Lipardi C et al. (2009) Proc Natl Acad Sci U S A "Identification of an RNA-dependent RNA polymerase in Drosophila involved in RNAi and transposon suppression."

Lipardi C, Paterson BM

[Proc Natl Acad Sci U S A, 2009]

Here, we show that recombinant Drosophila elp1 (D-elp1) produced in Sf9 cells or Escherichia coli, corresponding to the largest of the three subunits in the RNA polymerase II core elongator complex, has RNA-dependent RNA polymerase (RdRP) activity. D-elp1 is a noncanonical RdRP that can synthesize dsRNA from different ssRNA templates using either a primer-dependent or primer-independent initiation mechanism. Of the three core subunits, only D-elp1 depletion inhibits RNAi in S2 cells but does not affect micro RNA function. Furthermore, D-elp1 depletion results in increased steady state levels of representative transposon RNAs and a decrease in the corresponding transposon antisense transcripts and endo siRNAs. In contrast, although Dcr-2 depletion results in increased transposon RNA levels and a reduction in the corresponding endo siRNAs, there is no change in the transposon antisense RNA levels. In D-elp1 null third instar larvae transposon RNA levels are also increased and the corresponding transposon antisense RNAs are reduced. D-elp1 associates tightly with Dcr-2, similar to the Dicer-RdRP interaction observed in lower eukaryotes. These results identify an aspect of the RNAi pathway in Drosophila that suggest transposon derived endo siRNAs, critical for transposon suppression, are produced, in part, in a D-elp1 dependent step that converts transposon RNA into dsRNA that is subsequently processed by Dcr-2. The generality of this mechanism in genome defense and RNA silencing in higher eukaryotes is suggested.

Clovis Y et al. (2016) MicroPubl Biol "Mutations in KCNQ potassium channels cause pharyngeal pumping defects in C. elegans."

Roberts B, Webb A, Clovis Y, Turner C

[MicroPubl Biol, 2016]

Pumps were stimulated with 10mM 5HT in M9 recorded as electropharyngeograms (EPGs) for 2 minutes in a NemaMetrix ScreenChip, and analyzed using NemAnalysis software (NemaMetrix). The null mutant strains kqt-1(aw3) and kqt-3 (aw1) were kindly donated by Dr. Aguan Wei (Wei et al., 2002) A) Pump frequency in kqt-1(aw3) animals was significantly lower than in N2s, while kqt-3(aw1) worms showed an increase in pump frequency (*p<0.05; ***p<0.01; 1-tailed Mann-Whitney U-test; n = 21-23 worms in each strain). B) Microfluidic EPG recordings show that pumping pattern in kqt-1(aw3) mutants is arrhythmic, with frequent drops in frequency. C) Overlay of first 50 pumps of recordings show that pump duration is higher in kqt-1(aw3) and kqt-3(aw1) animals than in N2s. Pumps are showed aligned on E spikes, which occur when the pharynx is fully contracted. D) Duration histogram illustrating the probability of occurrence of inter-pump interval (E to E duration) for each mutant strain. Histograms were binned to 4 ms width and normalized to reach an area underneath the curve equal to 1 (duration 100% likelihood to occur). In kqt-1(aw3)) animals, the time between two pumps is significantly increased compared to N2s (p < 0.01).