The de novo synthesis of fatty acids has emerged as a therapeutic target for various diseases, including cancer. Because cancer cells are intrinsically buffered to combat metabolic stress, it is important to understand how cells may adapt to the loss of de novo fatty acid biosynthesis. Here, we use pooled genome-wide CRISPR screens to systematically map genetic interactions (GIs) in human HAP1 cells carrying a loss-of-function mutation in fatty acid synthase (FASN), whose product catalyses the formation of long-chain fatty acids. FASN-mutant cells show a strong dependence on lipid uptake that is reflected in negative GIs with genes involved in the LDL receptor pathway, vesicle trafficking and protein glycosylation. Further support for these functional relationships is derived from additional GI screens in query cell lines deficient in other genes involved in lipid metabolism, including LDLR, SREBF1, SREBF2 and ACACA. Our GI profiles also identify a potential role for the previously uncharacterized gene C12orf49 (which we call LUR1) in regulation of exogenous lipid uptake through modulation of SREBF2 signalling in response to lipid starvation. Overall, our data highlight the genetic determinants underlying the cellular adaptation associated with loss of de novo fatty acid synthesis and demonstrate the power of systematic GI mapping for uncovering metabolic buffering mechanisms in human cells.

脂肪酸的从头合成已经成为包括癌症在内的各种疾病的治疗靶标。因为癌细胞固有地被缓冲以抵抗代谢压力，所以了解细胞如何适应从头脂肪酸生物合成的损失很重要。在这里，我们使用汇集的全基因组CRISPR筛选系统地对人类HAP1细胞中的遗传相互作用（GI）进行系统定位，这些人类HAP1细胞携带脂肪酸合酶（FASN）的功能丧失突变，其产物催化长链脂肪酸的形成。财务会计准则突变细胞显示出对脂质摄取的强烈依赖性，这反映在具有与LDL受体途径，囊泡运输和蛋白质糖基化有关的基因的阴性GI中。对这些功能关系的进一步支持来自查询细胞系中缺乏其他参与脂质代谢的基因（包括LDLR，SREBF1，SREBF2和ACACA）的GI筛选。我们的GI资料还确定了以前未鉴定的基因C12orf49（我们称为LUR1）的潜在作用）通过调节SREBF2信号转导来响应脂质饥饿，从而调节外源性脂质的摄取。总体而言，我们的数据突出显示了与从头脂肪酸合成损失相关的细胞适应性的遗传决定因素，并证明了系统的GI映射功能可揭示人细胞中的代谢缓冲机制。