Interaction between Pur α and ssCRE, and Pur α binding proteins

Purα是脑中丰富的蛋白质，与（GGN）n序列（PUR元件）结合。在PUR元件（ssCRE：单链cAMP反应元件）存在或不存在CaM的情况下，GST Pur α的免疫反应性增强或银染均反映了Purα的DNA结合活性。用小鼠脑内源性Purα也观察到类似的结果。结果表明，Purα结合蛋白的检测结果与凝胶迁移法相当，免疫印迹法的灵敏度与凝胶迁移法相当，并尝试以GST Pur α为配体，用重叠法寻找Purα结合蛋白。三种PurBP主要存在于核提取物（N.Ext.）用N. Ext.胰蛋白酶，但不与RNA酶或DNA酶。加入含有PUR元件的ssCRE后，三个PurBP消失，但ΔGGN ssCRE不会消失。PurBPs在脑内以Purα形式大量表达。

Purα is an abundant protein in the brain and binds to a (GGN)n sequence, PUR element. The increased-immunoreactivity or silver staining of GST-Pur α in the presence of PUR element (ssCRE: single stranded cAMP response element) with or without CaM reflects well the DNA-binding activity of Purα. The similar results were observed with endogenous Purα from mouse brain. These data were just comparable to those of the gel shift assay and sensitivity with the immunoblot was comparable with that of the gel shift assay.We also tried to search for Purα binding proteins (PurBPs) by the overlay assay with GSTPurα as a ligand. Three PurBPs were found mostly in the nuclear extract (N.Ext.) and they w6re not detected by the pretreatment of N.Ext. with trypsin, but not with RNase or DNase. The three PurBPs disappeared by the addition of ssCRE containing a PUR element, but not by ΔGGN ssCRE). The PurBPs were abundantly expressed in the brain as Purα.