The XIST locus replicates late on the active X, and earlier on the inactive X based on FISH DNA replication analysis of somatic cell hybrids.

Autor: Torchia BS; Center for Medical Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-3914, USA., Migeon BR
Jazyk: angličtina
Zdroj: Somatic cell and molecular genetics [Somat Cell Mol Genet] 1995 Sep; Vol. 21 (5), pp. 327-33.
DOI: 10.1007/BF02257467
Abstrakt: We have recently reported results of DNA replication analysis of three X-linked loci (FRAXA, F8C and XIST) on the X chromosomes in male and female fibroblasts using fluorescence in situ hybridization (FISH) (1). Although our findings that XIST replicates later on the active X than on the inactive X are similar to those of Boggs & Chinault (2) based on a FISH assay in female lymphoblasts, they are the opposite of observations recently reported by Hansen et al. (3) using a different technique. Because our conclusions about the inactive X were deduced from the behavior of the active X in male cells, we reexamined the time when these loci replicate on the human inactive X chromosome isolated from its homolog in somatic cell hybrids. We also studied the same chromosome as an active X in related hybrids. The results provide direct evidence that the expressed XIST locus on the inactive X replicates earlier than its repressed homolog on the active X and earlier than the FRAXA locus which is repressed on this chromosome. The silent XIST locus on the active X replicates late along with F8C which is also not transcribed in these cells. Possible reasons for the different results obtained by Hansen et al. (3) are discussed.
Databáze: MEDLINE
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