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

PU.1是一种造血细胞特异性ETS家族转录因子，参与了海洋红白血病(MEL)的发生。我们先前报道过PU1的过表达抑制MEL细胞的红系分化。为了在MEL细胞中鉴定PU1的靶基因(S)，我们进行了差异显示(DD)分析，并随后克隆了PU1过表达后在MEL细胞中表达上调的新基因。由于该基因8kb转录本5‘端有一个1.1kb的开放阅读框，与已报道主要在粒细胞中表达的人钙调素依赖的类钙调蛋白激酶(CKLiK)基因有90%的同源性，因此该基因被鉴定为人CKLiK基因的小鼠同源基因。将小鼠CKLiK(MCKLiK)基因定位于小鼠染色体2A1-A3区域，发现其主要在T细胞和胚胎癌细胞中表达。存在两种类型的转录本，显示编码区的3‘部分存在差异。MCKLiK各亚型在MEL细胞中的过表达表明，在低血清条件下，其中一种亚型诱导细胞凋亡，而另一种亚型则抑制细胞凋亡。然而，我们先前在MEL细胞中过表达PU.1后观察到的红系分化抑制，在过表达mCKLiK的细胞中没有引起。这些结果提示mCKLiK在MEL细胞中通过PU1的过表达而上调，并参与细胞的凋亡。

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.