Williams M, Maizels N
Department of Molecular Biophysics and Biochemistry, Yale Medical School, New Haven, Connecticut 06510.
Genes Dev. 1991 Dec;5(12A):2353-61. doi: 10.1101/gad.5.12a.2353.
In nuclear extracts of primary murine B lymphocytes cultured with LPS we have identified an inducible DNA-binding activity that is a candidate regulator of isotype-switch recombination. This LPS-responsive factor, which we refer to as LR1, is induced in LPS-cultured primary cells with kinetics that parallel isotype-switch recombination. LR1 binds sequences from the S gamma 1, S gamma 3, and S alpha switch regions, as well as the heavy-chain enhancer, and these binding sites define a consensus that occurs in each of the murine switch regions. LR1 activity is present in pre-B and B-cell lines but absent from primary B cells that have not been cultured with mitogen and from highly differentiated B-cell lines. LR1-binding activity depends on phosphorylation and is lost following incubation of nuclear extracts with acid phosphatase. The LPS inducibility and phosphorylation dependence of LR1 activity suggest that this factor monitors kinase-dependent events in cell development and communicates them to the chromosome. The locations of its binding sites and the kinetics of its induction are consistent with a role for LR1 in regulation of isotype switching.
在用脂多糖（LPS）培养的原代小鼠B淋巴细胞的核提取物中，我们鉴定出一种可诱导的DNA结合活性，它是同种型转换重组的候选调节因子。这种LPS反应因子，我们称之为LR1，在用LPS培养的原代细胞中被诱导，其动力学与同种型转换重组平行。LR1结合来自Sγ1、Sγ3和Sα转换区以及重链增强子的序列，这些结合位点定义了一个在每个小鼠转换区都存在的共有序列。LR1活性存在于前B细胞和B细胞系中，但不存在于未用丝裂原培养的原代B细胞和高度分化的B细胞系中。LR1结合活性依赖于磷酸化，在用酸性磷酸酶孵育核提取物后会丧失。LR1活性的LPS诱导性和磷酸化依赖性表明，该因子监测细胞发育中依赖激酶的事件，并将其传递给染色体。其结合位点的位置和诱导动力学与LR1在同种型转换调节中的作用一致。
