Wong E A, Silsby J L, el Halawani M E
Department of Animal Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306.
DNA Cell Biol. 1992 Nov;11(9):651-60. doi: 10.1089/dna.1992.11.651.
The transition from egg laying to incubation activity in birds is associated with a dramatic rise in serum prolactin levels. To further our understanding of the regulation of prolactin gene expression in birds, a cDNA clone encoding turkey Pit-1/GHF-1 was isolated. The turkey cDNA, designated tPit-1/GHF-1, was 1,123 nucleotides in length and encoded a protein of 327 amino acids, including a conserved 80-amino-acid POU-specific domain and a 60-amino-acid POU homeodomain. tPit-1/GHF-1 POU-specific domain and POU-homeodomain showed 94-95% amino acid identity with the corresponding rat Pit-1/GHF-1 domains. At its amino terminus, tPit-1/GHF-1 contained a 26-amino-acid insertion comparable to that found in the rat variant isoform, Pit-1 beta. Two other insertions of 38 and 7 amino acids were present and were not found in the mammalian protein. Levels of tPit-1/GHF-1 mRNA in pituitary tissue were examined at different phases of the turkey reproductive cycle by Northern blotting. tPit-1/GHF-1 mRNA was expressed as a 3.5-kb transcript, whose abundance remained relatively constant throughout the reproductive cycle. Thus, the dramatic rise in prolactin mRNA, observed during hyperprolactinemia in incubating turkey hens, was not associated with a concomitant increase in tPit-1/GHF-1 gene expression.
鸟类从产卵到开始孵化活动的转变与血清催乳素水平的急剧上升有关。为了进一步了解鸟类催乳素基因表达的调控机制，我们分离出了一个编码火鸡Pit-1/GHF-1的cDNA克隆。这个火鸡cDNA，命名为tPit-1/GHF-1，长度为1123个核苷酸，编码一个由327个氨基酸组成的蛋白质，其中包括一个保守的80个氨基酸的POU特异性结构域和一个60个氨基酸的POU同源结构域。tPit-1/GHF-1的POU特异性结构域和POU同源结构域与相应的大鼠Pit-1/GHF-1结构域的氨基酸序列一致性为94%-95%。在其氨基末端，tPit-1/GHF-1含有一个26个氨基酸的插入序列，类似于在大鼠变异同工型Pit-1β中发现的插入序列。另外还存在两个分别为38个和7个氨基酸的插入序列，这在哺乳动物蛋白中未发现。通过Northern印迹法检测了火鸡生殖周期不同阶段垂体组织中tPit-1/GHF-1 mRNA的水平。tPit-1/GHF-1 mRNA以一个3.5 kb的转录本形式表达，其丰度在整个生殖周期中相对保持恒定。因此，在孵化期火鸡母鸡高催乳素血症期间观察到的催乳素mRNA的急剧上升，与tPit-1/GHF-1基因表达的相应增加无关。
