VITELLOGENESIS AND THE REGULATION OF VITELLOGENIN GENE EXPRESSION IN THE SCALLOP.

(1)卵黄蛋白形成及卵黄原产生部位的激素调控。体内体外实验表明，卵黄原蛋白和总RNA含量的增加以及雌二醇-17β(E_2)和脑足神经节（CPG）提取物对卵黄蛋白形成的促进作用表明，卵巢可能是卵黄原蛋白和E_2的产生部位和CPG的热稳定因子。胰蛋白酶和凝乳胰蛋白酶抵抗和小于10,000的分子量促进调节卵黄形成。雌激素受体（estrogen receptor， ER）样免疫反应性仅在幼龄卵母细胞中出现，提示扇贝卵黄形成中存在自体合成系统，CPG可能在ER诱导的基础上促进e_2诱导卵黄形成。(2)卵黄原蛋白cDNA的克隆及基因表达调控。卵黄原蛋白cDNA克隆(克隆号：cSYP-1，接入号经northern blot分析，扇贝卵巢cDNA文库中的AB055960基因长度为12 ~ 13 kb，全长1698 bp，含有起始密码子和卵黄原蛋白mRNA。从cDNA序列推断出的氨基酸序列的同源性和分子系统发育树分析有力地支持该序列为卵黄原蛋白cDNA。卵黄原蛋白mRNA的表达在卵母细胞生长过程中有所增加，但在卵巢充满大量成熟卵母细胞的产卵季节仍保持不变。体外培养CPG对卵黄蛋白原mRNA水平无影响，与卵黄蛋白形成不同。由此得出以下初步结论：内源性雌激素通过内质网自合成诱导卵黄蛋白原进入卵母细胞，卵黄蛋白原被修饰并积累到卵母细胞中。CPG中一个促进e_2诱导的卵黄蛋白形成的因子同时促进卵黄蛋白原基因的转录和翻译。完全成熟的卵母细胞终止卵黄蛋白原mRNA的翻译，其半衰期似乎很长。少

(1) Hormonal regulation of yolk protein formation and producing site of vitellogeninThe increase in yolk protein and total RNA contents in the scallop ovary during oocyte growth and the promoting effect of estradiol-17β(E_2) and cerebral and pedal ganglion (CPG) extract on yolk protein formation in in vivo and in vitro experiment indicated that ovary should be a producing site of vitellogenin and E_2 and a factor in CPG which is heat stable, trypsin and chymotrypsin resist and less than 10,000 of molecular weight promotively regulate vitellogenesis. The founding of estrogen receptor (ER) like immuno-reactivity only in the young oocytes suggested the autosynthetic system in the scallop vitellogenesis and the possibility of the E_2-induced vitellogenesis promoted by CPG based on the ER induction.(2) Cloning of vitellogenin cDNA and regulation of vitellogenin gene expression.Cloned vitellogenin cDNA (clone No. cSYP-1, Accession No. AB055960) from cDNA library of scallop ovary was an incom … More plete length (1698 bp) with initiation codon and a actual vitellogenin mRNA was found to be 12-13 kb according to northern blot analysis. A homology and molecular phylogenic tree analysis of the amino acid sequence deduced from cDNA sequence strongly supported that the sequence was vitellogenin cDNA.The expression of vitellogenin mRNA increased during oocyte growth, but still kept the same level at spawning season when the ovary was full of many full grown oocyte. In vitro culture associated with CPG showed no influence on vitellogenin mRNA level, very unlike vitellogenesis.From these results, the following tentative conclusion is proposed Endogenous estrogen induces vitellogenin in the oocyte via ER autosynthetically and vitellogenin is modified and accumulated into the oocyte. A factor from CPG which promotes the E_2-induced vitellogenesis enhances the vitellogenin gene transcription and the translation at the same time. Full grown oocyte terminate translation of vitellogenin mRNA which appeared to be long half-life. Less