Reynolds P J, Lesley J, Trotter J, Schulte R, Hyman R, Sefton B M
Salk Institute, San Diego, California 92138-9216.
Mol Cell Biol. 1990 Aug;10(8):4266-70. doi: 10.1128/mcb.10.8.4266-4270.1990.
The lck gene, which encodes the lymphoid cell-specific tyrosine protein kinase p56lck, is expressed from two widely separated promoters. The proximal promoter gives rise to a type I lck transcript, and the distal promoter gives rise to a type II transcript. We found that the ratio of the two transcripts changed during T-cell maturation. Type I lck mRNA was twofold more abundant than the type II transcript in early fetal thymocytes. In the adult, the type I and type II lck mRNAs were present in approximately equal amounts in immature thymocytes expressing the heat-stable antigen. In contrast, there was five- to ninefold more type II lck than type I lck mRNA in more mature thymocytes that did not express the heat-stable antigen and in splenic T cells. This change in relative transcript abundance probably reflects activation of the distal promoter and inactivation of the proximal promoter during T-cell maturation in the thymus. It is possible that the two promoters are regulated by different trans-acting factors whose expression is regulated during T-cell maturation.
lck基因编码淋巴样细胞特异性酪氨酸蛋白激酶p56lck，它由两个相距甚远的启动子表达。近端启动子产生I型lck转录本，远端启动子产生II型转录本。我们发现，在T细胞成熟过程中，这两种转录本的比例发生了变化。在早期胎儿胸腺细胞中，I型lck mRNA的丰度比II型转录本高两倍。在成年期，在表达热稳定抗原的未成熟胸腺细胞中，I型和II型lck mRNA的含量大致相等。相反，在不表达热稳定抗原的更成熟胸腺细胞和脾T细胞中，II型lck mRNA比I型lck mRNA多5至9倍。相对转录本丰度的这种变化可能反映了胸腺中T细胞成熟过程中远端启动子的激活和近端启动子的失活。这两个启动子可能受不同的反式作用因子调控，这些因子的表达在T细胞成熟过程中受到调控。
