A Family of Homologous X Chromosomal Sequences with Some Members Showing Evidence of Enhancer Activity

摘要

ABSTRACTLittle is known about either the frequency of occurrence of enhancers or the interrelationships of various enhancers in mammalian genomes. Previous reports described a potent, transcriptional enhancer within the sequence termed "Xrep," a human X chromosomal genomic clone (Rileyet al.,1986; Riley, 1989a). Additional Xrep-related sequences reside on the human X chromosome. A probe for the Xrep enhancer hybridized with multiple restriction fragments located on the X chromosome. Two of the fragments cross-hybridizing with the enhancer had identical enhancer-like sequences but dissimilar flanking sequences. However, both of the sequenced enhancers were flanked by poly(GT) repeats strongly implicated in the generation of polymorphisms. A third sequence cross-hybridizing to the enhancer probe was found, in chromatin form, to be extremely DNase I hypersensitive.