Valdez B C, Henning D, Busch R K, Woods K, Flores-Rozas H, Hurwitz J, Perlaky L, Busch H
Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA.
Nucleic Acids Res. 1996 Apr 1;24(7):1220-4. doi: 10.1093/nar/24.7.1220.
Watermelon stomach is characterized by prominent stripes of ectatic vascular tissue in the stomach similar to stripes on a watermelon; in patients with this disorder chronic gastrointestinal bleeding occurs and approximately half of these patients have associated autoimmune disorders. In the serum of one patient, an antinucleolar antibody titer of 1:25 600 was found; the antibodies specifically recognized an approximately 100 kDa nucleolar protein, which we referred to as the 'Gu' protein. Its cDNA was cloned and sequenced. The Gu protein is a member of a new subgroup of RNA helicases, the DEXD box family. Gu protein fused with glutathione S-transferase contains ATP-dependent RNA helicase activity which preferably translocates in the 5'-->3' direction. Its RNA folding activity, RNA-dependent ATPase and dATPase activities, and its translocation direction are similar to those of RNA helicase II [Flores-Rozas, H. and Hurwitz, J. (1993) J. Biol. Chem. 268, 21372-21383]. Sequencing of 209 amino acids of RNA helicase II peptides showed 96.7% identity with the cDNA-derived amino acid sequence of the Gu protein. The precise biological roles of this RNA helicase in the biogenesis of ribosomal RNA and the pathogenesis of watermelon disease and autoimmune disorder require further study.
西瓜胃的特征是胃内出现明显的扩张血管组织条纹，类似于西瓜上的条纹；患有这种疾病的患者会发生慢性胃肠道出血，其中约一半患者伴有自身免疫性疾病。在一名患者的血清中，发现抗核仁抗体滴度为1:25600；这些抗体特异性识别一种约100 kDa的核仁蛋白，我们将其称为“Gu”蛋白。其cDNA被克隆并测序。Gu蛋白是RNA解旋酶新亚组DEXD盒家族的成员。与谷胱甘肽S-转移酶融合的Gu蛋白具有ATP依赖性RNA解旋酶活性，该活性优选沿5'→3'方向移位。其RNA折叠活性、RNA依赖性ATP酶和dATP酶活性以及其移位方向与RNA解旋酶II相似[Flores-Rozas, H.和Hurwitz, J. (1993) J. Biol. Chem. 268, 21372-21383]。对RNA解旋酶II肽的209个氨基酸进行测序，结果显示与Gu蛋白的cDNA推导氨基酸序列有96.7%的同一性。这种RNA解旋酶在核糖体RNA生物合成以及西瓜病和自身免疫性疾病发病机制中的精确生物学作用需要进一步研究。
