The chromosomal gene structure and two mRNAs for human granulocyte colony-stimulating factor.

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Abstract
Two different cDNAs for human granulocyte colony‐stimulating factor (G‐CSF) were isolated from a cDNA library constructed with mRNA prepared from human squamous carcinoma cells, which produce G‐CSF constitutively. The nucleotide sequence analysis of both cDNAs indicated that two polypeptides coded by these cDNAs are different at one position where three amino acids are deleted/inserted. When the two cDNAs were introduced into monkey COS cells under the SV40 early promoter, both of them produced proteins having authentic G‐CSF activity and some difference in the specific activity was suggested. A human gene library was then screened with the G‐CSF cDNA and the DNA fragment containing the G‐CSF chromosomal gene was characterized by the nucleotide sequence analysis. The human G‐CSF gene is interrupted by four introns and a comparison of the structures of the two G‐CSF cDNAs with that of the chromosomal gene indicated that the two mRNAs are generated by alternative use of two 5′ splice donor sequences in the second intron of the G‐CSF gene. When the G‐CSF chromosomal gene was expressed in monkey COS cells by using the SV40 enhancer two mRNAs were detected by S1 mapping analysis.