A new Dol-P-Man:protein O-D-mannosyltransferase activity from Saccharomyces cerevisiae

The deletion of the protein mannosyltransferase 1 gene (PMT1)of Saccharomyces cerevisiae results in viable cells. O-Mannosylationof proteins is reduced to about half of the value in comparisonto wild-type cells. In order to distinguish between the thePMT1 gene product (= Pmt1p) and residual transferase activity,an in vitro assay to measure Dol-P-Man:protein mannosyltransferaseactivity in cells deleted for PMT1 has been developed. The transferaseactivity of these cells exhibits a pH optimum of 6.5 as comparedto pH 7.5 for Pmt1p. The K_$$$ value of the residual enzyme activityfor the hexapeptide YNPTSV is 7 times higher than that of Pmt1pand shows a clear preference for the seryl/residue. Differencesin substrate affinities as well as in seryl/threonyl preferencebetween the two enzymes, however, depend on the specific sequenceof the peptides used in the enzyme assay. The new enzyme activityshows a significantly lower thermal stability as compared toPmt1p. glycoprotein O-glycosylation mannosyltranferase Saccharomyces cerevisiae     

Mapping of transfer RNA genes on tobacco chloroplast DNA

Tobacco chloroplast tRNAs have been purified by two-dimensional polyacrylamide gel electrophoresis, identified by aminoacylation, labelled at their 3-end and hybridized to tobacco chloroplast DNA restriction fragments, in order to establish a tRNA gene map. These hybridization studies have revealed the localization of at least seven genes in each inverted repeat region, a minimum of 22 tRNA genes in the large single copy region and one tRNA gene in the small single copy region. Comparison of the tobacco chloroplast tRNA gene map to that of maize shows many similarities, but also some differences suggesting that DNA sequence rearrangements have occurred in the chloroplast genome during evolution.     

The beta chorionic gonadotropin-beta luteinizing gene cluster maps to human chromosome 19

Summary We used a cloned human cDNA probe homologous to the placenta chorionic gonadotropin subunit (CGB) and to the pituitary luteinizing hormone subunit (LHB) and Southern blotting techniques to analyse DNA from a series of rodent x human somatic cell hybrids for the presence of specific gonadotropin subunit related sequences. Our results provide evidence for the assignment and linkage of the eight genes (or pseudogenes) coding for the subunit of these glycoprotein hormones to chromosome 19. Moreover, we observed a strict concordance between the permissivity of mouse x man hybrid cells to enteroviruses (which is linked to the presence of specific cell receptors encoded by human chromosome 19) and the presence of CGB and LHB related sequences, thus confirming the localization of the structural genes for the subunits on chromosome 19.This work was supported in part by INSERM grants CRL 81 1041 and by MRC grant MT 4860     

Assignment of the gene for uroporphyrinogen decarboxylase to human chromosome 1 by somatic cell hybridization and specific enzyme immunoassay

Summary A specific enzyme immunoassay of uroporphyrinogen decarboxylase was developed and applied to the detection of the human enzyme in man-rodent somatic cell hybrids. This method allowed to assign the gene for uroporphyrinogen decarboxylase to human chromosome 1.     

The effect of trisomy 21 on the patterns of polypeptide synthesis in human fibroblasts.

In addition to direct gene dosage effects, the deleterious phenotypic consequences of aneuploidy may result from secondary regulatory effects on the production and degradation of gene products coded for by other chromosomes. In an initial test of the hypothesis that extensive secondary effects play an important role in the phenotypic consequences of aneuploidy, we have used two-dimensional gel electrophoresis with radioautography to look for such secondary effects among the polypeptides synthesized by human fibroblasts grown in vitro. The polypeptide patterns of fibroblast strains from four trisomy 21 subjects and one trisomy 21/normal mosaic were compared to those from five matched normal subjects. Of approximately 850 polypeptides visualized, only four show a pattern of variation which may be related to trisomy 21. Additional differences in polypeptide concentrations were found among the strains, attributable to genetic heterogeneity between donor individuals and differences in tissue of origin. These results indicate that, at least in fibroblasts in vitro, trisomy 21 does not cause major regulatory changes in the rates of production and degradation of a large number of polypeptides.     

