A tryptophan-rich peptide acts as a transcription activation domain

<p>Abstract</p> <p>Background</p> <p>Eukaryotic transcription activators normally consist of a sequence-specific DNA-binding domain (DBD) and a transcription activation domain (AD). While many sequence patterns and motifs have been defined for DBDs, ADs do not share easily recognizable motifs or structures.</p> <p>Results</p> <p>We report herein that the N-terminal domain of yeast valyl-tRNA synthetase can function as an AD when fused to a DNA-binding protein, LexA, and turn on reporter genes with distinct LexA-responsive promoters. The transcriptional activity was mainly attributed to a five-residue peptide, WYDWW, near the C-terminus of the N domain. Remarkably, the pentapeptide <it>per se </it>retained much of the transcriptional activity. Mutations which substituted tryptophan residues for both of the non-tryptophan residues in the pentapeptide (resulting in W₅) significantly enhanced its activity (~1.8-fold), while mutations which substituted aromatic residues with alanine residues severely impaired its activity. Accordingly, a much more active peptide, pentatryptophan (W₇), was produced, which elicited ~3-fold higher activity than that of the native pentapeptide and the N domain. Further study indicated that W₇mediates transcription activation through interacting with the general transcription factor, TFIIB.</p> <p>Conclusions</p> <p>Since W₇shares no sequence homology or features with any known transcription activators, it may represent a novel class of AD.</p

Structural and Content Diversity of Mitochondrial Genome in Beet: A Comparative Genomic Analysis

Despite their monophyletic origin, mitochondrial (mt) genomes of plants and animals have developed contrasted evolutionary paths over time. Animal mt genomes are generally small, compact, and exhibit high mutation rates, whereas plant mt genomes exhibit low mutation rates, little compactness, larger sizes, and highly rearranged structures. We present the (nearly) whole sequences of five new mt genomes in the Beta genus: four from Beta vulgaris and one from B. macrocarpa, a sister species belonging to the same Beta section. We pooled our results with two previously sequenced genomes of B. vulgaris and studied genome diversity at the species level with an emphasis on cytoplasmic male-sterilizing (CMS) genomes. We showed that, contrary to what was previously assumed, all three CMS genomes belong to a single sterile lineage. In addition, the CMSs seem to have undergone an acceleration of the rates of substitution and rearrangement. This study suggests that male sterility emergence might have been favored by faster rates of evolution, unless CMS itself caused faster evolution

The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella

The strange evolutionary history of plant mitochondrial tRNAs and their aminoacyl-tRNA synthetases

International audienceThe translation systems of plant mitochondria differ from those of other mitochon-dria in that they incorporate tRNAs of three different origins: native mitochondrial tRNAs, plastid tRNAs transcribed from plastid DNA insertions in mitochondrial DNA, and nuclearly encoded imported tRNAs. The complicated evolutionary history of the tRNA replacement events leading up to this situation is slowly being unrav-eled. Recent research on plant aminoacyl-tRNA synthetases is starting to reveal how the mitochondrial compartment can cope with this unusual mix of tRNAs and has uncovered an unprecedented degree of sharing of isoforms between compart-ments. Many plant aminoacyl-tRNA synthetases are dual targeted to two compart-ments, either cytosol/mitochondria or plastids/mitochondria. The molecular basis for some of these cases of dual targeting are described

Plant specific Preprotein and Amino Acid Transporter Proteins are required for tRNA import into mitochondria

International audienc