Journal: Nature Communications
Article Title: Usb1 controls U6 snRNP assembly through evolutionarily divergent cyclic phosphodiesterase activities
Figure Lengend Snippet: yUsb1 acts as a 3′–5′exonuclease and CPDase in vitro. a U6 snRNA is synthesized by RNA Polymerase III. Transcription termination produces a heterogeneous U6 with a 4–8 nucleotide U-tail. Processing by yUsb1 shortens the U-tail and leaves a phosphoryl group. b Usb1 removes nucleotides from the 3′ end of RNAs. The 5′-labeled U6 95–112+3U oligonucleotide cis -diol substrate (lane 2) is insensitive to CIP (lane 3) or T4 PNK (lane 4) treatment. Incubation with yUsb1 for 1 h results in a shorter product (lane 5). Similar reactivity of the product to both CIP (lane 6) and T4 PNK (lane 7) indicates that the product is a noncyclic phosphate. An alkaline hydrolysis ladder (lane 1) shows the mobility of oligonucleotide products of different lengths. ( c , top ) One-dimensional 31 P NMR spectra of 2′,3′-cUMP shows a single peak at 20 ppm. A 3′ UMP standard has a single peak at 3.4 ppm. When 2′,3′-cUMP is incubated with AtRNL, which leaves a 2′ phosphate 8 , there is a single peak at 3.2 ppm. Incubation of 2′,3′-cUMP with yUsb1 produces a new signal at 3.4 ppm ( c , bottom ) Zoom of dashed region in top panel. d Time course of Usb1 processing on RNAs with different 3′ end modifications. yUsb1 is most active on RNA substrates with a cis -diol (lanes 1–4), less active on those with a 2′,3′-cyclic phosphate ( > p; lanes 5–8) or 2′ phosphates (2′P; lanes 9–12), and is inactive on 3′ phosphate ends (3′P; lanes 13–16). e Model describing the dual activities of yUsb1
Article Snippet: Samples were treated with CIP or T4 PNK by addition of “Cutsmart” or “PNK” buffer from New England Biolabs and 10 units of CIP or T4 PNK and incubation at 37 °C for 15 min. Mock treated samples contained only Cutsmart buffer and water in lieu of CIP or T4 PNK.
Techniques: In Vitro, Synthesized, Labeling, Incubation, Nuclear Magnetic Resonance