Choi J Y, Stukey J, Hwang S Y, Martin C E
Nelson Biological Laboratory, Bureau of Biological Research, Department of Biological Sciences, Rutgers University, Busch Campus, Piscataway, New Jersey 08855-1059, USA.
J Biol Chem. 1996 Feb 16;271(7):3581-9. doi: 10.1074/jbc.271.7.3581.
In Saccharomyces cerevisiae, unsaturated fatty acids are formed from saturated acyl-CoA precursors by Ole1p, a delta-9 fatty acid desaturase. OLE1 mRNA levels are differentially regulated by the addition of saturated or unsaturated fatty acids to the growth medium. One component of this regulation system involves the control of OLE1 transcription. Saturated fatty acids induce a 1.6-fold increase in transcription activity, whereas a large family of unsaturated fatty acids repress OLE1 transcription as much as 60-fold. A deletion analysis of OLE1 promoter::lacZ fusion reporter genes identified a 111-base pair (bp) fatty acid-regulated (FAR) region approximately 580 bp upstream of the start codon that is essential for transcription activation and unsaturated fatty acid repression. Deletion of an 88-bp sequence within that region resulted in a complete loss in transcription activation and unsaturated fatty acid regulation. The 111-bp FAR element strongly activates transcription and confers unsaturated fatty acid regulation on a heterologous CYC1 promoter test plasmid. Essential elements required for unsaturated fatty acid repression of OLE1 were found in the 5 and 3 region of the 111-bp sequence. The FAR element-mediated activation and fatty acid repression of transcription was found to be closely tied to fatty acyl-CoA metabolism. Two fatty acid activation genes, FAA1 and FAA4, were found to be essential for unsaturated fatty acid repression of OLE1 through the FAR sequences. Disruption of either gene results in reduced levels of unsaturated fatty acid repression; disruption of both genes completely blocks the regulatory response. Acyl-CoA binding protein (ACBP) plays a role in determining the level of FAR element activated transcription. Disruption of the ACBP gene causes a >5-fold activation of OLE1 transcription and a similar increase in OLE1 mRNA levels. Unsaturated fatty acid repression of OLE1 transcription, however, is not affected by the disrupted ACBP gene. These studies show that promoter elements responsible for unsaturated fatty acid-mediated transcription repression are tightly linked to OLE1 activation sequences and that OLE1 transcription levels are closely tied to acyl-CoA metabolism.
在酿酒酵母中，不饱和脂肪酸由δ-9脂肪酸去饱和酶Ole1p从饱和酰基辅酶A前体合成。通过向生长培养基中添加饱和或不饱和脂肪酸，可对OLE1 mRNA水平进行差异调节。该调节系统的一个组成部分涉及对OLE1转录的控制。饱和脂肪酸可使转录活性增加1.6倍，而一大类不饱和脂肪酸可将OLE1转录抑制多达60倍。对OLE1启动子::lacZ融合报告基因进行缺失分析，确定了起始密码子上游约580 bp处一个111碱基对（bp）的脂肪酸调节（FAR）区域，该区域对于转录激活和不饱和脂肪酸抑制至关重要。删除该区域内一个88 bp的序列会导致转录激活和不饱和脂肪酸调节完全丧失。111 bp的FAR元件强烈激活转录，并赋予异源CYC1启动子测试质粒不饱和脂肪酸调节能力。在111 bp序列的5′和3′区域发现了OLE1不饱和脂肪酸抑制所需的必需元件。发现FAR元件介导的转录激活和脂肪酸抑制与脂肪酰基辅酶A代谢密切相关。发现两个脂肪酸激活基因FAA1和FAA4对于通过FAR序列对OLE1进行不饱和脂肪酸抑制至关重要。任一基因的破坏都会导致不饱和脂肪酸抑制水平降低；两个基因都破坏则完全阻断调节反应。酰基辅酶A结合蛋白（ACBP）在确定FAR元件激活转录的水平中起作用。ACBP基因的破坏导致OLE1转录激活>5倍，且OLE1 mRNA水平有类似增加。然而，OLE1转录的不饱和脂肪酸抑制不受ACBP基因破坏的影响。这些研究表明，负责不饱和脂肪酸介导的转录抑制的启动子元件与OLE1激活序列紧密相连，且OLE1转录水平与酰基辅酶A代谢密切相关。
