Hasegawa S L, Doetsch P W, Hamilton K K, Martin A M, Okenquist S A, Lenz J, Boss J M
Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322.
Nucleic Acids Res. 1991 Sep 25;19(18):4915-20. doi: 10.1093/nar/19.18.4915.
A number of eukaryotic DNA binding proteins have been isolated by screening phage expression libraries with DNA probes containing the binding site of the DNA-binding protein. This methodology was employed here to isolate clones of the factor that interacts with the W box element of the human major histocompatibility complex HLA-DQB gene. Surprisingly, several cDNA clones of YB-1, a cDNA clone that was previously isolated with a CCAAT element-containing sequence were found. Independently, the screening of phage expression libraries with depurinated DNA resulted in the isolation of YB-1 and dbpA, a previously isolated cDNA that has homology to YB-1. Additional characterization of YB-1 showed that it bound a wide variety of DNA sequences and suggested that the binding of this protein is promiscuous. Furthermore, we show that both YB-1 and dbpA bind to depurinated DNA better than undamaged DNA and that the extent of specificity of binding is influenced by Mg2+. Due to the lack of sequence specificity and high degree of binding to depurinated DNA, we suggest that these proteins might be involved in chromosome functions such as maintenance of chromatin structure or DNA repair that do not require sequence-specific binding.
通过用含有DNA结合蛋白结合位点的DNA探针筛选噬菌体表达文库，已分离出许多真核生物DNA结合蛋白。本文采用该方法分离与人类主要组织相容性复合体HLA - DQB基因的W盒元件相互作用的因子的克隆。令人惊讶的是，发现了几个YB - 1的cDNA克隆，YB - 1是先前用含CCAAT元件的序列分离出的一个cDNA克隆。独立地，用脱嘌呤DNA筛选噬菌体表达文库导致分离出YB - 1和dbpA，dbpA是先前分离出的与YB - 1具有同源性的cDNA。对YB - 1的进一步表征表明它能结合多种DNA序列，这表明该蛋白的结合是杂乱的。此外，我们表明YB - 1和dbpA与脱嘌呤DNA的结合都比与未受损DNA的结合更好，并且结合特异性的程度受Mg2 +的影响。由于缺乏序列特异性以及与脱嘌呤DNA的高度结合，我们认为这些蛋白可能参与染色体功能，如维持染色质结构或DNA修复，而这些功能不需要序列特异性结合。
