Estrogen Induces Looping Between Tumor Suppressor RIZ Gene Promoter 2 with Exon 9a

NTP1 Background: The dynamic intra- and inter-chromosomal links between specific loci contribute to the creation of cell type-specific gene expression profiles and to gene regulation during differentiation processes. Looping is implicated in bringing together far upstream or downstream regions with the gene promoter and body sites, and in establishing contacts between the 5' and 3' ends of genes, since 3' end-processing factors interact with components of the transcriptional machinery. The tumor suppressor PRDM2/RIZ gene plays a role in controlling cellular processes, such as cell cycle progression and regulation of development. The retinoblastoma proteinineracting zinc-finger gene (RIZ) is estrogen responsive and has two alternative promoters, the more downstream of which, promoter 2, is nearby to an EREsequence and is involved in estrogen receptor transcriptional activation. Methods: With the innovative DNA-Picked Chromatin (DPC) assay after timecourse of 17-ßestradiol (E2) induction of MCF-7 breast cancer cells, we highlight preferential interaction between hormone-responsive RIZ promoter and the polyadenylation sites. Gene expression analysis of induced cell RNA was performed with qRT-PCR assay. Results: Within 60’ of E2 treatment of cells, we have observed increased exon segments, exons 9a and 10 (alternative polyA site), linked to isolated promoter 2 and concomitant decrease of exon10 to RIZ promoter 1. The exon 9a shows a low association to RIZ promoter 1 without E2. qRT-PCR also demonstrated increased exon 9a-containing transcripts. Conclusions: The E2 remodels the chromatin architecture of PRDM2/RIZ gene locus to create a loop for the mRNA transcription with polyA-exon 9a, leading to the production of oncogenic variants.