We have determined the complete sequence of the human growth hormone (hGH) gene and the position of the mature 5' end of the hGH mRNA within the sequence. Comparison of this sequence with that of a cloned hGH cDNA shows that the gene is interrupted by four intervening sequences. S1 mapping shows that one of these intervening sequences has two different 3' splice sites. These alternate splicing pathways generate hGH peptides of different sizes which are found in normal pituitaries. Comparison of sequences near the 5' end of the hGH mRNA with a similar region of the alpha subunit of the human glycoprotein hormones reveals an unexpected region of homology between these otherwise unrelated peptide hormones.
A 2.6-kilobase (kb) EcoRI restriction endonuclease fragment containing human growth hormone (hGH; somatotropin) gene sequences and a 2.8-kb EcoRI fragment containing human chorionic somatomammotropin (hCS; choriomammotropin) gene sequences have been identified by hybridization to cloned cDNA. Human DNA was cleaved with EcoRI and fractionated by preparative agarose gel electrophoresis; DNA in the size range 2-3 kb was ligated to Xgt WES'XB DNA and viable recombinant bacteriophage were recovered by in vitro packaging. After infection of Escherichia coli and screening of phage plaques, single isolates of hGH and hCS gene sequences were obtained. Restriction endonuclease mapping showed that the hGH gene contains three intervening sequences interrupting the coding sequence. Partial DNA sequence analysis of the hGH gene, obtained by the chain termination method, confirmed the location of the intervening sequences and the identity of the fragment. Human growth hormone (hGH) and human chorionic somatomammotropin (hCS) are two closely related polypeptide hormones which have more than 80% of their 191 amino acids in common (1, 2). They have different biological activities and are synthesized in different tissues: hGH in the pituitary and hCS in the placenta. The genes coding for these two hormones provide a good system for studying the organization of structurally related sequences and their tissue-specific expression.A 550-base-pair Hae III fragment cDNA clone coding for amino acids 24-191 of the hCS sequence has been described (3). Recently, the analogous 550-base-pair Hae III fragment coding for hGH has also been cloned and its nucleotide sequence has been determined (unpublished data). The nucleotide sequences of these two fragments are 93% homologous.Further analysis of this system requires the isolation of genomic DNA fragments that contain the entire coding sequences and the regulating elements that may be involved in the differential expression of the genes. This report describes the construction of genomic DNA clones for sequences of both the hGH and hCS genes by utilizing bacteriophage Xgt WES-XB as the vector (4) and the bacteriophage X in vitro packaging system of Blattner et al. (5). MATERIALS AND METHODSHuman Placental DNA. High molecular weight DNA was extracted from human placenta obtained by caesarian section. The frozen tissue was dispersed in a blender, treated with proteinase K, extracted with phenol/chloroform, and then incubated sequentially with RNase A and proteinase K (6). After extraction with phenol/chloroform, the DNA was precipitated with ethanol.Preparative Agarose Gel Electrophoresis. EcoRI-digested human placental DNA (17.5 mg) was fractionated on a continuous elution, horizontal, 0.8% agarose gel, essentially as described by Polsky et al. (6) except that Seakem HGT (P) agarose was used because this appeared to contain fewer contaminants that inhibit subsequent enzymatic steps. The DNA was collected in approximately 80 fractions, and aliquots of these were assayed by analytical aga...
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