Jurk M, Weissinger F, Lottspeich F, Schwarz U, Winnacker E L
Institut für Biochemie, Ludwig-Maximilians-Universität München, Germany.
Nucleic Acids Res. 1996 Jul 15;24(14):2799-806. doi: 10.1093/nar/24.14.2799.
SPSF I and II are two cellular proteins which bind specifically to single-stranded DNA. SPSF I and II binding sites are found in the minimal origin of replication of BPV-1 DNA and near the P2 promoter of the cellular c-myc gene. DNA-binding properties of the two proteins to single-stranded oligonucleotides of different lengths and sequences were quantified by determination of DNA-binding constants. The binding constant of SPSF proteins to the lower strand of the BPV-1 origin was determined to be 1.5 x 10(-10) M-1. Peptide sequences derived from purified SPSF I and II revealed the identity of at least one of the SPSF proteins with the so-called HeLa Pur alpha factor. The HeLa Pur alpha factor was identified previously by virtue of its capacity to bind to purine-rich strands of the PUR element found in initiation zones of DNA replication [Bergemann, A.D., Ma,Z.-W. and Johnson, E.M. (1992) Mol. Cell. Biol. 12, 5673-5682]. Expression of the Pur cDNA confirmed the identity of the Pur alpha protein with the 42 kDa SPSF I protein. Analysis of several Pur alpha cDNA clones revealed the existence of an extended 3'-untranslated region in all Pur mRNAs.
SPSF I和II是两种能特异性结合单链DNA的细胞蛋白。在BPV - 1 DNA的最小复制起点以及细胞c - myc基因的P2启动子附近发现了SPSF I和II的结合位点。通过测定DNA结合常数来量化这两种蛋白质与不同长度和序列的单链寡核苷酸的DNA结合特性。SPSF蛋白与BPV - 1起点下链的结合常数测定为1.5×10⁻¹⁰ M⁻¹。从纯化的SPSF I和II获得的肽序列显示，至少有一种SPSF蛋白与所谓的HeLa Purα因子相同。HeLa Purα因子先前是因其能够结合在DNA复制起始区发现的PUR元件的富含嘌呤链而被鉴定出来的[Bergemann, A.D., Ma, Z.-W.和Johnson, E.M. (1992) Mol. Cell. Biol. 12, 5673 - 5682]。Pur cDNA的表达证实了Purα蛋白与42 kDa的SPSF I蛋白相同。对几个Purα cDNA克隆的分析揭示了所有Pur mRNA中存在一个延伸的3'非翻译区。
