The bacterial ribosomal protein S15 is located in the platform, a functional region of the 30S ribosomal subunit. While S15 is critical for in vitro formation of E. coli small subunits (SSUs), it is dispensable for in vivo biogenesis and growth. In this work, a novel synergistic interaction between rpsO, the gene that encodes S15, and rnc (the gene that encodes RNase III), was uncovered in E. coli. RNase III catalyzes processing of precursor ribosomal RNA (rRNA) transcripts and thus is involved in functional ribosome subunit maturation. Strains lacking S15 (ΔrpsO), RNase III (Δrnc) or both genes were examined to understand the relationship between these two factors and the impact of this double deletion on rRNA processing and SSU maturation. The double deletion of rpsO and rnc partially alleviates the observed cold sensitivity of ΔrpsO alone. A novel 16S rRNA precursor (17S∗ rRNA) that is detected in free 30S subunits of Δrnc is incorporated in 70S-like ribosomes in the double deletion. The stable accumulation of 17S∗ rRNA suggests that timing of processing events is closely coupled with SSU formation events in vivo. The double deletion has a suppressive effect on the cell elongation phenotype of ΔrpsO. The alteration of the phenotypes associated with S15 loss, due to the absence of RNase III, indicates that pre-rRNA processing and improvement of growth, relative to that observed for ΔrpsO, are connected. The characterization of the functional link between the two factors illustrates that there are redundancies and compensatory pathways for SSU maturation.

细菌核糖体蛋白 S15 位于平台，即 30S 核糖体亚基的功能区域。虽然 S15 对于大肠杆菌小亚基 (SSU)的体外形成至关重要，但它对于体内生物发生和生长是可有可无的。在这项工作中，在大肠杆菌中发现了rpsO （编码 S15 的基因）和rnc（编码 RNase III 的基因）之间的新型协同相互作用。RNase III 催化前体核糖体 RNA (rRNA) 转录物的加工，因此参与功能性核糖体亚基成熟。缺少 S15 ( ΔrpsO )、RNase III ( Δrnc) 或两个基因都进行了检查，以了解这两个因素之间的关系以及这种双缺失对 rRNA 加工和 SSU 成熟的影响。rpsO和rnc的双重缺失部分减轻了单独观察到的ΔrpsO的冷敏感性。在Δrnc的游离 30S 亚基中检测到的新型 16S rRNA 前体 (17S* rRNA)被掺入双缺失的 70S 样核糖体中。17S* rRNA 的稳定积累表明加工事件的时间与体内SSU 形成事件密切相关。双缺失对ΔrpsO 的细胞伸长表型具有抑制作用。由于不存在 RNase III，与 S15 丢失相关的表型的改变表明，相对于ΔrpsO观察到的，pre-rRNA 加工和生长的改善是相关的。这两个因素之间功能联系的表征表明，SSU 成熟存在冗余和补偿途径。