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 prope rties of the cloned chick beta-globin gene family when assembled into synthetic nuclei made by use of Xenopus egg extracts. Assembly in an e rythroid protein environment correctly recapitulates tissue-specific c hromatin structure and long-range promoter-enhancer interaction within the chromosomal locus, resulting in beta-globin gene activation. Nucl eosome-repressed beta-globin templates can be transcriptionally activa ted by double-stranded DNA replication in the presence of staged eryth roid proteins by remodeling of the chromatin structure within the prom oter region and establishment of distal promoter-enhancer communicatio n. The programmed transcriptional state of a gene, as encoded by its c hromatin structure and long-range promoter-enhancer interactions, is s table to nuclear decondensation and DNA replication unless active remo deling occurs in the presence of specific DNA-binding proteins.