Hope Not Hype - Third World Network

136 Hope Not Hype
Transgene RNAs would be particularly prone to aberrancy…especially if they have nonplant
derived elements, because they may not have the precise structures necessary for efficient
interactions with the full complement of mRNA-binding proteins associated with most cellular
mRNAs. In addition, if transcription terminates prematurely or late, it would produce truly
aberrant RNAs. Premature or late termination of transgene transcription may be affected by
structural features of the transgene DNA or RNA or, as suggested many years ago, by DNA
methylation within the transcribed region (Herr et al., 2006, p. 14999).
There are numerous examples of signal amplification and the ability of the signal to
act infectiously. “Our findings support the hypothesis that siRNAs themselves or
intermediates induced by siRNAs could comprise silencing signals and are generated in a
self-amplifying fashion” (Klahre et al., 2002, p. 11981). “Notably, RNA silencing can
spread over the plants from one region to another, and RdRP has been proposed to have a
role in this ‘spread of silencing’” (Tang and Galili, 2004, p. 464). The most compelling
mechanisms for signal amplification refer to the regeneration of dsRNA molecules from
either fresh transcripts targeted by existing dsRNA molecules, or de novo amplification
by RdRP (Mello and Conte Jr., 2004).
[I]njection of dsRNA in a C. elegans hermaphrodite generates RNAi that can be stably
inherited to the F2 generation [indicating] that dsRNA acts catalytically and/or is replicated
by cellular proteins. The fact that RNAi resulting from the injection of dsRNA into worm
intestine or by the feeding of worms with bacteria expressing dsRNA are as equally efficient
as direct injection into the germline, indicates that RNAi can spread from cell to cell in
much the same way as gene silencing occurs in plants (Cogoni and Macino, 2000, p. 639).
It is worth, at this point, recalling the Protocol text:
“Modern biotechnology” means the application of:
a. In vitro nucleic acid techniques, including recombinant deoxyribonucleic acid (DNA) and
direct injection of nucleic acid into cells or organelles (emphasis added)…
The animals described above that were infected by dsRNA and not a DNA transgene,
passed the silencing trait throughout the cells of their own bodies and to their offspring for
two generations. So although in these cases the trait faded in later generations (Bernstein
et al., 2001), this material did transfer “a character or trait to…subsequent generations of
the organism” (HSNO Act s2).
Therefore, dsRNA-mediated gene silencing meets the description of traits determined
by genetic material. These traits are dependent upon DNA methylation, chromatin
modification or the continued production of small dsRNA molecules, all of which constitute
different replication pathways for the trait (Matzke and Birchler, 2005). In all three cases,
there are examples where the DNA that is responsible for instigating the gene silencing
pathway is not necessary for its infectious spread or inheritance. Thus there is no question
that species of dsRNA can be critical components of genetic elements that either are