Control of sigma virus multiplication by the ref(2)P gene of Drosophila melanogaster: an in vivo study of the PB1 domain of Ref(2)P.

Ref(2)P has been described as one of the Drosophila proteins that interacts with the sigma virus cycle. We generated alleles to identify critical residues involved in the restrictive (inhibiting viral multiplication) or permissive (allowing viral multiplication) character of Ref(2)P. We demonstrate that permissive alleles increase the ability of the sigma virus to infect Drosophila when compared to null alleles and we confirm that restrictive alleles decrease this capacity. Moreover, we have created alleles unfunctional in viral cycling while functional for Ref(2)P fly functions. This type of allele had never been observed before and shows that fly- and virus-related activities of Ref(2)P are separable. The viral status of Ref(2)P variants is determined by the amino-terminal PB1 domain polymorphism. In addition, an isolated PB1 domain mimics virus-related functions even if it is similar to a loss of function toward fly-related activities. The evolutionary tree of the Ref(2)P PB1 domain that we could build on the basis of the natural allele sequences is in agreement with an evolution of PB1 domain due to successive transient selection waves.

Translation and fates of the gag protein of 1731, a Drosophila melanogaster retrotransposon.

An entire copy of 1731, a Drosophila melanogaster retrotransposon, was tagged by fusing in frame its putative gag gene with the reporter LacZ sequence. The high transfection efficiency of Drosophila virilis cells added to the absence of 1731 in their genome allowed, by combining histochemical staining and immunological detections, the demonstration of the translation of the 1731 gag gene. The gag protein is gathered in virus-like particles. Its occurrence in nuclei is consistent with a nuclear localization signal. The expression of the sense construction was inhibited by cotransfections with its antisense homologue.

Association between a 10 kb Pvu II restriction fragment of genomic DNA with the hemochromatosis gene.

This study concerns the association between the hemochromatosis susceptibility gene and a 10 kb Pvu II HLA-class I specific restriction fragment. Forty Pvu II fragments are detected after hybridization with A3 or B7 probes, and 20 among them are polymorphic. The 10 kb polymorphic Pvu II fragment correlates absolutely with the A3 serological allele and patients with hemochromatosis, heterozygous or homozygous for A3, have the 10 kb Pvu II band.

Correlation of class I DNA Pvu II restriction HLA gene fragments with serologic alleles.

Restriction enzyme site polymorphisms for Pvu II endonuclease are examined in a panel of DNAs isolated from peripheral blood lymphocytes of HLA-typed individuals. 21 polymorphic bands are detected from a total of 39 restriction fragments analyzed, only 9 of them corresponding to common variable morphs. Three polymorph fragments only correlate with known HLA-A and -B serologic alleles.

The molecular basis for the association between HLA-A3 and idiopathic haemochromatosis.

An association was found between idiopathic haemochromatosis and a 6.2-kb Bgl I genomic DNA fragment. This fragment constitutes a class I sequence which correlates with HLA-B3. The Bgl I fragment could represent a sequence in linkage disequilibrium with the haemochromatosis gene.

Polymorphism of HLA class I genes after restriction by endonucleases Eco RI, Eco RV and Hind III.

After electrophoresis and transfer onto a hybridization membrane, the restriction endonuclease fragments obtained were probed with a cDNA carrying the nucleotide sequence encoding a class I HLA gene. Polymorphism for presence or absence of various Eco RI and Eco RV and Hind III fragments was noted in a panel of unrelated Parisian people: frequent polymorphism was described for 2 Eco RI restriction fragments of sizes 16.5 and 7.7 kb, for 5 Eco RV restriction fragments of sizes 25, 20, 11.5, 7.8 and 4 kb, and for 3 Hind III restriction fragments of sizes 27.5, 23.5 and 4.7 kb. The French population studied is in Hardy-Weinberg equilibrium for the different variants described.

Analysis of base substitutions induced by ultraviolet radiation in Escherichia coli.

A system for determining the precise specificity of mutagens operating on Escherichia coli has been described, and the results for UV irradiation have been presented. Attempts to correlate the base pairs preferentially mutated by UV light with pyrimidine-pyrimidine sequences are discussed.

Correlation of nonsense sites in the lacI gene with specific codons in the nucleotide sequence.

Nonsense mutations derived from 90 different codons in the lacI gene of Escherichia coli have been correlated with the I gene nucleotide sequence. In over 80 cases the specific codon which generates the nonsense mutation can be identified. The sequence shows that 14-16 sites arise through tandem double base changes.

Molecular basis of base substitution hotspots in Escherichia coli.

In the lacI gene of Escherichia coli spontaneous base substituion hotspots occur at 5-methylcytosine residues. The hotspots disappear when the respective cytosines are not methylated. We suggest that the hotspots may result from the spontaneous deamination of 5-methylcytosine to thymine, which is not excised by the enzyme DNA-uracil glycosidase.