Molecular cloning of cDNA encoding 20 kDa variant human growth hormone and the alternative splicing mechanism

cDNA encoding the 20 kDa variant form of human growth hormone has been cloned, and its sequence analysis verified the alternative splicing mechanism for the mRNA synthesis. The cDNA sequence lacked 45 nucleotides corresponding to the sequence of 15 amino acids in the 22 kDa form of growth hormone. The cDNA clones for the 20 kDa variant hormone had the homogeneous 5'-ends, while the clones for the 22 kDa form showed a minor heterogenity, having two transcription initiation sites. The percentage of 20 kDa variant cDNA clones was approx. 7.7% of the total human growth hormone cDNA clones, consistent with the contents of 20 kDa hormone protein in human anterior pituitary and plasma.