SsrA-mediated trans-translation plays a role in mRNA quality control by facilitating degradation of truncated mRNAs

Northern blot analysis of mRNAs derived from naturally terminatorless genes. TA331 (ssrA⁻), W3110 (ssrA⁺), and TA371 (ssrA^DD), harboring pMelR or pSoxR, were grown to OD₆₀₀ = 0.7. The synthesis of mRNAs was induced for 20 min by adding 0.1 mM IPTG. Total RNAs (5 μg) were subjected to Northern blot analysis using a DIG-labeled probe specific to the 5′ portion of melR or soxR mRNA. Asterisks indicate the extended mRNAs that reached the λ t0 terminator derived from the vector. The vertical bars represent the truncated mRNAs. The sizes of the melR- and soxR-mRNA coding regions are ∼1050 and ∼550 nt, respectively. The positions of RNA size markers are shown on the right.