MARs mission update.

Genes are organized as chromatin domains and positioned in the nucleus through regions of nuclear matrix association, termed MARs. Although well-studied, the mechanisms regulating expression of the beta-globin locus remain an enigma. Here, we show that certain MAR sequences of the beta-globin locus are conserved and reiterated throughout the genome in association with other genes of the hematopoietic lineage. Further, the density of the MARs within the beta-globin locus and the sharing of these sequences by the various members of this gene cluster suggest that they may provide critical gene regulatory components.