DNA constructs useful in the production of thrombopoietin are disclosed. In general, the DNA constructs comprise a first DNA segment encoding a fusion of an amino-terminal secretory peptide joined to a thrombopoietin polypeptide and one or more additional DNA segments that provide for the transcription of the first segment. The secretory peptide is a native mammalian t-PA secretory peptide or may be modified to enhance proteolytic cleavage of the fusion. Also disclosed are cultured eukaryotic cells containing these DNA constructs and methods for producing thrombopoietin polypeptides through the use of the DNA constructs and cultured eukaryotic cells.