The complete gene for human thrombopoietin (TPO) has been cloned by sc
reening a human genomic library using human TPO cDNA as a probe. This
gene is 6.2 kb in length and contains six exons and five introns. It i
s shown that the human genome contains a single copy of the human TPO
gene according to Southern blotting analysis. The transcription initia
tion site was determined by S1 nuclease mapping. The human TPO gene ex
pressed TPO activity when transfected into COS-1 cells. The human TPO
gene has been mapped to chromosome 3q27 by in situ hybridization using
a biotin-labeled probe.