genomic locus where Fragment 2 resides with the shared promoter region of ISL1 and ISL1-DT (light blue bridge). (B) Human adult RNA-seq shows the expression pattern of ISL1 and ISL1-DT in different tissues. These genes are generally expressed with higher counts for ISL1 and lower for ISL1-DT. (C) qPCR of ISL1 and ISL1-DT with control and EZH2 siRNA shows a reduced signal of ISL1 but unchanged ISL1-DT expression in HEK 293 cells. (D) Proposed molecular mechanism for the expression pattern of ISL1 and ISL1-DT mediated by EZH2. Top panel shows physiological condition, EZH2 binds to the Fragment 2 promoter and specifically enhances ISL1 expression (red arrows). In pathological condition, EZH2 does not bind to the Fragment 2 and the expression of ISL1 is reduced, but not the expression of ISL1-DT.