Nuclease sensitivity of the mouse HPRT gene promoter region: differential sensitivity on the active and inactive X chromosomes.
We investigated the conformation of the X-linked mouse hypoxanthine-guanine phosphoribosyltransferase gene (HPRT) promoter region both in chromatin from the active and inactive X chromosomes with DNase I and in naked supercoiled DNA with S1 nuclease. A direct comparison of the chromatin structures of the active and inactive mouse HPRT promoter regions was performed by simultaneous DNase I treatment of the active and inactive X chromosomes in the nucleus of interspecies hybrid cells from Mus musculus and Mus caroli. Using a restriction fragment length polymorphism to distinguish between the active and inactive HPRT promoters, we found a small but very distinct difference in the DNase I sensitivity of active versus inactive chromatin. We also observed a single DNase I-hypersensitive site in the immediate area of the promoter which was present only on the active X chromosome. Analysis of the promoter region by S1 nuclease digestion of supercoiled plasmid DNA showed an S1-sensitive site which maps adjacent to or within the DNase I-hypersensitive site found in chromatin but upstream of the region minimally required for normal HPRT gene expression.
Yang
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Institute for Molecular Genetics, Baylor College of Medicine, Houston, Texas 77030.
Caskey
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D000818:Animals; D002843:Chromatin / Q000502:physiology / Q000648:ultrastructure; D004278:DNA, Superhelical / Q000235:genetics; D003850:Deoxyribonuclease I; D004720:Endonucleases; D005796:Genes; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D008099:Liver / Q000201:enzymology; D008297:Male; D051379:Mice; D011401:Promoter Regions, Genetic; D015719:Single-Strand Specific DNA and RNA Endonucleases; D014960:X Chromosome
D002843:Chromatin; D004278:DNA, Superhelical; D007041:Hypoxanthine Phosphoribosyltransferase; D004720:Endonucleases; D003850:Deoxyribonuclease I; D015719:Single-Strand Specific DNA and RNA Endonucleases