Department of Biochemistry and Molecular Biology, UMDNJ-New Jersey Medical School, 185 South Orange Ave., Newark, NJ 07101-1709, USA.
Mol Cell Biol. 2011 Jan;31(2):287-99. doi: 10.1128/MCB.00603-10. Epub 2010 Nov 15.
Human chorionic gonadotropin (hCG) is a glycoprotein hormone essential to pregnancy. hCG is heterodimeric and functionally defined by its β subunit. hCGβ evolved from the β subunit of luteinizing hormone in two phases. In the first phase, type I genes (hCGβ3, -5, -7, and -8) acquired changes affecting gene expression and extending the proteins' C terminus. In the second phase, type II genes (hCGβ1 and -2) were formed by the insertion of a DNA element into the type I 5' end. The insertion includes the small noncoding RNA gene snaR-G and has been predicted to drastically change the protein products encoded. We trace the insertion to the common ancestor of the African great apes and show that it contains transcription signals, including snaR-G. Type II transcripts are predominantly expressed in testis. Contrary to predictions, the product of the major mRNA splice form is hCGβ. A novel peptide is encoded by alternatively spliced transcripts. These findings support the view that type II genes evolved in African great apes to function in the male reproductive system.
人绒毛膜促性腺激素（hCG）是一种糖蛋白激素，对妊娠至关重要。hCG 是二聚体，其功能由其β亚基定义。hCGβ 由黄体生成素的β亚基分两个阶段进化而来。在第一阶段，I 型基因（hCGβ3、-5、-7 和-8）获得了影响基因表达并延长蛋白质 C 末端的变化。在第二阶段，通过将 DNA 元件插入 I 型 5'端形成 II 型基因（hCGβ1 和 -2）。该插入包括小非编码 RNA 基因 snaR-G，并已预测其会极大地改变编码的蛋白质产物。我们追踪到该插入源自非洲大猿的共同祖先，并表明它包含转录信号，包括 snaR-G。II 型转录本主要在睾丸中表达。与预测相反，主要 mRNA 剪接形式的产物是 hCGβ。选择性剪接转录本编码一种新的肽。这些发现支持了这样一种观点，即 II 型基因在非洲大猿中进化，以在男性生殖系统中发挥作用。
