Zhou Mo, Kuruvilla Leena, Shi Xiarong, Viviano Stephen, Ahearn Ian M, Amendola Caroline R, Su Wenjuan, Badri Sana, Mahaffey James, Fehrenbacher Nicole, Skok Jane, Schlessinger Joseph, Turk Benjamin E, Calderwood David A, Philips Mark R
Perlmutter Cancer Center, NYU Langone Health, New York, NY 10016.
Department of Pharmacology, Yale School of Medicine, New Haven, CT 06510.
Proc Natl Acad Sci U S A. 2020 Dec 15;117(50):31914-31922. doi: 10.1073/pnas.2005712117. Epub 2020 Nov 30.
Inhibiting membrane association of RAS has long been considered a rational approach to anticancer therapy, which led to the development of farnesyltransferase inhibitors (FTIs). However, FTIs proved ineffective against -driven tumors. To reveal alternative therapeutic strategies, we carried out a genome-wide CRISPR-Cas9 screen designed to identify genes required for KRAS4B membrane association. We identified five enzymes in the prenylation pathway and SAFB, a nuclear protein with both DNA and RNA binding domains. Silencing led to marked mislocalization of all RAS isoforms as well as RAP1A but not RAB7A, a pattern that phenocopied silencing , the prenyltransferase α subunit shared by farnesyltransferase and geranylgeranyltransferase type I. We found that SAFB promoted RAS membrane association by controlling FNTA expression. knockdown decreased GTP loading of RAS, abrogated alternative prenylation, and sensitized -mutant cells to growth inhibition by FTI. Our work establishes the prenylation pathway as paramount in KRAS membrane association, reveals a regulator of prenyltransferase expression, and suggests that reduction in FNTA expression may enhance the efficacy of FTIs.
长期以来，抑制RAS与膜的结合一直被认为是一种合理的抗癌治疗方法，这促使了法尼基转移酶抑制剂（FTIs）的研发。然而，FTIs被证明对KRAS驱动的肿瘤无效。为了揭示其他治疗策略，我们进行了一项全基因组CRISPR-Cas9筛选，旨在鉴定KRAS4B与膜结合所需的基因。我们在异戊二烯化途径中鉴定出五种酶以及SAFB，一种具有DNA和RNA结合结构域的核蛋白。沉默SAFB导致所有RAS亚型以及RAP1A明显的定位错误，但不影响RAB7A，这种模式与沉默FNTα相似，FNTα是法尼基转移酶和I型香叶基香叶基转移酶共有的异戊二烯转移酶α亚基。我们发现SAFB通过控制FNTA的表达促进RAS与膜的结合。敲低SAFB会降低RAS的GTP负载，消除替代异戊二烯化，并使KRAS突变细胞对FTIs介导的生长抑制敏感。我们的工作确立了异戊二烯化途径在KRAS与膜结合中的首要地位，揭示了异戊二烯转移酶表达的调节因子，并表明降低FNTA的表达可能会增强FTIs的疗效。
