新的生长激素异形体基因的发现及全长cDNA的克隆

Detection and Cloning of the Full-length cDNA of a New Growth Hormone Isoform

在通过大规模 ESTS技术对垂体基因表达谱的研究中 ,从垂体组织产生了 72 2 2个 ESTS,有385个 ESTs是代表生长激素 (GH)基因的 ,其中 1个为中间缺失 1 38bp的 GH异形体基因 ,并经巢式 RT- PCR及测序证实 ;该基因编码 1 71个氨基酸的前肽 ,去除信号肽后 ,其成熟肽由 1 45个氨基酸组成 ;经生物信息学处理 ,其分子量大小约 1 7k D;与正常生长激素分子内有 2个 GH受体结合位点不同 ,该新的 GH异形体分子内仅有一个生长激素受体的结合位点 .研究结果揭示 :正常垂体内存在着新的 GH异形体基因 ,该基因可能编码外周血中 1 6k D的生长激素 ;其功能可能为 2 2k D GH的生理拮挤剂 .

In the study on the human normal pituitary gene expression profile by producing large scale expressed sequence tags(EST S),7222 EST S were produced from human normal pituitary cDNA library.Growth hormone gene was represented by 385 EST S,of which one represented a new GH isoform in which 138 base pairs (bp) were deleted,and was confirmed by nested reverse transcription polymerase chain reaction (nested RT PCR) and sequencing.It encoded a pre peptide of 171 amino acids.After removal of the signal peptide,the matured peptide comprised 145 amino acids.The molecular weight of the matured peptide was predicted as about 17 kD by means of bioinformatics.The new GH isoform differed from classical growth hormone which had 2 GH receptor binding sites,and there was only one GH receptor binding site in the new GH isoform molecule.The results suggested that a new GH isoform was expressed in normal human pituitary gland.It probably encoded the 16 kD GH which was previously found in peripheral blood.It may be a physiological antagonist of the 22 kD GH.