Cloning of the bovine interleukin-3-encoding cDNA.

Interleukin-3 (IL-3) is one of the cytokines that act during the early and late stages of blood cell formation. To enable the study of the role of IL-3 in bovine haemopoietic stem cell differentiation, the polymerase chain reaction was used to amplify an IL-3 cDNA from first-strand cDNAs prepared from RNA isolated from 4- and 5-hour concanavalin-A-stimulated peripheral blood lymphocytes (PBL) from N'Dama cattle. An analysis of the cDNA sequence reveals that it contains a 432-nucleotide (nt) open reading frame which codes for 144 amino acids (aa). Cleavage of the putative signal peptide consisting of the first 17 aa yields the mature form of the protein (14.5 kDa). Comparisons of the bovine IL-3 sequence with the sheep, human and mouse IL-3 sequences show that the bovine sequence shares 90.7, 55.8 and 51.9% nt identity, respectively, in the coding region, and 85.4, 35 and 27.7% aa identity, respectively.