HEK293T cells were pulse labelled with [35S]methionine in the presence of puromycin (2 µg/ml). During puromycin treatment, cells were incubated for 5 min and 10 min in medium lacking [35S]methionine. Anti-FLAG immunoisolations were performed as described and eluates analyzed as described in Fig. 4C. Total 1 %, Eluates 100 %. The signal of ND2 was graphed after normalization against the COX2 signal and the signal of mature ND2 in the 5 min chase sample was set as 100 % (error bars indicate SEM from three biological replicates; *p < 0,05; paired t-test). Red asterisks, accumulating nascent chains of ND2. 