NyarkoAfuaBiochemBiophyNetworkAssemblyFactors.pdf
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Abstract
Eukaryotic ribosome biogenesis involves ~200 assembly
factors, but how these contribute to ribosome
maturation is poorly understood. Here, we
identify a network of factors on the nascent 60S subunit
that actively remodels preribosome structure. At its hub is
Rsa4, a direct substrate of the force-generating ATPase
Rea1. We show that Rsa4 is connected to the central
protuberance by binding to Rpl5 and to ribosomal RNA
(rRNA) helix 89 of the nascent peptidyl transferase center
(PTC) through Nsa2. Importantly, Nsa2 binds to helix 89
before relocation of helix 89 to the PTC. Structure-based
mutations of these factors reveal the functional importance
of their interactions for ribosome assembly. Thus,
Rsa4 is held tightly in the preribosome and can serve as
a “distribution box,” transmitting remodeling energy from
Rea1 into the developing ribosome. We suggest that a
relay-like factor network coupled to a mechano-enzyme is
strategically positioned to relocate rRNA elements during
ribosome maturation