Strategy used to clone human Jak2. A combination of library screening using the mouse Jak2 cDNA as a probe and RT-PCR was used to obtain the full-length cDNA of human Jak2. The screening yielded a series of overlapping fragments combining to form a 1.8-kb ORF (nucleotides 1398 to 3207). A RT-PCR with primers to the published murine sequence and to the 1.8-kb ORF obtained from the library screening was used to complete the cloning of the 5′ (nucleotides 1 to 1416) and 3′ (nucleotides 3055 to 3503) ends of the human Jak2. A stop codon was found in position 3402, as indicated by the arrow.