Purification and properties of the guanine nucleotide exchange factor (GEF) from HeLa cells and its role in the initiation of protein synthesis

A guanine nucleotide exchange factor (GEF), catalyzing the exchange of GDP bound to initiation factor eIF-2 for GTP, has been isolated from S3 HeLa cells as the eIF-2 X GEF complex and extensively purified by procedures originally developed for purification of GEF from rabbit reticulocytes. The HeLa cell factor resembles rabbit reticulocyte eIF-2 X GEF in polypeptide composition, catalytic activity, and inactivation by alpha-phosphorylated eIF-2.     

Mitochondrial DNA evolution in theobscura species subgroup ofDrosophila

Summary Mitochondrial DNA (mtDNA) restriction site maps for nine species of theDrosophila obscura subgroup and forDrosophila melanogaster were established. Taking into account all restriction enzymes (12) and strains (45) analyzed, a total of 105 different sites were detected, which corresponds to a sample of 3.49% of the mtDNA genome. Based on nucleotide divergences, two phylogenetic trees were constructed assuming either constant or variable rates of evolution. Both methods led to the same relationships. Five differentiated clusters were found for theobscura subgroup species, one Nearctic, represented byDrosophila pseudoobscura, and four Palearctic, two grouping the related triads of speciesDrosophila subobscura, Drosophila madeirensis, Drosophila guanche, andDrosophila ambigua, Drosophila obscura, Drosophila subsilvestris, and two more represented by one species each,Drosophila bifasciata, andDrosophila tristis. The different Palearctic clusters are as distant between themselves as with the Nearctic one. For the related speciesD. subobscura, D. madeirensis, andD. guanche, the pairD. subobscura-D. madeirensis is the closest one. The relationships found by nucleotide divergence were confirmed by differences in mitochondrial genome size, with related species sharing similar genome lengths and differing from the distant ones. The total mtDNA size range for theobscura subgroup species was from 15.5 kb forD. pseudoobscura to 17.1 forD. tristis.     

Assignment of human aldolase C gene to chromosome 17, region cen→q21.1

Summary The mapping of the gene coding for human aldolase C has been studied using a specific cDNA probe and genomic blots from a panel of human-hamster somatic cell hybrids. The results show that the aldolase C gene is on chromosome 17. In situ experiments have restricted the mapping to the region 17cenq21.1. Using the same panel of human-hamster somatic cell hybrids, we have confirmed the localization of aldolase A and B on chromosomes 16 and 9, respectively.     

A human alphoid DNA clone from the EcoRI dimeric family: Genomic and internal organization and chromosomal assignment

We isolated an alpha satellite DNA clone (pC1.8), 17 kb long, which is composed exclusively of tandemly repeated 340-bp EcoRI fragments. Hybridization studies using 37 random EcoRI dimers subcloned from pC1.8 showed that they are heterogeneous. The sequence of 5 dimers, 3 of them adjacent, confirmed this observation and showed that the heterogeneity is more accentuated among the second monomers. The chromosomal assignment under high stringency conditions showed that this alphoid subset is located on chromosomes 1, 5, and 19. No conditions that eliminate the hybridization on any one of those chromosomes were found. This suggests that, in contrast to many other chromosome-specific alpha satellite subsets, the single chromosome subsets of this family are virtually indistinguishable by hybridization techniques.     

Colocalization of the gene for nephrogenic diabetes insipidus (DIR) and the vasopressin type 2 receptor gene (AVPR2) in the Xq28 region

The gene for nephrogenic diabetes insipidus (DIR) and the vasopressin type 2 receptor gene (AVPR2) have both been localized in the Xqter region by genetic mapping and functional expression studies, respectively. In this paper genetic evidence that the DIR locus is localized distal to the DXS305 locus and that the functional gene for the V2 receptor is localized between the markers DXS269 and F8 is presented. These further refinements in the localization of both genes strengthen the assumption that both genes are identical and provide a rationale for cloning the gene by reversed genetics strategies.     

A diterpenoid of the atis-16-ene class from Elaeoselinum foetidum

A new diterpenoid has been isolated from the root of Elaeoselinum foetidum. Its structure was established as ent-15α-senecioxy-atis-16-en-19-oic acid mainly by ¹H NMR ¹³C NMR spectroscopic studies of its methyl ester derivative.