A conserved structural element in horse and mouse IGF2 genes binds a methylation sensitive factor.

摘要

The horse IGF2 gene was cloned and characterized. It spanned a 9-kb region; 3 coding exons and 3 untranslated leader exons, all highly homologous to those in other species, were identified. Downstream of the polyadenylation site in exon 6, a dinucleotide repeat sequence was identified. Three putative promoters (P1-P3) were located in the 5' region of the gene. RNase protection analysis revealed 2 active promoters in fetal tissues, P2 and P3, whereas P3 was the only promoter active in adult tissues.This represented a transcriptional pattern different from that in rodents. A novel structural element, an inverted repeat, was predicted in the 3' region of the IGF2 gene. This repeat is conserved between species and located in a region which is differentially methylated in the human and mouse genes and might therefore be involved in the imprinting mechanism. The inverted repeat acquires a stem-loop structure in vitro with a hybrid A/B-DNA conformation in the stem area. Both in horses and mice, a methylation-sensitive protein bound this structure with a strong requirement for the loop area.