Masibay A S, Damewood G P, Boeggeman E, Qasba P K
Laboratory of Mathematical Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Biochim Biophys Acta. 1991 Oct 8;1090(2):230-4. doi: 10.1016/0167-4781(91)90106-v.
The beta-1,4-galactosyltransferase (GT; EC 2.4.1.90) is localized in the trans-cisternae of the Golgi apparatus where it catalyzes the transfer of galactose from UDP-galactose to the N-acetylglucosamine residue of secretory and membrane-bound glycoproteins. Given the potential role of GT in cell-cell interaction and the fact that numerous cell surface events occur during cell growth we studied the possible relationship between GT expression and 3T3 cell growth. The level of GT mRNA increases 3--4-fold 2 h after serum-stimulation of quiescent 3T3 cells. Protein biosynthesis inhibitors like cycloheximide and anisomycin superinduce GT mRNA expression. Concomitant with this increase is an observed rise in the level of GT protein as well as an increase in overall GT enzymatic activity. Antibody-binding studies and direct enzyme assays of intact cells, along with subcellular fractionation experiments indicate that there is an increase in both Golgi and cell surface-associated GT pools upon serum-stimulation of resting cells. We conclude that GT is a member of the cell-cycle dependent genes whose expression is growth regulated.
β-1,4-半乳糖基转移酶（GT；EC 2.4.1.90）定位于高尔基体的反式扁平囊，在那里它催化半乳糖从尿苷二磷酸半乳糖转移至分泌型和膜结合型糖蛋白的N-乙酰葡糖胺残基上。鉴于GT在细胞间相互作用中的潜在作用，以及在细胞生长过程中会发生众多细胞表面事件，我们研究了GT表达与3T3细胞生长之间的可能关系。静止的3T3细胞经血清刺激2小时后，GT mRNA水平增加3至4倍。蛋白质生物合成抑制剂如环己酰亚胺和茴香霉素可超诱导GT mRNA表达。与此增加相伴的是，观察到GT蛋白水平升高以及GT总体酶活性增加。完整细胞的抗体结合研究和直接酶测定，以及亚细胞分级分离实验表明，静止细胞经血清刺激后，高尔基体和细胞表面相关的GT库均增加。我们得出结论，GT是细胞周期依赖性基因的成员，其表达受生长调节。
