REGULATED EXPRESSION OF THE BETA-GLOBIN GENE LOCUS IN SYNTHETIC NUCLEI

Regulated gene expression within a complex chromosomal locus requires multiple nuclear processes. We have analyzed the transcriptional properties of the cloned chick beta-globin gene family when assembled into synthetic nuclei made by use of Xenopus egg extracts. Assembly in an erythroid protein environment correctly recapitulates tissue-specific chromatin structure and long-range promoter-enhancer interaction within the chromosomal locus, resulting in beta-globin gene activation. Nucleosome-repressed beta-globin templates can be transcriptionally activated by double-stranded DNA replication in the presence of staged erythroid proteins by remodeling of the chromatin structure within the promoter region and establishment of distal promoter-enhancer communication. The programmed transcriptional state of a gene, as encoded by its chromatin structure and long-range promoter-enhancer interactions, is stable to nuclear decondensation and DNA replication unless active remodeling occurs in the presence of specific DNA-binding proteins.