Structure and chromosomal localization of the human glycogenin-2 gene GYG2

Glycogenin-2 is one of two self-glucosylating proteins involved in the init iation phase of the synthesis of the storage polysaccharide glycogen. Cloni ng of the human glycogenin-2 gene, GYG2, has revealed the presence of 11 ex ons and a gene of more than 46 kb in size. The structure of the gene explai ns much of the observed diversity in glycogenin-2 cDNA sequences as being d ue to alternate exon usage. In some cases, then is variation in the splice junctions used. Over regions of protein sequence similarity, the GYG2 gene structure is similar to that of the other glycogenin gene, GYG. A genomic G YG2 clone was used to localize the gene to Xp22.3 by fluorescence in-situ h ybridization. Localization close to the telomere of the short arm of the X chromosome is consistent with mapping information obtained from glycogenin- 2 STS sequences. Glycogenin-2 maps between the microsatellite anchor marker s AFM319te9 (DXS7100) and AFM205tf2 (DXS1060), and its 3' end is 34.5 kb fr om the 3' end of the arylsulphatase gene ARSD. GYG2 is outside the pseudoau tosomal region PAR1 but still in a region of X-Y shared genes. As is true f or several other genes in this location, an inactive remnant of GYG2, consi sting of exons 1-3, may be present on the Y chromosome. (C) 2000 Elsevier S cience B.V. All rights reserved.