A regulatory region that 1) when located between a CRM and a gene's promoter prevents the CRM from modulating that genes expression and 2) acts as a chromatin boundary element or barrier that can block the encroachment of condensed chromatin from an adjacent region.
Comment:
moved from is_a: SO:0001055 transcriptional_cis_regulatory_region as per request from GREEKC initiative in August 2020.