We report gene targeting via homologous recombination in zebrafish. We co-injected fertilized eggs with transcription activator-like effector nuclease mRNAs and a donor vector with long homologous arms targeting the tyrosine hydroxylase (th) locus, and we observed effective gene modification that was transmitted through the germ line. We also successfully targeted two additional genes. Homologous recombination in zebrafish with a dsDNA donor expands the utility of this model organism.

The main protease (M pro ) of severe acute respiratory syndrome coronavirus (SARS-CoV) plays an essential role in the extensive proteolytic processing of the viral polyproteins (pp1a and pp1ab), and it is an important target for anti-SARS drug development. It was found that SARS-CoV M pro exists in solution as an equilibrium of both monomeric and dimeric forms, and the dimeric form is the enzymatically active form. However, the mechanism of SARS-CoV M pro dimerization, especially the roles of its N-terminal seven residues (N-finger) and its unique C-terminal domain in the dimerization, remain unclear. Here we report that the SARS-CoV M pro C-terminal domain alone (residues 187 to 306; M pro -C) is produced in Escherichia coli in both monomeric and dimeric forms, and no exchange could be observed between them at room temperature. The M pro -C dimer has a novel dimerization interface. Meanwhile, the N-finger deletion mutant of SARS-CoV M pro also exists as both a stable monomer and a stable dimer, and the dimer is formed through the same C-terminal-domain interaction as that in the M pro -C dimer. However, no C-terminal domain-mediated dimerization form can be detected for wild-type SARS-CoV M pro . Our study results help to clarify previously published controversial claims about the role of the N-finger in SARSCoV M pro dimerization. Apparently, without the N-finger, SARS-CoV M pro can no longer retain the active dimer structure; instead, it can form a new type of dimer which is inactive. Therefore, the N-finger of SARS-CoV M pro is not only critical for its dimerization but also essential for the enzyme to form the enzymatically active dimer.

Shape-directed self-assembly of unique gold nanoarrows into supercrystals with unprecedented architectures is realized.

BackgroundGenome-wide duplication is ubiquitous during diversification of the angiosperms, and gene duplication is one of the most important mechanisms for evolutionary novelties. As an indicator of functional evolution, the divergence of expression patterns following duplication events has drawn great attention in recent years. Using large-scale whole-genome microarray data, we systematically analyzed expression divergence patterns of rice genes from block, tandem and dispersed duplications.ResultsWe found a significant difference in expression divergence patterns for the three types of duplicated gene pairs. Expression correlation is significantly higher for gene pairs from block and tandem duplications than those from dispersed duplications. Furthermore, a significant correlation was observed between the expression divergence and the synonymous substitution rate which is an approximate proxy of divergence time. Thus, both duplication types and divergence time influence the difference in expression divergence. Using a linear model, we investigated the influence of these two variables and found that the difference in expression divergence between block and dispersed duplicates is attributed largely to their different divergence time. In addition, the difference in expression divergence between tandem and the other two types of duplicates is attributed to both divergence time and duplication type.ConclusionConsistent with previous studies on Arabidopsis, our results revealed a significant difference in expression divergence between the types of duplicated genes and a significant correlation between expression divergence and synonymous substitution rate. We found that the attribution of duplication mode to the expression divergence implies a different evolutionary course of duplicated genes.