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. Author manuscript; available in PMC: 2015 Jan 16.
Published in final edited form as: Cell. 2014 Jan 16;156(0):146–157. doi: 10.1016/j.cell.2013.12.017

Figure 4. Functional Signal Sequence is Required for Protection of the Secretory Protein mRNA from Degradation.

Figure 4

(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).