Conserved chromatin and repetitive patterns reveal slow genome evolution in frogs.

Frogs are an ecologically diverse and phylogenetically ancient group of anuran amphibians that include important vertebrate cell and developmental model systems, notably the genus Xenopus. Here we report a high-quality reference genome sequence for the western clawed frog, Xenopus tropicalis, along with draft chromosome-scale sequences of three distantly related emerging model frog species, Eleutherodactylus coqui, Engystomops pustulosus, and Hymenochirus boettgeri. Frog chromosomes have remained remarkably stable since the Mesozoic Era, with limited Robertsonian (i.

Regulation of ubiquitin chain initiation to control the timing of substrate degradation.

Processive reactions, such as transcription or translation, often proceed through distinct initiation and elongation phases. The processive formation of polymeric ubiquitin chains can accordingly be catalyzed by specialized initiating and elongating E2 enzymes, but the functional significance for this division of labor has remained unclear. Here, we have identified sequence motifs in several substrates of the anaphase-promoting complex (APC/C) that are required for efficient chain initiation by its E2 Ube2C.

Wnt/beta-catenin and noncanonical Wnt signaling interact in tissue evagination in the simple eumetazoan Hydra.

In and evaginations of 2D cell sheets are major shape generating processes in animal development. They result from directed movement and intercalation of polarized cells associated with cell shape changes. Work on several bilaterian model organisms has emphasized the role of noncanonical Wnt signaling in cell polarization and movement.

Mechanism of ubiquitin-chain formation by the human anaphase-promoting complex.

The anaphase-promoting complex (APC/C) orchestrates progression through mitosis by decorating cell-cycle regulators with ubiquitin chains. To nucleate chains, the APC/C links ubiquitin to a lysine in substrates, but to elongate chains it modifies lysine residues in attached ubiquitin moieties. The mechanism enabling the APC/C, and ubiquitin ligases in general, to switch from lysine residues in substrates to specific ones in ubiquitin remains poorly understood.

The exceptional stem cell system of Macrostomum lignano: screening for gene expression and studying cell proliferation by hydroxyurea treatment and irradiation.

Background: Flatworms are characterized by an outstanding stem cell system. These stem cells (neoblasts) can give rise to all cell types including germ cells and power the exceptional regenerative capacity of many flatworm species. Macrostomum lignano is an emerging model system to study stem cell biology of flatworms.

HvJNK, a Hydra member of the c-Jun NH2-terminal kinase gene family, is expressed during nematocyte differentiation.

C-jun NH(2)-terminal kinases (JNKs) represent a subgroup of mitogen-activated protein kinases (MAPKs). MAPK pathways are important regulators of cell proliferation, apoptosis, and gene expression throughout higher metazoans. We report here the characterization of a highly conserved Hydra JNK orthologue (HvJNK) that exhibits amino acid sequence identity of 61% as compared with human JNK1alpha.