Isolation and identification of the gene induced by Ets family transcription factor PU.1 in murine erythroleukemia cells

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PU.1, a hematopoitic cell-specific Ets family transcription factor, is involved in the generation of marine erythroleukemia (MEL). We previously reported that overexpression of PU.1 inhibits erythroid differentiation in MEL cells. To identify the target gene(s) of PU.1 in MEL cells, we carried out differential display (DD) analysis and subsequently isolated a novel gene whose expression was up-regulated in MEL cells after overexpression of PU.1. Because an 1.1 kb of open reading frame near the 5' end of the 8kb of transcript of the gene exhibited about 90% homology with the human calcium-calmodulin-dependent kinase I-like kinase (CKLiK) gene, which has been, reported to be predominantly expressed in granulocytes, it was identified as a mouse homologue of human CKLiK gene. The mouse CKLiK (mCKLiK) gene was mapped, to the mouse chromosome 2A1-A3 region, and shown to be expressed predominantly in T cells and embryonal carcinoma cells. Two types of transcripts were present showing a difference in the 3' portion of the coding region. overexpression of each isoform of mCKLiK in MEL cells revealed that one of them induces, while the other inhibits, apoptosis under low serum condition. Inhibition of erythroid-differentiation which were previously observed by us after overexpression of PU.1 in MEL cells, however, were not provoked in the cells overexpressing mCKLiK. These results suggest that mCKLiK is up-regulated by overexpression of PU.1 in MEL cells and involved in apoptosis of the cells.