The zebrafish Hairy/Enhancer-of-split-related gene her6 is segmentally expressed during the early development of hindbrain and somites

Several vertebrate genes of the Hairy/Enhancer-of-split (HES) family are involved in paraxial mesoderm segmentation and intersomitic boundary establishment/maintenance. Here, we show that the zebrafish hairy-related gene, her6, highly homologous to the mammalian and chicken HES-1 genes, is expressed in the posterior part of each segmented somite and in stripes in the anterior presomitic mesoderm (PSM), and also in a dynamic, segmentally restricted pattern during hindbrain segmentation, with all rhombomeres expressing her6 at different time points and at different levels.     

Localization of the Drosophila MAGUK protein Polychaetoid is controlled by alternative splicing

The Drosophila membrane-associated guanylate kinase (MAGUK) protein Polychaetoid (Pyd) is required for dorsal closure of the embryo, sensory organ patterning, and cell fate specification in the developing eye. We demonstrate that pyd is alternatively spliced resulting in two isoforms that differ by the presence or absence of exon 6. To determine the role of alternative splicing in Pyd function, we generated antibodies specific for each isoform. We find that the exon 6⁺ form of Pyd is localized at adherens junctions of embryonic and imaginal epithelia, while the exon 6⁻ form is distributed broadly along the lateral membrane. These results suggest that localization of Pyd is controlled by alternative splicing and raise the possibility that exon 6 represents a distinct protein–protein interaction domain.     

A repressor element in the 5'-untranslated region of human Pax5 exon 1A

Five members of the RecQ helicase family, RECQL, WRN, BLM, RTS and RECQL5, have been found in human and three of them (WRN, BLM and RTS) were disclosed to be the genes responsible for Werner, Bloom and Rothmund–Thomson syndromes, respectively. RECQL5 (RecQ helicase protein-like 5) was isolated as the fifth member of the family in humans through a search of homologous expressed sequence tags. The gene is expressed with at least three alternative splicing products, , β and γ. Here, we isolated mouse RECQL5β and determined the DNA sequence of full-length cDNA as well as the genome organization and chromosome locus. The mouse RECQL5β gene consists of 2949 bp coding 982 amino acid residues. Comparison of amino acid sequence among human (Homo sapiens), mouse (Mus musculus), Drosophila melanogaster and Caenorhabditis elegans RECQL5β homologs revealed three portions of highly conserved regions in addition to the helicase domain. Nineteen exons are dispersed over 40 kbp in the genome and all of the acceptor and donor sites for the splicing of each exon conform to the GT/AG rule. The gene is localized to the mouse chromosome 11E2, which has a syntenic relation to human 17q25.2-q25.3 where human RECQL5β exists. Our genetic characterizations of the mouse RECQL5β gene will contribute to functional studies on the RECQL5β products.     

The pentatricopeptide repeat protein EMB1270 interacts with CFM2 to splice specific group II introns in Arabidopsis chloroplasts

Chloroplast biogenesis requires the coordinated expression of chloroplast and nuclear genes. Here, we show that EMB1270, a plastid-localized pentatricopeptide repeat (PPR) protein, is required for chloroplast biogenesis in Arabidopsis thaliana. Knockout of EMB1270 led to embryo arrest, whereas a mild knockdown mutant of EMB1270 displayed a virescent phenotype. Almost no photosynthetic proteins accumulated in the albino emb1270 knockout mutant. By contrast, in the emb1270 knockdown mutant, the levels of ClpP1 and photosystem I (PSI) subunits were significantly reduced, whereas the levels of photosystem II (PSII) subunits were normal. Furthermore, the splicing efficiencies of the clpP1.2, ycf3.1, ndhA, and ndhB plastid introns were dramatically reduced in both emb1270 mutants. RNA immunoprecipitation revealed that EMB1270 associated with these introns in vivo. In an RNA electrophoretic mobility shift assay (REMSA), a truncated EMB1270 protein containing the 11 N-terminal PPR motifs bound to the predicted sequences of the clpP1.2, ycf3.1, and ndhA introns. In addition, EMB1270 specifically interacted with CRM Family Member 2 (CFM2). Given that CFM2 is known to be required for splicing the same plastid RNAs, our results suggest that EMB1270 associates with CFM2 to facilitate the splicing of specific group II introns in Arabidopsis.