U2 snRNA is inducibly pseudouridylated at novel sites by Pus7p and snR81 RNP

All pseudouridines identified in RNA are considered constitutive modifications. Here, we demonstrate that pseudouridylation of Saccharomyces cerevisiae U2 snRNA can be conditionally induced. While only Psi 35, Psi 42 and Psi 44 are detected in 112 under normal conditions, nutrient deprivation leads to additional pseudouridylation at positions 56 and 93. Pseudouridylation at position 56 can also be induced by heat shock. Detailed analyses have shown that Pus7p, a single polypeptide pseudouridylase known to modify 112 at position 35 and tRNA at position 13, catalyses Psi 56 formation, and that snR81 RNP, a box H/ACA RNP known to modify 112 snRNA at position 42 and 25S rRNA at position 1051, catalyses Psi 93 formation. Using mutagenesis, we have demonstrated that the inducibility can be attributed to the imperfect substrate sequences. By introducing Psi 93 into log-phase cells, we further show that Psi 93 has a role in pre-mRNA splicing. Our results thus demonstrate for the first time that pseudouridylation of RNA can be induced at sites of imperfect sequences, and that Pus7p and snR81 RNP can catalyse both constitutive and inducible pseudouridylation. The EMBO Journal (2011) 30, 79-89. doi:10.1038/ emboj.2010.316; Published online 3 December 2010 Subject Categories: RNA