Specific ligation to double-stranded RNA for analysis of cellular RNA::RNA interactions

Double-stranded RNA (dsRNA) is formed in cells as intra- and intermolecular RNA interactions and is involved in a range of biological processes including RNA metabolism, RNA interference and translation control mediated by natural antisense RNA and microRNA. Despite this breadth of activities, few molecular tools are available to analyse dsRNA as native hybrids. We describe a two-step ligation method for enzymatic joining of dsRNA adaptors to any dsRNA molecule in its duplex form without a need for prior sequence or termini information. The method is specific for dsRNA and can ligate various adaptors to label, map or amplify dsRNA sequences. When combined with reverse transcription–polymerase chain reaction, the method is sensitive and can detect low nanomolar concentrations of dsRNA in total RNA. As examples, we mapped dsRNA/single-stranded RNA junctions within Escherichia coli hok mRNA and the human immunodeficiency virus TAR element using RNA from bacteria and mammalian cells

Rudiments of dual Feynman rules for Yang-Mills monopoles in loop space

Dual Feynman rules for Dirac monopoles in Yang-Mills fields are obtained by the Wu-Yang (1976) criterion in which dynamics result as a consequence of the constraint defining the monopole as a topological obstruction in the field. The usual path-integral approach is adopted, but using loop space variables of the type introduced by Polyakov (1980). An anti-symmetric tensor potential L_{\mu\nu}[\xi|s] appears as the Lagrange multiplier for the Wu-Yang constraint which has to be gauge-fixed because of the ``magnetic'' \widetilde{U}-symmetry of the theory. Two sets of ghosts are thus introduced, which subsequently integrate out and decouple. The generating functional is then calculated to order g^0 and expanded in a series in \widetilde{g}. It is shown to be expressible in terms of a local ``dual potential'' \widetilde{A}_\mu (x) found earlier, which has the same progagator and the same interaction vertex with the monopole field as those of the ordinary Yang-Mills potential A_\mu with a colour charge, indicating thus a certain degree of dual symmetry in the theory. For the abelian case the Feynman rules obtained here are the same as in QED to all orders in g, as expected by dual symmetry