Volker J L, Rameh L E, Zhu Q, DeCaprio J, Hansen U
Dana-Farber Cancer Institute, and Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Genes Dev. 1997 Jun 1;11(11):1435-46. doi: 10.1101/gad.11.11.1435.
The mammalian transcription factor LSF (CP2/LBP-1c) binds cellular promoters modulated by cell growth signals. We demonstrate here that LSF-DNA-binding activity is strikingly regulated by induction of cell growth in human peripheral T lymphocytes. Within 15 min of mitogenic stimulation of these cells, the level of LSF-DNA-binding activity increased by a factor of five. The level of LSF protein in the nucleus remained constant throughout this interval. However, a rapid decrease in the electrophoretic mobility of LSF, attributable to phosphorylation, correlated with the increase in DNA-binding activity. pp44 (ERK1) phosphorylated LSF in vitro on the same residue that was phosphorylated in vivo, specifically at amino acid position 291, as indicated by mutant analysis. As direct verification of the causal relationship between phosphorylation and DNA-binding activity, treatment in vitro of LSF with phosphatase both increased the electrophoretic mobility of the protein and decreased LSF-DNA-binding activity. This modulation of LSF-DNA-binding activity as T cells progress from a resting to a replicating state reveals that LSF activity is regulated during cell growth and suggests that LSF regulates growth-responsive promoters.
哺乳动物转录因子LSF（CP2/LBP-1c）可结合受细胞生长信号调控的细胞启动子。我们在此证明，在人外周血T淋巴细胞中，细胞生长的诱导对LSF与DNA的结合活性有显著调控作用。在这些细胞受到促有丝分裂刺激后的15分钟内，LSF与DNA的结合活性水平增加了五倍。在此期间，细胞核中LSF蛋白的水平保持恒定。然而，由于磷酸化作用导致LSF电泳迁移率迅速下降，这与DNA结合活性的增加相关。如通过突变分析所示，pp44（ERK1）在体外将LSF磷酸化的位点与体内磷酸化位点相同，具体为氨基酸位置291。作为磷酸化与DNA结合活性之间因果关系的直接验证，用磷酸酶在体外处理LSF，既增加了蛋白质的电泳迁移率，又降低了LSF与DNA的结合活性。随着T细胞从静止状态进入复制状态，LSF与DNA结合活性的这种调节表明，LSF活性在细胞生长过程中受到调控，并且提示LSF可调节生长反应性启动子。
