High-resolution methylation analysis of the human hypoxanthine phosphoribosyltransferase gene 5{prime} region on the active and inactive X chromosomes: Correlation with binding sites for transcription factors

Journal Article · Tue Feb 01 04:00:00 EST 1994 · Molecular and Cellular Biology

DOI:https://doi.org/10.1128/MCB.14.2.1419· OSTI ID:577145

Hornstra, I K; Yang, T P ^[1]

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1. Univ. of Florida College of Medicine, Gainesville, FL (United States)

DNA methylation within GC-rich promoters of constitutively expressed X-linked genes is correlated with transcriptional silencing on the inactive X chromosome in female mammals. For most X-linked genes, X chromosome inactivation results in transcriptionally active and inactive alleles occupying each female nucleus. To examine mechanisms responsible for maintaining this unique system of differential gene expression, we have analyzed the methylation of individual cytosine residues in the 5{prime} CpG island of the human hypoxanthine phosphoribosyltransferase (HPRT) gene on the active and inactive X chromosomes. These studies demonstrate the 5{prime} CpG islands of active and 5-azacytidine-reactivated alleles are essentially unmethylated while the inactive allele is hypermethylated. The inactive allele is completely methylated at nearly all CpG dinucleotides except in a 68-bp region containing four adjacent GC boxes where most CpG dinucleotides are either unmethylated or partially methylated. Curiously, these GC boxes exhibit in vivo footprints only on the active X chromosome, not on the inactive X. The methylation pattern of the inactive HPRT gene is strikingly different from that reported for the inactive X-linked human phosphoglycerate kinase gene which exhibits methylation at all CpG sites in the 5{prime} CpG island. These results suggest that the position of methylated CpG dinucleotides, the density of methylated CpGs, the length of methylated regions, and/or chromatin structure associated with methylated DNA may have a role in repressing the activity of housekeeping promoters on the inactive X chromosome. The pattern of DNA methylation on the inactive human HPRT gene may also provide insight into the process of inactivating the gene early in female embryogenesis. 55 refs., 7 figs.

• Sponsoring Organization: USDOE
• OSTI ID: 577145
• Journal Information: Molecular and Cellular Biology, Journal Name: Molecular and Cellular Biology Journal Issue: 2 Vol. 14; ISSN 0270-7306; ISSN MCEBD4
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
CHROMATIN
CYTOSINE
DENSITY
DNA
DNA SEQUENCING
FEMALES
GENE REGULATION
GENE REPRESSORS
GENES
GENETIC MAPPING
HUMAN X CHROMOSOME
HYPOXANTHINE PHOSPHORIBOSYLTRANSFERASE
LENGTH
METHYLATION
NUCLEOTIDES
ONTOGENESIS
POLYMERASE CHAIN REACTION
RESOLUTION
STRUCTURE-ACTIVITY RELATIONSHIPS
TRANSCRIPTION FACTORS