Bergemann A D, Ma Z W, Johnson E M
Department of Pathology, Mount Sinai Medical School, New York, New York 10029.
Mol Cell Biol. 1992 Dec;12(12):5673-82. doi: 10.1128/mcb.12.12.5673-5682.1992.
The human Pur factor binds strongly to a sequence element repeated within zones of initiation of DNA replication in several eukaryotic cells. The protein binds preferentially to the purine-rich single strand of this element, PUR. We report here the cloning and sequencing of a cDNA encoding a protein with strong affinity for the PUR element. Analysis with a series of mutated oligonucleotides defines a minimal single-stranded DNA Pur-binding element. The expressed Pur open reading frame encodes a protein of 322 amino acids. This protein, Pur alpha, contains three repeats of a consensus motif of 23 amino acids and two repeats of a second consensus motif of 26 amino acids. Near its carboxy terminus, the protein possesses an amphipathic alpha-helix and a glutamine-rich domain. The repeat region of Pur cDNA is homologous to multiple mRNA species in each of several human cell lines and tissues. The HeLa cDNA library also includes a clone encoding a related gene, Pur beta, containing a version of the 23-amino-acid consensus motif similar, but not identical, to those in Pur alpha. Results indicate a novel type of modular protein with capacity to bind repeated elements in single-stranded DNA.
人类Pur因子能与几种真核细胞中DNA复制起始区域内重复的序列元件紧密结合。该蛋白优先结合此元件富含嘌呤的单链，即PUR。我们在此报告编码与PUR元件具有强亲和力的蛋白质的cDNA的克隆和测序。用一系列突变的寡核苷酸进行分析确定了最小的单链DNA Pur结合元件。表达的Pur开放阅读框编码一个含322个氨基酸的蛋白质。这种蛋白质，即Purα，包含三个23个氨基酸的共有基序重复序列和两个26个氨基酸的第二个共有基序重复序列。在其羧基末端附近，该蛋白质具有一个两亲性α螺旋和一个富含谷氨酰胺的结构域。Pur cDNA的重复区域与几种人类细胞系和组织中的多种mRNA种类同源。HeLa cDNA文库还包含一个编码相关基因Purβ的克隆，该基因含有一个与Purα中相似但不完全相同的23个氨基酸共有基序版本。结果表明这是一种新型的模块化蛋白质，具有结合单链DNA中重复元件的能力。
