Close linkage of prd and rel genes in Escherichia coli K-12

Summary The prd gene, the mutant allele of which permits growth of E. coli on 1,2-propanediol as sole carbon source, has been located by transduction very close to the rel (RNA control) gene. This close linkage provides a convenient means for the inter-strain transfer of rel.This work was supported in part by the Australian Meat Research Committee.     

A chromosomal linkage map of Azotobacter vinelandii

Summary A chromosomal map of Azotobacter vinelandii strain UW was constructed. The map was based on measures of cotransfer of various markers mediated by plasmids R68.45 and pJB3JI, on results obtained from conjugal experiments with R-primes, and on recombinants obtained by chromosomal transfer mediated by RP4/Tn5-Mob.     

Drosophila resistance genes to parasitoids: chromosomal location and linkage analysis

Insect hosts can survive infection by parasitoids using the encapsulation phenomenon. In Drosophila melanogaster the abilities to encapsulate the wasp species Leptopilina boulardi and Asobara tabida each involve one major gene. Both resistance genes have been precisely localized on the second chromosome, 35 centimorgans apart. This result clearly demonstrates the involvement of at least two separate genetic systems in Drosophila resistance to parasitoid wasps. The resistance genes to L. boulardi and A. tabida are not clustered as opposed to many plant resistance genes to pathogens cloned to date.     

Hypomethylation and expression of pepsinogen A genes in the fundic mucosa of human stomach

We have examined the correlation between the extents of methylation and expression of pepsinogen A genes in normal human tissues. Expression of pepsinogen A mRNA was detected only in the fundic mucosa of the stomach and both CCGG and GCGC sites in the genes region were less methylated in the fundic mucosa than in other non-expressing tissues. Thus, there was an inverse correlation between the extents of methylation and expression of pepsinogen A genes and the role of DNA methylation in the regulation of pepsinogen A genes expression during normal differentiation was suggested.     

Subfamily of submaxillary gland-specific Mup genes: chromosomal linkage and sequence comparison with liver-specific Mup genes

Mouse major urinary proteins (MUPs) are encoded by a family of ca. 35 genes that are expressed in a tissue-specific manner in several secretory organs; in the liver, in the submaxillary, sublingual, parotid and lachrymal glands, and in the skin sebaceous glands. In this paper we describe the isolation of a Mup gene, Mup-1.5a, which is expressed predominantly in the submaxillary gland of BALB/c mice. We show that Mup-1.5a is a member of a subfamily consisting of two closely related genes, both of which are closely linked to the Mup-1 locus on mouse chromosome 4. Mup-1 is the locus of a class of Mup genes (Group 1) expressed in the liver. The complete nucleotide sequence of Mup-1.5a has been determined, and was compared to a previously sequenced Group 1 Mup gene. The comparison shows that the differentially expressed Mup genes are uniformly divergent in exons, introns and in their flanking sequences. The regions of homology extend at least 5 kb into the 5' flanking region of Mup genes.     

Close physical linkage of the genes encoding the pNR-2/pS2 protein and human spasmolytic protein (hSP)

Trefoil proteins contain a conserved domain of distinctive structure. Three human trefoil proteins have been described to date of which the human spasmolytic polypeptide (hSP) and pNR-2/pS2 proteins have a similar pattern of expression in normal tissues. The genes encoding these two proteins were isolated from a human DNA library. Preliminary experiments suggested that some recombinants contained both genes. Southern hybridisation showed that all the recombinants were derived from a single stretch of DNA spanning 45 kb and suggested that the hSP gene was located downstream of the pNR-2/pS2 gene. Further experiments demonstrated that the two genes are transcribed in the same direction and that the distance between the 3′ end of the pNR-2/pS2 gene and the 5′ end of the hSP gene is 12.5 kb. The close linkage of these two genes is evidence that they have evolved by gene duplication and that their similar pattern of expression in normal tissues could result from the retention of common regulatory elements. Received: 3 June 1996 / Revised: 13 September 1996     

Probable genetic linkage between a locus for human urinary pepsinogen and the HL-A loci.

The genetic basis of familial variation in the relative intensities of human urinary pepsinogen isozymes is not completely clear from family studies. An investigation of the linkage relationships of pepsinogen isozyme 5, considering only segregation for the presence or absence of Pg 5, yields a peak lod score of 4.1 at theta = .1 for linkage with HL-A1 or HL-A2. Added to data from segregation interpreted according to a scheme proposed for the inheritance of intensity differences in Pg 5, the peak lod score becomes 3.0 at theta = .2. Data derived from the segregation of pepsinogen isozyme 4, possibly determined by an allele to that controlling the presence or absence of Pg 5, further reduces the total lod score at theta = .2 to 2.9. The results indicate probable linkage between a locus for urinary pepsinogen and the HL-A loci, but are insufficient to permit any conclusion concerning possible heterogeneity in the linkage relationships of Pg 4 and Pg 5 to HL-A.     

