Replication timing of the human X-inactivation center (XIC) region: correlation with chromosome bands.
The human genome is composed of long-range G+C% mosaic structures, which are thought to be related to chromosome bands. Replication timing during S phase is associated with chromosomal band zones; thus, band boundaries are thought to correspond to regions where replication timing switches. The proximal limit of the human X-inactivation center (XIC) has been localized cytologically to the junction zone between Xq13.1 and Xq13.2. Using PCR-based quantification of the newly replicated DNA from cell-cycle fractionated THP-1 cells, the replication timing in and around the XIC was determined at the genome sequence level. We found two regions where replication timing changes from the early to late period during S phase. One is located near a large inverted duplication proximal to the XIC, and the other is near the XIST locus. We propose that the 1Mb late-replicated zone (from the large inverted duplication to XIST) corresponds to a G-band Xq13.2. Several common characteristics were observed in the XIST region and the MHC class II-III junction which was previously defined as a band boundary. These characteristics included differential high-density clustering of Alu and LINE repeats, and the presence of polypurine/polypyrimidine tracts, MER41A, MER57 and MER58B.
Watanabe
Y
Y
Division of Evolutionary Genetics, Department of Population Genetics, National Institute of Genetics, Yata 1111, Mishima, 411-8540, Shizuoka-ken, Japan.
Tenzen
T
T
Nagasaka
Y
Y
Inoko
H
H
Ikemura
T
T
D000818:Animals; D016466:CHO Cells; D002453:Cell Cycle; D002871:Chromosome Banding; D006224:Cricetinae; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004303:Dosage Compensation, Genetic; D006801:Humans; D008285:Major Histocompatibility Complex / Q000235:genetics; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics; D014407:Tumor Cells, Cultured; D014960:X Chromosome / Q000235:genetics*
D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D014157:Transcription Factors; C077885:XIST non-coding RNA; D004247:DNA