Deep transcriptome profiling reveals limited conservation of A-to-I RNA editing in Xenopus.

BACKGROUND: Xenopus has served as a valuable model system for biomedical research over the past decades. Notably, ADAR was first detected in frog oocytes and embryos as an activity that unwinds RNA duplexes. However, the scope of A-to-I RNA editing by the ADAR enzymes in Xenopus remains underexplored. RESULTS: Here, we identify millions of editing events in Xenopus with high accuracy and systematically map the editome across developmental stages, adult organs, and species. We report diverse spatiotemporal patterns of editing with deamination activity highest in early embryogenesis before zygotic genome activation and in the ovary. Strikingly, editing events are poorly conserved across different Xenopus species. Even sites that are detected in both X. laevis and X. tropicalis show largely divergent editing levels or developmental profiles. In protein-coding regions, only a small subset of sites that are found mostly in the brain are well conserved between frogs and mammals. CONCLUSIONS: Collectively, our work provides fresh insights into ADAR activity in vertebrates and suggest that species-specific editing may play a role in each animal's unique physiology or environmental adaptation.

Inferring the contribution of small RNAs to changes in gene expression in response to stress.

A main strategy of bacteria adapting to environmental changes is the remodeling of their transcriptome. Changes in the transcript levels of specific genes are due to combined effects of various regulators, including small RNAs (sRNAs). sRNAs are post-transcriptional regulators of gene expression that mainly control translation, but also directly and indirectly affect the levels of their target transcripts. Yet, the relative contribution of an sRNA to the total change in the transcript level of a gene upon an environmental change has not been assessed. We present a design of differential gene expression analysis by RNA-seq that allows extracting the contribution of an sRNA to the total change in the transcript level of each gene in response to an environmental change by fitting a linear model to the data. We exemplify this for the sRNA RyhB in cells growing under iron limitation and show a variation among genes in the relative contribution of RyhB to the change in their transcript level upon iron limitation, from subtle to very substantial. Extracting the relative contribution of an sRNA to the total change in expression of genes is important for understanding the integration of regulation by sRNAs with other regulatory mechanisms in the cell.

CDB-a database for protein heterodimeric complexes.

Crystallographic structures of protein complexes are essential to develop proteomic and structural biology methods, as prediction of protein-protein interaction (PPI) sites and protein-protein docking. Such structures can aid the development of protein complexation inhibitors. Complex DataBase (CDB), accessible at www.jct-bioinfo.com/cdb/search, is a database web application for heterodimeric protein crystallographic complexes along with the crystallographic structures of each individual unbound protein. Direct access to crystallographic structures of protein complexes, along with provided annotations, can serve as starting point for constructing new experimental protein complexes sets of any type, for protein binding studies, and the development and evaluation of PPIs prediction methods.