An inactive X specific replication origin associated with a matrix attachment region in the human X linked HPRT gene.
Early in female mammalian embryogenesis, one of the two X chromosomes is inactivated to compensate the gene dosage between males and females. One of the features of X chromosome inactivation (XCI) is the late replication of the inactivated X chromosome. This study reports the identification, by competitive PCR of nascent DNA, of a replication origin in intron 2 of the human X-linked HPRT gene, that is functional only on the inactive X. Features frequently associated with replication origins, including a peak of enhanced DNA flexibility, a perfect match to the yeast ACS sequence, a 14/15 match to the Drosophila topoisomerase II consensus, and a 20/21 match to an initiation region consensus sequence, were identified close to the replication origin. The origin is located approximately 2 kb upstream of a matrix attachment region (MAR) and also contains two A:T-rich elements, thought to facilitate DNA unwinding.
Koina
Edda
E
Molecular Genetics Unit, Department of Cell and Molecular Biology, University of Technology, Sydney, NSW 2065, Australia. Koina@rsbs.anu.edu.au
Piper
Anita
A
D000818:Animals; D001483:Base Sequence; D041321:Chromosomes, Human, X; D006224:Cricetinae; D004247:DNA / Q000235:genetics; D017931:DNA Primers; D005260:Female; D006801:Humans; D006822:Hybrid Cells; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D008297:Male; D045170:Matrix Attachment Regions; D016133:Polymerase Chain Reaction; D018741:Replication Origin / Q000235:genetics*
D017931:DNA Primers; D004247:DNA; D007041:Hypoxanthine Phosphoribosyltransferase