The P9.1-P9.2 peripheral extension helps guide folding of the Tetrahymena ribozyme.

We have previously proposed a hierarchical model for the folding mechanism of the Tetrahymena ribozyme that may illustrate general features of the folding pathways of large RNAs. While the role of elements in the conserved catalytic core of this ribozyme during the folding process is beginning to emerge, the participation of non-conserved peripheral extensions in the kinetic folding mechanism has not yet been addressed. We now show that the 3'-terminal P9.1-P9.2 extension of the Tetrahymena ribozyme plays an important role during the folding process and appears to guide formation of the catalytic core.