Distribution of G-quadruplex structures in the promoter regions of mouse, chicken, zebrafish, and human genes.

We computed the distribution of G4 in the promoter (2 kbps upstream of the TSS) of mouse, chicken, zebrafish, and human genes and compared to that of corresponding cyclic genes. As cyclic genes in human are not well defined, we used homologs of mouse cyclic genes for comparison purposes. G4 is significantly represented in the promoter of mouse cyclic genes. Indeed 85% of known mouse cyclic genes contain the G4 structures, suggesting a possible role during mouse somitogenesis. The p-value is computed using Fisher exact test.