(A) mRNA levels of CHOP, Cox7a2l/SCAF1 or Cox7a2 measured by qPCR in U2OS cells cultured under galactose at the indicated time points. (B) Galactose-induced mRNA expression levels of SCAF1 in cells cultured in the presence of PERK or eIF2α phosphorylation (ISRIB) inhibitors. (C) SCAF1 mRNA levels upon PERK activation with DHBDC or CCT020312. (D) SC levels, (E) mitochondrial respiration, (F) ATP/ADP ratios and (G) cell proliferation in galactose in CRISPR-Cas9 SCAF1 ablated cells. (H) SC levels, (I) mitochondrial respiration, (J) ATP/ADP ratios, and (K) cell proliferation of ATF4 ablated cells cultured in galactose media. (L) SC levels (left) and cell proliferation (right) under galactose, in ATF4 or PERK depleted cells (for 4 days) with or without ectopic overexpression of SCAF1. Immunoblots shown are representative of >3 independent experiments using CII (anti-SDHA) as a loading control. All other experiments are the mean ± s.e.m., n>3. Asterisks denote *p<0.05, **p<0.01 or ***p<0.001. For two comparisons a two-tailed t-test was used, for multiple comparisons, one-way ANOVA with Bonferroni post-test was applied. gluc, glucose. Galac, galactose. CCT, CCT020312.