Interestingly, while some siRNA structural variants efficiently silence target gene expression, others show a reduction in or a complete lack of silencing activity.
From these results, we conclude that lack of silencing observed in the case of CenH3CID-lacI is actually the consequence of its failure to localise to the ectopic reporter sites.
As a matter of fact, silencing induced by NCenH3CID is strongly impaired when R-residues within B3 are replaced by alanine (A) (Figure 4D and 4F) or deleted (Figure 4E and 4F), and, concomitant to the lack of silencing, no ectopic αBubR1 signals are detected in these cases (Figure 5).
Ablation of DNMT3L largely prevented the passage-dependent silencing of retroviral transcription that occurs in the presence of DNMT3L, and this lack of silencing activity was associated with a failure to methylate the LTRs of the Mo-MLV42bp/GFP retrovirus.
Because the eso1 mutants do not relieve silencing at the pericentric regions, we speculate that the heterochromatic puffing associated with chromosomes in RBS may not be associated with lack of silencing.
However, we cannot rule out pleiotropic effects from a lack of silencing in repetitive regions or chromosome segregation defects known to occur in ∆ dim-5 (Lewis et al. 2010).
Even if these pairings are the result of chance instead of selection, it is possible that given the right physiological circumstances (e.g. high expression of the miRNAs, lack of silencing suppressor in the virus) these miRNAs would efficiently silence the predicted targets.
