Collins M, Smith A A, Parker M I
Department of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Observatory, South Africa.
J Cell Biochem. 1998 Sep 15;70(4):455-67.
Both the mouse and human alpha2(I) procollagen promoters contain an inverted CCAAT box at -80, but only the human promoter contains an additional regulatory element, the collagen modulating element (CME), immediately downstream of the CCAAT box [Collins et al. (1997): Biochem J 322:199-206]. In this study, the transcription factors that bind to the G/CBE and CME within the human promoter were characterized in SVWI-38 and CT-1 nuclear extracts. Two distinct proteins bind to the CME, and both were identified as heat-labile factors that were sensitive to high ionic strengths and required Zn2+ for DNA-binding activity. These proteins had Stokes radii of 4.12 and 3.15 nm, sedimentation coefficients of 3.9 and 3.2 S and native molecular weights of 66 and 41 kDa, respectively. On the basis of biochemical and DNA-binding properties, the CME binding proteins are probably novel factors involved in the regulation of the human alpha2(I) procollagen gene. By contrast, the G/CBE binding proteins were more resistant to heat, ionic strength, and divalent metal ion chelators, demonstrating that the G/CBE and CME binding proteins had distinct DNA-binding properties. The above properties suggest that this factor is a member of the previously characterized family of CCAAT box-binding factors, CBF, NF-Y, CP-1 and alpha-CP1. Taken together, these physicochemical properties of the COL1A2 CCAAT box and CME-binding proteins demonstrated that they were distinct unrelated transcription factors. These results also suggest that there is a distinct difference in the DNA-binding activity between the equivalent region of the mouse and human alpha2(I) procollagen promoters.
小鼠和人类α2（I）前胶原启动子在-80处均含有一个反向CCAAT框，但只有人类启动子在CCAAT框的紧邻下游含有一个额外的调控元件，即胶原调节元件（CME）[柯林斯等人（1997年）：《生物化学杂志》322卷：199 - 206页]。在本研究中，在SVWI - 38和CT - 1核提取物中对结合于人启动子内G/CBE和CME的转录因子进行了表征。有两种不同的蛋白质结合到CME上，且二者均被鉴定为对热不稳定的因子，它们对高离子强度敏感，并且DNA结合活性需要Zn2+。这些蛋白质的斯托克斯半径分别为4.12和3.15纳米，沉降系数分别为3.9和3.2 S，天然分子量分别为66和41 kDa。基于生化和DNA结合特性，CME结合蛋白可能是参与人类α2（I）前胶原基因调控的新因子。相比之下，G/CBE结合蛋白对热、离子强度和二价金属离子螯合剂更具抗性，这表明G/CBE和CME结合蛋白具有不同的DNA结合特性。上述特性表明该因子是先前已表征的CCAAT框结合因子家族（CBF、NF - Y、CP - 1和α - CP1）的成员。综上所述，COL1A2 CCAAT框和CME结合蛋白的这些物理化学特性表明它们是不同的不相关转录因子。这些结果还表明，小鼠和人类α2（I）前胶原启动子的等效区域之间的DNA结合活性存在明显差异。
