Running Rings Around RNA: The role of Ro RNPs in RNA maturation and decay

Abstract

The Ro 60 kDa protein is a ring‐shaped RNA binding protein that is present in many animal cells and certain prokaryotes. In both animal cells and bacteria, Ro is found complexed with ~100 nt small RNAs called Y RNAs. In vertebrate cells, Ro also binds misfolded RNAs and likely functions in noncoding RNA quality control. Structural and biochemical studies have revealed that Y RNAs bind on the outer surface of the Ro ring. In contrast, the single‐stranded ends of misfolded RNAs insert into the central cavity, while helical portions of these RNAs bind to a large basic platform on the outer surface. Because the binding of Ro to misfolded RNA is largely sequence‐nonspecific, Ro may be able to associate with a variety of structured RNAs that contain both a single‐stranded 3′ end and helices. Consistent with this hypothesis, Ro is required for efficient maturation of 23S rRNA in the eubacterium D. radiodurans. The binding of Y RNAs and other RNAs is mutually exclusive, and studies in bacteria have revealed that one role of Y RNAs is to regulate access of other RNAs to Ro. We are examining the various functions of Ro and the Y RNAs in both mammalian cells and bacteria.