Linzer D I, Lee S J, Ogren L, Talamantes F, Nathans D
Proc Natl Acad Sci U S A. 1985 Jul;82(13):4356-9. doi: 10.1073/pnas.82.13.4356.
Proliferin is a recently described, prolactin-related protein whose mRNA appears in several murine cell lines during active growth. We have surveyed a number of mouse organs or tissues for the presence of mRNAs that hybridize to cloned proliferin cDNA. Of the tissues tested, only the placenta yielded proliferin-related mRNA. This placental RNA is about 1 kilobase in length, increases sharply between days 8 and 10 of pregnancy, and then gradually declines through day 18. It is more abundant in RNA extracted from the fetal, compared to the maternal, part of the placenta. From a cDNA plasmid library prepared from poly(A)+ placental RNA, two types of proliferin-related clones were isolated, differing in intensity of hybridization to proliferin cDNA. By nucleotide sequence analysis, a strongly hybridizing clone was found to be nearly identical to the proliferin cDNA clone isolated from a library prepared from mRNA of a growing mouse fibroblastic cell line. Using an antiserum prepared against a synthetic proliferin fusion protein, we show that proliferin is secreted as a glycoprotein by minced placental tissue and that it differs from mouse placental lactogen. We conclude that proliferin is a placental hormone that is synthesized in certain mouse cell lines during active growth. Its function during pregnancy and during the growth of cultured cells is presently unknown.
增殖蛋白是一种最近被描述的、与催乳素相关的蛋白质，其信使核糖核酸（mRNA）在活跃生长期间出现在几种小鼠细胞系中。我们已经在许多小鼠器官或组织中检测了与克隆的增殖蛋白互补脱氧核糖核酸（cDNA）杂交的mRNA的存在情况。在所测试的组织中，只有胎盘产生了与增殖蛋白相关的mRNA。这种胎盘RNA长度约为1千碱基，在怀孕第8天至第10天之间急剧增加，然后在第18天逐渐下降。与胎盘母体部分提取的RNA相比，从胎盘胎儿部分提取的RNA中这种RNA更为丰富。从由聚腺苷酸加（poly(A)+）胎盘RNA制备的cDNA质粒文库中，分离出了两种与增殖蛋白相关的克隆，它们与增殖蛋白cDNA的杂交强度不同。通过核苷酸序列分析，发现一个强杂交克隆与从一个由生长中的小鼠成纤维细胞系mRNA制备的文库中分离出的增殖蛋白cDNA克隆几乎相同。使用针对合成增殖蛋白融合蛋白制备的抗血清，我们表明增殖蛋白由切碎的胎盘组织作为糖蛋白分泌，并且它与小鼠胎盘催乳素不同。我们得出结论，增殖蛋白是一种胎盘激素，在活跃生长期间在某些小鼠细胞系中合成。其在怀孕和培养细胞生长过程中的功能目前尚不清楚。
