Although HERV-HX may be the same X-linked HERV-H
IU1 inhibitor that has been reported to be frequently up-regulated in colon tumor samples by two other independent groups [15] and [16], we are first to identify and characterize its full-length transcript. There are several other HERV-H elements on X chromosome [17]. There is another HERV-H located on Xp22. We were unable to detect transcription of this HERV-H element in colon tumor or normal tissues by RT-PCR (results not shown). The genes that are nearest to HERV-HX are NLGN4X about 1.34 Mb upstream and PRKX about 0.83 Mb downstream. NLGN4X belongs to the neuronal cell surface protein family and may be involved in the formation and remodeling of central nervous system synapses, and PRKX is involved in melanogenesis. There is no known association between NLGN4X or PRKX and colon cancer. However, it is hard to predict whether
expression of HERV-HX could interfere with the expression of other somatic genes, because one gene may have transcriptional interference effect on another that is at a great distance [18].
