Přehled o publikaci

Bacterial ribosome assembly is a highly coordinated, multistep process essential for cellular viability. It begins with the transcription, folding, and extensive modification of ribosomal RNA (rRNA), followed by the hierarchical incorporation of ribosomal proteins into pre-ribosomal particles. This process is guided by a network of specialised assembly factors, including RNA chaperones, GTPases, rRNA modification enzymes, and quality control proteins, which ensure accurate folding, prevent kinetic traps, and license subunits for translation. Disruption of these factors can stall assembly at specific checkpoints, leading to the accumulation of immature particles, reduced translational capacity, and growth defects. In Escherichia coli , the small ribosomal subunit assembly factor RimM plays a central role in the late stages of 30S maturation, facilitating the correct positioning of key ribosomal proteins in the head domain. Deletion of rimM results in slow growth, accumulation of assembly assembly-arrested 30S particles, and impaired translation efficiency. Intriguingly, despite these defects, bacterial growth can gradually recover over time, indicating that compensatory mechanisms can remodel the translation apparatus to bypass the block in canonical assembly. Such adaptation reflects the inherent plasticity of ribosome biogenesis and suggests the existence of alternative maturation pathways that integrate with global translation control. Here, we show that this adaptation involves coordinated actions of the ribosomal silencing factor RsfS 5 and translation initiation factors. Using high-resolution cryo-electron microscopy, we demonstrate that initiation factors associate with immature 30S subunits, preventing premature subunit joining until 30S assembly is complete. In parallel, RsfS binds to 50S subunits, blocking their association with incompletely matured 30S subunits. Together, these mechanisms safeguard translation fidelity during late stages of ribosome biogenesis. Our results reveal a previously unrecognised layer of quality control in bacterial ribosome maturation, in which ribosome-associated factors act cooperatively to maintain translation under biogenesis stress.