H19 and Igf2 monoallelic expression is regulated in two distinct ways by a shared cis acting regulatory region upstream of H19

Article Abstract:

H19 and Igf2 monoallelic expression is regulated in two distinct ways by a shared cis acting regulatory region upstream of H19. Study has been done using a loxP/cre recombinase-based strategy to delete the upstream region in mice in a conditional way to determine the temporal requirement of the upstream region in starting and maintaining the imprinted expression of H19 and Igf2.

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A transcriptional insulator at the imprinted H19/Igf2 locus

Article Abstract:

A transcriptional insulator has been shown to exist at the imprinted H19/Igf2 locus. The insulator has been characterized in vitro and shown to be neither enhancer- nor promoter-specific. Ifg2 is from the paternal chromosome and H19 is from the maternal one. Mechanisms by which the region silences the maternal Igf2 allele have been studied with the finding that deletion of the region can bring on high levels of activation of H19 and Igf2 from one chromosome. If the cis element is put between a promoter and its enhancer at a heterologous position, the sequences have insulator activity and also can be stably imprinted.

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Nuclear matrix attachment regions antagonize methylation-dependent repression of long-range enhancer-promoter interactions

Article Abstract:

Nuclear matrix attachment regions have been found to be antagonistic to methylation-dependent repression of long-range enhancer-promoter interactions. Effects of DNA methylation, which happens in early mouse development, on the function of the mu enhancer and the MARS, has been studied. The methylation of rearranged mu genes in vitro, before transfection, cuts back ability of the mu enhancer to activate the V(sub H) promoter over a 1.2-kb distance. Methylation doesn't, however, affect enhancer-mediated promoter activation over 150 bp. DNA methylation can be seen to be detrimental to the distance-independence of enhancer function. It imposes thereby necessity for more regulatory elements which help long-range chromatin remodeling.

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