The MAN antigens are non-lamin constituents of the nuclear lamina in vertebrate cells

The characterization of the human antiserum designated MAN has led to the identification of a subset of non-lamin proteins that are exclusively located at the nuclear periphery in all vertebrate cell types examined, from human to fish. Immunoreactive protein species were whown to comprise three major polypeptides of M _r 78000, 58000 and 40000. These antigens co-partitioned with the nuclear lamina during in situ isolation of nuclear matrices from lamin A/C-positive and-negative mammlian cells. Using double immunofluorescence, the spatial relationship of MAN antigens to type-A and type-B lamins was further examined throughout the cell cycle of lamin A/C-positive mammalian cells. In interphase HeLa and 3t3 cells, MAN antigens colocalized with both types of lamins at the periphery of the nucleus, but were absent from intranuclear foci of lamin B. As HeLa cells proceeded into mitosis, MAN antigens were seen to segregate from lamins A/C and coredistribute with lamin B. Lamins A/C disassembled during late prophase/early prometaphase and reassociated with chromatin in telophase/cytokinesis. In contrast, MAN antigens and lamin B dispersed late during prometaphase and reassembled on chromosomes in anaphase. Altogether, our data suggest that MAN antigens may play key functions in the maintenance of the structural integrity of the nuclear compartment in vertebrate cells.     

Are the characeae able to indicate the origin of groundwater in former river channels?

The macroscopic algae Characeae are usually assumed to occur in waterbodies supplied by groundwater with low phosphate content, but the indicative value of the species is seldom defined in bibliography. Former braided channels of the Rhône river are supplied with groundwater originating from the main channel (seepage) or from hillslope aquifer. The aim of the present paper was to determine if it possible to use the Characeae as indicators of physicochemical characteristies of water in order to assess the origin of groundwater supplying former river channels. Four former braided channels of the Rhône River colonized by Characeae were investigated, and the physico-chemical characteristics of i) the channels, ii) the groundwater and iii) the river were measured over a period of several months. Species are arranged along a gradient of conductivity, alkalinity, ammonium and phosphate content of the water. Charophyte species can indicate the origin of groundwater, either seepage or hillslope nutrient-poor aquifer, and integrate both the average value of the chemical parameter, and their variations. C. hispida occurs in a nutrient-poor channel mainly supplied by highly calcareous groundwater coming from hillslope aquifer. Chara major has requirements close to those of C. hispida, but is more tolerant to periodic inputs of nutrients. C. vulgaris and N. syncarpa both tolerate mesotrophic waters originating from both hillslope aquifer and seepage, and C. globularis is associated to a channel mainly supplied by mesotrophic to eutrophic river seepage.     

Two isoaccepting seryl tRNAs coded by separate mitochondrial genes in yeast

Summary In S. cerevisiae four isoacceptor mitochondrial tRNAs for serine have been separated by reversed phase chromatography. At least two of these species are products of different genes. In this work the deletion mapping technique has been used to locate two genes for tRNA^ser. The gene for tRNA^ser previously localized in the oli I region of the mitochondrial genome has been found to code for tRNA _ser ² , and another gene coding for tRNA _ser ¹ has been detected in the region where most of other tRNA genes are found. Results of fine mapping experiments allowed to localize this gene in the proximity of the gene for tRNA^arg.     

Structural polypeptides and products of late genes of bacteriophage Mu: Characterization and functional aspects

This paper describes the identification and functional role of late gene products of bacteriophage Mu, including an analysis of the structural proteins of the Mu virion.In vitro reconstitution of infectious phage particles has shown that four genes (E, D, I, J) control the formation of phage heads and that a cluster of eight genes (K, L, M, N, P, Q, R, S) controls the formation of phage tails.Sodium dodecyl sulphate/polyacrylamide gel electrophoresis of Mu polypeptides synthesized in Escherichia coli minicells infected by Mu phages carrying amber mutations in various late genes has resulted in the identification of the products of gene C (15.5 × 10³M_r); H (64 × 10³M_r); F (54 × 10³M_r); G (16 × 10³M_r); L (55 × 10³M_r); N (60 × 10³M_r); P (43 × 10³M_r) and S (56 × 10³M_r). Minicells infected with λpMu hybrid phages and deletion mutants of Mu were used to identify polypeptides encoded by the V-β region of the Mu genome. These are the products of genes V, W or R (41.5 × 10³M_r, and 45 × 10³M_r); U (20.5 × 10³M_r) and of genes located in the β region (24 × 10³M_r (gpgin) and 37 × 10³M_r (possibly gpmom)).Analytical separation of the proteins of the Mu virion revealed that it consists of a major head polypeptide with a molecular weight of 33 × 10³, a second head polypeptide of 54 × 10³ (gpF) and two major tail polypeptides with molecular weights of 55 × 10³ and 12.5 × 10³ (gpL and gpY, respectively). In addition, there are five minor components of the tail (including gpN, gpS and gpU) and approximately seven minor components of the head structure of the virion (including gpH).     

Mitochondrial and Nuclear Genes-Based Phylogeography of Arvicanthis niloticus (Murinae) and Sub-Saharan Open Habitats Pleistocene History

A phylogeographic study was conducted on the Nile grass rat, Arvicanthis niloticus, a rodent species that is tightly associated with open grasslands from the Sudano-Sahelian regions. Using one mitochondrial (cytochrome b) and one nuclear (intron 7 of Beta Fibrinogen) gene, robust patterns were retrieved that clearly show that (i) the species originated in East Africa concomitantly with expanding grasslands some 2 Ma, and (ii) four parapatric and genetically well-defined lineages differentiated essentially from East to West following Pleistocene bioclimatic cycles. This strongly points towards allopatric genetic divergence within savannah refuges during humid episodes, then dispersal during arid ones; secondary contact zones would have then stabilized around geographic barriers, namely, Niger River and Lake Chad basins. Our results pertinently add to those obtained for several other African rodent as well as non-rodent species that inhabit forests, humid zones, savannahs and deserts, all studies that now allow one to depict a more comprehensive picture of the Pleistocene history of the continent south of the Sahara. In particular, although their precise location remains to be determined, at least three Pleistocene refuges are identified within the West and Central African savannah biome.