Human viruses under attack by small inhibitory RNA
Several exciting recent publications have demonstrated that a newly discovered phenomenon coined as
RNA interference (RNAi) can be harnessed to inhibit replication of a wide variety of viruses in
cultured human cells effectively. These studies have generated optimism that RNAi might become a
valuable tool for fighting viral diseases such as hepatitis and AIDS.
One important factor leading to the idea of using RNA interference (RNAi) against human viruses was
the recent notion that posttranscriptional gene silencing (PTGS), a process known for many years to
play a key role in antiviral defence in plants, is in fact mediated by RNAi [1]. As expected of any
important antiviral defence mechanism, it has become apparent that plant viruses have generated
sophisticated molecular strategies to escape from RNAi-mediated inhibition, and plants in turn have
evolved to express their own countermeasures for blunting such escape strategies. The molecular
mechanism of RNAi was discovered, however, as a consequence of experiments designed to explain
certain paradoxical observations regarding inhibition of Caenorhabditis elegans gene expression by
antisense RNA.
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Cloning livestock: a return to embryonic cells
Restoring nuclear totipotency in differentiated somatic cells following nuclear transfer, to produce
healthy cloned animals, remains remarkable but highly inefficient and prone to epigenetic errors.
The high rates of mortality throughout development create serious animal welfare issues, which limit
the acceptability of somatic cloning. We anticipate a renaissance of embryonic cloning to alleviate
these problems. In animal breeding, improved genetic markers, correlated to specific livestock
production traits, will provide confidence in cloning selected embryos and their derivatives,
especially undifferentiated embryonic stem cells. This will enable rapid dissemination of the most
recent elite genotypes to avoid the genetic lag associated with cloning adults. For the production
of transgenic livestock, embryonic stem cells might also be beneficial, because they are more
amenable to precise genetic modifications and result in higher cloning efficiencies than somatic
cells in the mouse. We argue that for agricultural applications, embryonic cloning will ultimately
prove more useful than somatic cloning.
The first successful cloning of adult mammals [1] helped to overturn previous conceptions regarding
the restricted developmental plasticity of somatic cells, and is raising exciting prospects for
human regenerative medicine [2]. In addition, somatic cloning, coupled with genetic modification,
will better enable production of human therapeutics as well as xenograft tissues and organs from
livestock [3]. Opportunities for animal cloning and transgenesis in agriculture are more challenging
than biomedical applications because they require greater biological efficiency at reduced cost to
be economically viable. Another potentially difficult issue concerns consumer acceptance of the food
products resulting from this technology.
Kind Regards, Robert Karl Stonjek.
Kind Regards, Robert Karl Stonjek.