Debrand E, Heard E, Avner P
Unité de Génétique Moléculaire Murine, CNRS URA 1968, Institut Pasteur, Paris, France.
Genomics. 1998 Mar 15;48(3):296-303. doi: 10.1006/geno.1997.5173.
The overall organization of the X-inactivation center (XIC/Xic) candidate region seems poorly conserved between human and mouse. The orientation of a region containing the X-inactive-specific transcript (Xist/ XIST) gene and three genes located 3' of Xist/XIST has been shown to be inverted between the two species, although the actual extent of this rearrangement is unknown. We have cloned and mapped the mouse homolog of the human XPCT (X-linked PEST-containing transporter) gene, which encodes a putative transmembrane transporter. Human XPCT is located about 200 kb outside of the XIC candidate region and 600 kb 5' of or telomeric to the XIST gene. The mouse Xpct gene, which lies approximately 300 kb 5' of and centromeric to Xist, displays 85% identity at the nucleotide level with the human gene, and the overall protein structure is conserved. The transcriptional orientation of mouse Xpct with respect to Xist is the opposite of that in human. Consequently, the evolution of the region between human and mouse appears to be highly complex, with structural rearrangements involving a region of up to 600 kb or more around the Xist gene.
X染色体失活中心（XIC/Xic）候选区域的整体组织在人类和小鼠之间似乎保守性很差。包含X染色体失活特异性转录本（Xist/XIST）基因以及位于Xist/XIST基因3'端的三个基因的区域，在这两个物种之间的方向已被证明是相反的，尽管这种重排的实际范围尚不清楚。我们已经克隆并定位了人类XPCT（X连锁含PEST转运蛋白）基因的小鼠同源基因，该基因编码一种假定的跨膜转运蛋白。人类XPCT位于XIC候选区域外约200 kb处，且在XIST基因的5'端600 kb处或端粒方向。小鼠Xpct基因位于Xist基因5'端约300 kb处且在着丝粒方向，在核苷酸水平上与人类基因有85%的同一性，并且整体蛋白质结构是保守的。小鼠Xpct相对于Xist的转录方向与人类相反。因此，人类和小鼠之间该区域的进化似乎高度复杂，涉及Xist基因周围长达600 kb或更多区域的结构重排。
