LOCUS-CONTROL REGION FUNCTION AND HETEROCHROMATIN-INDUCED POSITION EFFECT VARIEGATION

Human CD2 locus control region (LCR) sequences are shown here to be es sential for establishing an open chromatin configuration. Transgenic m ice carrying an hCD2 minigene attached only to the 3' CD2 transcriptio nal enhancer exhibited variegated expression when the transgene integr ated in the centromere. In contrast, mice carrying a transgene with ad ditional 3' sequences showed no variegation even when the latter integ rated in centromeric positions. This result suggests that LCRs operate by ensuring an open chromatin configuration and that a short region, with no enhancer activity, functions in the establishment, maintenance , or both of an open chromatin domain.