He Y, Chen H, Quon M J, Reitman M
Diabetes Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-1770, USA.
J Biol Chem. 1995 Dec 1;270(48):28887-91. doi: 10.1074/jbc.270.48.28887.
The obese gene product, leptin, regulates adiposity. Mice homozygous for a nonfunctional obese gene become massively obese and develop diabetes mellitus due to overeating and increased metabolic efficiency. The cDNA sequence of obese was recently reported (Zhang, Y., Proenca, R., Maffei, M., Barone, M., Leopold, L., and Friedman, J. L. (1994) Nature 372, 425-432; Correction: (1995 Nature 374, 479). We have determined the genomic organization of the 5' end of the mouse obese gene. The coding sequence is in exons 2 and 3. A single TATA-containing promoter was found upstream of exon 1. A minority (probably approximately 5%) of the obese mRNA contained an extra, untranslated exon between exons 1 and 2. Transcription of the obese gene was detected only in adipose cells. A 762-base pair obese gene promoter driving a luciferase gene yielded abundant activity in transiently transfected rat adipose cells in primary culture. The obese promoter was inactive in erythroid K562 cells. Deletion of bases from -762 downstream to -161 did not affect promoter activity in transfected adipose cells. The -161 minimal promoter contained consensus Sp1 and CCAAT/enhancer-binding protein (C/EBP) motifs. Cotransfection with C/EBP alpha (a transcription factor important in adipose cell differentiation) caused 23-fold activation. These data suggest that the obese promoter is a natural target of C/EBP alpha.
肥胖基因产物瘦素可调节肥胖状况。肥胖基因功能缺失的纯合子小鼠会因过度进食和代谢效率提高而变得极度肥胖并患上糖尿病。最近报道了肥胖基因的cDNA序列（张，Y.，普罗恩卡，R.，马费伊，M.，巴龙，M.，利奥波德，L.，和弗里德曼，J. L.（1994年）《自然》372卷，425 - 432页；勘误：（1995年《自然》374卷，479页））。我们已确定了小鼠肥胖基因5'端的基因组结构。编码序列存在于外显子2和3中。在第1外显子上游发现了一个单一的含TATA框的启动子。少数（可能约5%）的肥胖mRNA在第1和第2外显子之间含有一个额外的非翻译外显子。仅在脂肪细胞中检测到肥胖基因的转录。一个驱动荧光素酶基因的762碱基对的肥胖基因启动子在原代培养的瞬时转染大鼠脂肪细胞中产生了大量活性。肥胖基因启动子在红系K562细胞中无活性。从 - 762下游到 - 161缺失碱基并不影响转染脂肪细胞中的启动子活性。 - 161最小启动子含有共有Sp1和CCAAT/增强子结合蛋白（C/EBP）基序。与C/EBPα（在脂肪细胞分化中起重要作用的转录因子）共转染导致23倍的激活。这些数据表明肥胖基因启动子是C/EBPα的天然靶点。