Intergeneric complementation by Agrobacterium tumefaciens chromosomal genes and its potential use for linkage mapping

The IncP1 type plasmids pULB113 (RP4:: mini-Mu) and pJB3JI were used for chromosome mobilization and R prime formation in Agrobacterium tumefaciens. With pULB113, R primes were selected for complementation of an auxotrophic marker in an Alcaligenes eutrophus recipient strain. With pJB3JI, R primes containing the Agrobacterium chromosomal virulence region chv, inactivated by a Tn5 insertion, were constructed. Selection was for kanamycin resistance in E. coli strain GV1000. Complementation tests were performed in auxotrophic A. tumefaciens, A. eutrophus and Pseudomonas fluorescens strains. This allowed us to map 9 loci, including the chv loci, in a region accounting for about 10% of the Agrobacterium chromosome.     

Close linkage of genes encoding glutamine synthetases I and II in Frankia alni CpI1.

Frankia alni CpI1 has two glutamine synthetases (GSs), GSI and GSII. The GSI gene (glnA) was isolated from a cosmid library of F. alni CpI1 DNA by heterologous probing with glnA from Streptomyces coelicolor. The glnA gene was shown to be located upstream of the GSII gene (glnII) by DNA-DNA hybridization. The nucleotide sequences of the 1,422-bp CpI1 glnA gene and of the 449-bp intervening region between glnA and glnII were determined, and the glnA amino acid sequence was deduced. In common with GSIs from other organisms, CpI1 GSI contains five conserved regions near the active site and a conserved tyrosine at the adenylylation site. F. alni CpI1 glnA complemented the glutamine growth requirement of the Escherichia coli glnA deletion strain YMC11 but only when expressed from an E. coli lac promoter. While the functional significance of maintaining two GSs adjacent to one another remains unclear, this arrangement in F. alni provides support for the recently proposed origin of GSI and GSII as resulting from a gene duplication early in the evolution of life.     

Close linkage of genes encoding receptors for subgroups A and C of avian sarcoma/leucosis virus on chicken chromosome 28

Avian sarcoma and leucosis viruses (ASLV) are classified into six major subgroups (A to E and J) according to the properties of the viral envelope proteins and the usage of cellular receptors for virus entry. Subgroup A and B receptors are identified molecularly and their genomic positions TVA and TVB are mapped. The subgroup C receptor is unknown, its genomic locus TVC is reported to be genetically linked to TVA, which resides on chicken chromosome 28. In this study, we used two chicken inbred lines that carry different alleles coding for resistance (TVC(R) and sensitivity (TVC(S)) to infection by subgroup C viruses. A backross population of these lines was tested for susceptibility to subgroup C infection and genotyped for markers from chicken chromosome 28. We confirmed the close linkage between TVA and TVC loci. Further, we have described the position of TVC on chromosome 28 relative to markers from the consensus map of the chicken genome.     

Three parallel linkage groups of human acidic keratin genes.

Two regions of human genomic DNA, each containing several keratin genes, were isolated and partially sequenced. The keratin genes are inactive, having suffered deleterious mutations. Both regions contain at least four keratin genes arranged in a head-to-tail orientation including a pseudogene for keratin K#16. Within each segment there are two keratin genes in close linkage with only 1.5 kb of DNA between them. Sequence comparison of the two regions showed 98.9% identity in both the coding and the intronic segments of the pseudogenes. The pseudogenes show 94% identity to their functional counterparts. Southern hybridization analysis showed that the segments are paralogous, not allelic. The regions are products of two independent, recent duplication events. The first occurred approximately 24 million years ago, after the separation of primates from the rhesus/baboon line. The second is specific for the human lineage, having occurred approximately 3.8 million years ago. Analysis of the genomic DNAs of primates showed the presence of only one of the regions in the DNAs of gibbon and gorilla, while rhesus monkey and baboon were missing both copies. We conclude that the human keratin genes are still actively evolving, with new duplications having occurred as recently as after the separation of human and gorilla ancestors.     

Conjugational fertility and location of chloramphenicol biosynthesis genes on the chromosomal linkage map of Streptomyces venezuelae

In Streptomyces venezuelae fertility, defined as chromosomal gene recombination, was enhanced over 1000-fold when one parent in a biparental conjugational cross lacked the physically-undetected plasmid SVP1, as compared with crosses in which both parents carried SVP1. The existence of SVP1 and at least two other fertility plasmids, SVP2 and SVP3, was detected in S. venezuelae by 'lethal zygosis' elicited by a plasmid-plus mycelium in contact with a plasmid-minus mycelium. Conjugational crosses were used to construct a linkage map of S. venezuelae which was highly consistent with the map of analogous loci in S. coelicolor A3(2). A cluster of genes governing chloramphenicol biosynthesis was located near arg, cys and pdxB genes at a position roughly equivalent to the 1-2 o'clock region of the S. coelicolor A3(2) map.     

Close linkage of MEN2A with RBP3 locus in Japanese kindreds

Summary The gene responsible for multiple endocrine neoplasia type 2A (MEN2A) has recently been assigned to the pericentromeric region of chromsome 10 in European Caucasian kindreds by linkage analysis using a DNA marker, interstitial retinol-binding protein 3 (RBP3). We have found tight linkage between the MEN2A and RBP3 loci in Japanese MEN2A kindreds. The maximum lod score is 5.19 at a recombination fraction of 0.00. This result suggests that mutation of a certain gene close to RBP3 is responsible for MEN2A irrespective of ethnic backgrounds.