In addition, we used mutational analysis to determine learn more the relative role of the EBS-IBS 1 and 2 recognition elements during

splicing by these introns. We show that group IIE and IIF introns are indeed distinct active intron families, with different reactivities and structures. We show that the group IIE introns self-splice exclusively through the hydrolytic pathway, while group IIF introns can also catalyze transesterifications. Intriguingly, we observe one group IIF intron that forms circular intron. Finally, despite an apparent EBS2-IBS2 duplex in the sequences of these introns, we find that this interaction plays no role during self-splicing in vitro. It is now clear that the group IIE and IIF introns are functional ribozymes, with distinctive properties that may be useful for biotechnological applications, and which may contribute to the biology of host organisms.”
“Pseudouridines (Psi) are found in structurally and functionally important regions of RNAs. Six families of Psi synthases, TruA,

TruB, TruD, RsuA, RluA, and Pus10 have been identified. Pus10 is present in Archaea and Eukarya. While most archaeal Pus10 produce both tRNA Psi 54 and Psi 55, some produce only Psi 55. Interestingly, human PUS10 has been implicated in apoptosis and Crohn’s and Celiac diseases. Homology models of archaeal Pus10 proteins based on the crystal structure of human PUS10 reveal that there are subtle

structural MG-132 cost O-methylated flavonoid differences in all of these Pus10 proteins. These observations suggest that structural changes in homologous proteins may lead to loss, gain, or change of their functions, warranting the need to study the structure-function relationship of these proteins. Using comparison of structural models and a series of mutations, we identified forefinger loop ( reminiscent of that of RluA) and an Arg and a Tyr residue of archaeal Pus10 as critical determinants for its Psi 54, but not for its Psi 55 activity. We also found that a Leu residue, in addition to the catalytic Asp, is essential for both activities. Since forefinger loop is needed for both rRNA and tRNA Psi synthase activities of RluA, but only for tRNA Psi 54 activity of Pus10, archaeal Pus10 proteins must use a different mechanism of recognition for Psi 55 activity. We propose that archaeal Pus10 uses two distinct mechanisms for substrate uridine recognition and binding. However, since we did not observe any mutation that affected only Psi 55 activity, both mechanisms for archaeal Pus10 activities must share some common features.”
“The molecular evolutionary signatures of miRNAs inform our understanding of their emergence, biogenesis, and function. The known signatures of miRNA evolution have derived mostly from the analysis of deeply conserved, canonical loci.