(A) N-terminal sequences of PPL mutants with amino acid substitutions in bold and underlined, and deletions as dashes. FS(−1), FS(−2), FS(−3) contain deletions of one, two, three nucleotides, correspondingly, in the third codon. FS(−1, +1), FS(−2,+2) contain additional insertion of one or two nucleotides in the codon 29 to restore original reading frame. mRNAs were analyzed by Northern blots (B) or by qPCR (C; n=3, mean ± SD). (D) Deletions of natural signal sequences from PPL, AT, and CA4 lead to decrease in their mRNA levels (qPCR, n=3, mean ± SD). (E) Presence of a mutated signal sequence in hybrid cytosolic proteins leads to their mRNA depletion (qPCR, n=3, mean ± SD).