Flipping the switch to an active spliceosome

Article Abstract:

Spliceosomes catalyze the excision of introns from pre-messenger RNA. This highly ordered catalytic process is made possible by the assembly of a molecular machine that remains inactive until it is switched on by a sequential reorganization of the assembled components. Two studies on the mechanism of action underlying the activation process are reviewed. The first (Kuhn et al, 1999) focuses on the U1/U6 exchange reaction and its role in spliceosome activation while the second (Staley and Guthrie, 1999) focuses on the role of Prp28 on the ATP-mediated U1/U6 exchange.

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On base flipping

Article Abstract:

Base flipping developed during the evolution of DNA as the genetic material and now the phenomenon has been detected in cytosine-5 DNA methyltransferase M. Hhal, which flips the cytosine base out of the helix and into the active site. The phenomenon of base flipping is also evident in UDGase and Escherichia coli photolyase but the enzyme-DNA interactions have not been crystalized. The evidence for base flipping in various enzymes is discussed.

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Flipping riboswitches

Article Abstract:

Five high-resolution crystal structures have provided a comprehensive view of how riboswitches sense their ligands and points to new challenges in this emerging field. These new structures have helped in designing more specific and safer riboswitch-targeting drugs.

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