Biochemical evidence for the non-inactivation of the steroid sulfatase locus in human placenta and fibroblasts

Summary Steroid sulfatase activities are significantly higher in placentas obtained after the birth of girls than after the birth of boys, and also in female fibroblasts compared to male strains. This constitutes biochemical evidence for the non-inactivation of the X-linked sulfatase locus. No hydrolytic activity is found in the fibroblasts of ichthyotic boys. Heterozygosity is demonstrated in the fibroblasts of the four mothers studied, as they have steroid sulfatase activity of less or equivalent to the normal male value.     

Biological effects of long-term exposure of rats to 970-MHz radiofrequency radiation

Rats (N = 16) exposed individually in circularly polarized waveguides to 970-MHz electromagnetic radiation (SAR=2.5 mW/g, 22 h daily for 70 consecutive days) had significantly higher serum levels of triglycerides, albumin, and total protein compared with sham-irradiated controls. No difference was observed in the weights, hematologic profile, or in vitro lymphocyte responses to mitogens between these two groups. The higher serum levels of triglycerides in radiofrequency-radiation-exposed rats suggest a non-specific stress reaction.     

Localisation régionale des gènes humains IDHS,MDHS, PGK, α-GAL,G6PD par l'hybridation cellulaire interspécifique

Summary 22 independent man-hamster (HGPRT^–) hybrids using male human cells with balanced reciprocal translocation t(X;2)(p22;q32) were analysed for human genes localized on chromosome 2 (IDH_S, MDH_S), on chromosome X (PGK, GAL, G6PD) and for the different chromosomes in relation with the balanced reciprocal translocation (chr.2, chr.2q^–, chr.Xp⁺).The following results were obtained:The chromosomes 2 and 2q^– are absent in the 22 hybrids.In 9 hybrids, the absence of MDH_S in spite of the presence of the chromosome Xp⁺ indicates that the gene for MDH_S is not localized on this chromosome (or that the gene for MDH_S is not on the segment 2q32-2qter translocated on X).In 14 hybrids, the three markers of X (PGK, GAL, G6PD) and IDH_S are expressed in the presence of the chromosome Xp⁺. This result indicates that the genes for these markers are on Xp⁺ or that the genes PGK, GAL, G6PD are on X without the Xp22-Xter segment, translocated on the chr.2, and that the gene for IDH_S is on the 2q32-2qter segment translocated on X.In 8 hybrids, in the absence of the intact chromosome Xp⁺, the higher percentage of the presence of G6PD (7 hybrids) and the lower percentage of the presence of IDH_S (3 hybrids) are explained by the fact that these hybrids selected in HAT medium had to retain a segment of Xp⁺ bearing the human gene HGPRT. G6PD appeared very close to HGPRT and IDH_S very distant from HGPRT.The study of the different correlations between the presence and the absence of these four markers on Xp⁺ in the different hybrids indicates the following order on the chromosome Xp⁺ from p to q: IDH_s — PGK — GAL — G6PD.

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Groupe INSERM: Directeur J. Frézal

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Groupe CNRS, ER, 149: Directeur J. de Grouchy     

A tumor-cell-agglutinating lectin in snail mucus from Arion lusitanicus (MAB) and Arion empiricorum (Fér.)

A lectin which agglutinates Zajdela hepatoma cells; rat red cells and lymphocytes, but no normal rat liver cells, was detected in the mucus, yielded by simple saline extraction, of the two snail species Arion empiricorum (Fér.) and Arion lusitanicus (MAB). The agglutination spectrum involves also human erythrocytes and red cells of several animal species.