Does human genome editing reinforce or violate human dignity?

Germline genome editing is often disapproved of at the international policy level because of its possible threats to human dignity. However, from a critical perspective the relationship between this emerging technology and human dignity is relatively understudied. We explore the main principles that are referred to when ‘human dignity' is invoked in this context; namely, the link with eugenics, the idea of a common genetic heritage, the principle of equal birth and broader equality and justice concerns. Yet the concept is also used in favour of germline genome editing as it might improve the overall well-being of future generations. We conclude that dignity concerns do not justify a complete ban on safe heritable genome editing but should inform the implementation of side constraints to ensure that the value judgements about human traits that are inherent in this practice do not result in a diminished basic respect for those people affected by them.     

Is the Trypanosoma brucei REL1 RNA ligase specific for U-deletion RNA editing,and is the REL2 RNA ligase specific for U-insertion editing?

It was shown previously that the REL1 mitochondrial RNA ligase in Trypanosoma brucei was a vital gene and disruption affected RNA editing in vivo, whereas the REL2 RNA ligase gene could be down-regulated with no effect on cell growth or on RNA editing. We performed down-regulation of REL1 in procyclic T. brucei (midgut insect forms) by RNA interference and found a 40-50% inhibition of Cyb editing, which has only U-insertions, as well as a similar inhibition of ND7 editing, which has both U-insertions and U-deletions. In addition, both U-insertion and U-deletion in vitro pre-cleaved editing were inhibited to similar extents. We also found little if any effect of REL1 down-regulation on the sedimentation coefficient or abundance of the RNA ligase-containing L-complex (Aphasizhev, R., Aphasizheva, I., Nelson, R. E., Gao, G., Simpson, A. M., Kang, X., Falick, A. M., Sbicego, S., and Simpson, L. (2003) EMBO J. 22, 913-924), suggesting that the inhibition of both insertion and deletion editing was not due to a disruption of the L-complex. Together with the evidence that down-regulation of REL2 has no effect on cell growth or on RNA editing in vivo or in vitro, these data suggest that the REL1 RNA ligase may be active in vivo in both U-insertion and U-deletion editing. The in vivo biological role of REL2 remains obscure.     

p53: Guardian of the genome is also a suppressor of cell invasion?

Corresponds to: Mukhopadhyay UK, et al. p53 suppresses Src-induced podosome and rosette formation and cellular invasiveness through the upregulation of caldesmon. Mol Cell Biol 2009; 29:3088-98.     

Regulation of RNA function by aminoacylation and editing?

The chemical modification of nucleic acids is a ubiquitous phenomenon. Aminoacylation of tRNAs by aminoacyl-tRNA synthetases (ARSs) is a reaction essentially devoted to protein synthesis but it is used also as an emergency mechanism to recycle stalled ribosomes, and it is required for genome replication in some RNA viruses. In several aminoacyl-tRNA synthetases a correction mechanism known as editing is present to prevent aminoacylation errors. Genome data reveal a growing number of open reading frames encoding ARS-like proteins. This strongly suggests the existence of a widespread and nonconventional machinery for aminoacylation and editing. Here we review the different biological functions of aminoacylation and editing; also we propose an evolutionary scenario for the origin of these two reactions, and hypothesize an extant role for RNA charging and editing outside the genetic code.     

What is mtDNA good for in the study of primate evolution?

Recombinant DNA methods have made accessible the nuclear and organelle genomes of a vast array of plant and animal species.^1–3 Although evolutionary biologists and anthropologists have begun to exploit the full range of these methods, a disproportionate share of this research has centered on the mitochondrial genome (mtDNA). Because of its small size, conserved organization, mode of inheritance, and combination of rapidly and slowly evolving regions, mtDNA (Fig. 1) has appeared in many ways to be the ideal molecule for evolutionary studies of primates.^4,5 However, recent research on higher primates raises serious concerns about the utility of this molecule for evolutionary analysis in the absence of parallel data from the nuclear genome.^6–8 These studies suggest that we need to rethink our research strategies and define more clearly what mtDNA can be used for in the study of primate evolution.     

Nuclear domain ‘knock-in’ screen for the evaluation and identification of small molecule enhancers of CRISPR-based genome editing

CRISPR is a genome-editing platform that makes use of the bacterially-derived endonuclease Cas9 to introduce DNA double-strand breaks at precise locations in the genome using complementary guide RNAs. We developed a nuclear domain knock-in screen, whereby the insertion of a gene encoding the green fluorescent protein variant Clover is inserted by Cas9-mediated homology directed repair (HDR) within the first exon of genes that are required for the structural integrity of subnuclear domains such as the nuclear lamina and promyelocytic leukemia nuclear bodies (PML NBs). Using this approach, we compared strategies for enhancing CRISPR-mediated HDR, focusing on known genes and small molecules that impact non-homologous end joining (NHEJ) and homologous recombination (HR). Ultimately, we identified the small molecule RS-1 as a potent enhancer of CRISPR-based genome editing, enhancing HDR 3- to 6-fold depending on the locus and transfection method. We also characterized U2OS human osteosarcoma cells expressing Clover-tagged PML and demonstrate that this strategy generates cell lines with PML NBs that are structurally and functionally similar to bodies in the parental cell line. Thus, the nuclear domain knock-in screen that we describe provides a simple means of rapidly evaluating methods and small molecules that have the potential to enhance Cas9-mediated HDR.