Gene

Cell biology

Sequence motif

Biology

Biochemistry

Acoustics

Computational biology

Physics

Structural motif

Genome

Motif (music)

Chemistry

Human genome

Nature Chemistry

Human genome function is underpinned by the primary storage of genetic information in canonical B-form DNA, with a second layer of DNA structure providing regulatory control. I-motif structures are thought to form in cytosine-rich regions of the genome and to have regulatory functions; however, in vivo evidence for the existence of such structures has so far remained elusive. Here we report the generation and characterization of an antibody fragment (iMab) that recognizes i-motif structures with high selectivity and affinity, enabling the detection of i-motifs in the nuclei of human cells. We demonstrate that the in vivo formation of such structures is cell-cycle and pH dependent. Furthermore, we provide evidence that i-motif structures are formed in regulatory regions of the human genome, including promoters and telomeric regions. Our results support the notion that i-motif structures provide key regulatory roles in the genome. I-motif DNA structures are thought to form in cytosine-rich regions of the genome and to have regulatory functions; however, in vivo evidence for the existence of such structures has so far remained elusive. Now an engineered antibody that is selective for i-motif structures has been developed and used to detect i-motifs in the nuclei of human cells.

I-motif DNA structures are formed in the nuclei of human cells