Assembly Factors and snoRNAs Manage Programmable RNA Folding and Misfolding to Support Growth in Stationary Phase

We show that assembly factors Rrp36 and snoRNAs (snR31, snR54) cooperatively prevent this misfolding by tethering Rrp5 away from the platform and delaying h24 formation, respectively. Disrupting these interactions leads to widespread structural alterations that persist into mature ribosomes.

Interestingly, we reveal that this misfolding pathway is not an evolutionary mistake but rather serves a physiological function. This work reframes assembly factors and snoRNAs as molecular chaperones that actively reshape the RNA folding landscape, with broader implications for understanding ribosome heterogeneity and conditional ribosome specialization.