Assignment of the human gamma-glutamyl transferase gene to the long arm of chromosome 22

Formation of human long intergenic non-coding RNA genes, pseudogenes, and protein genes: Ancestral sequences are key players

Pathways leading to formation of non-coding RNA and protein genes are varied and complex. We report finding a conserved repeat sequence present in human and chimpanzee genomes that appears to have originated from a common primate ancestor. This sequence is repeatedly copied in human chromosome 22 (chr22) low copy repeats (LCR22) or segmental duplications and forms twenty-one different genes, which include the human long intergenic non-coding RNA (lincRNA) family FAM230, a newly discovered lincRNA gene family termed conserved long intergenic non-coding RNAs (clincRNA), pseudogene families, as well as the gamma-glutamyltransferase (GGT) protein gene family and the RNA pseudogenes that originate from GGT sequences. Of particular interest are the GGT5 and USP18 protein genes that appear to have formed from an homologous repeat sequence that also forms the clincRNA gene family. The data point to ancestral DNA sequences, conserved through evolution and duplicated in humans by chromosomal repeat sequences that may serve as functional genomic elements in the development of diverse genes.

Metabolism of Glutathione S-Conjugates: Multiple Pathways

Many potentially toxic electrophilic xenobiotics and some endogenous compounds are detoxified by conversion to the corresponding glutathione S-conjugate, which is metabolized to the N-acetylcysteine S-conjugate (mercapturate) and excreted. Some mercapturate pathway components, however, are toxic. Bioactivation (toxification) may occur when the glutathione S-conjugate (or mercapturate) is converted to a cysteine S-conjugate that undergoes a β-lyase reaction. If the sulfhydryl-containing fragment produced in this reaction is reactive, toxicity may ensue. Some drugs and halogenated workplace/environmental contaminants are bioactivated by this mechanism. On the other hand, cysteine S-conjugate β-lyases occur in nature as a means of generating some biologically useful sulfhydryl-containing compounds.

Enzymes Involved in Processing Glutathione Conjugates

Many potentially toxic electrophiles react with glutathione to form glutathione S-conjugates in reactions catalyzed or enhanced by glutathione S-transferases. The glutathione S-conjugate is sequentially converted to the cysteinylglycine-, cysteine- and N-acetyl-cysteine S-conjugate (mercapturate). The mercapturate is generally more polar and water soluble than the parent electrophile and is readily excreted. Excretion of the mercapturate represents a detoxication mechanism. Some endogenous compounds, such as leukotrienes, prostaglandin (PG) A2, 15-deoxy-Δ^12,14-PGJ₂, and hydroxynonenal can also be metabolized to mercapturates and excreted. On occasion, however, formation of glutathione S- and cysteine S-conjugates are bioactivation events as the metabolites are mutagenic and/or cytotoxic. When the cysteine S-conjugate contains a strong electron-withdrawing group attached at the sulfur, it may be converted by cysteine S-conjugate β-lyases to pyruvate, ammonium and the original electrophile modified to contain an –SH group. If this modified electrophile is highly reactive then the enzymes of the mercapturate pathway together with the cysteine S-conjugate β-lyases constitute a bioactivation pathway. Some endogenous halogenated environmental contaminants and drugs are bioactivated by this mechanism. Recent studies suggest that coupling of enzymes of the mercapturate pathway to cysteine S-conjugate β-lyases may be more common in nature and more widespread in the metabolism of electrophilic xenobiotics than previously realized.

Characterization of a second gene encoding γ-glutamyl transpeptidase from Schizosaccharomyces pombe

The first gene encoding γ-glutamyl transpeptidase (GGTI) of the fission yeast has previously been characterized, and its expression was found to be regulated by various oxidative stress-inducing agents. In this work, a second gene, encoding GGTII, was cloned and characterized from the fission yeast Schizosaccharomyces pombe. The structural gene encoding GGTII was amplified from the genomic DNA of the fission yeast and ligated into the shuttle vector pRS316 to generate the recombinant plasmid pPHJ02. The determined sequence contains 3040 bp and is able to encode the putative 611 amino acid sequence of GGTII, which resembles the counterparts of Saccharomyces cerevisiae, Homo sapiens, Rattus norvegicus, and Escherichia coli. The DNA sequence also contains 940-bp upstream and 289-bp downstream regions of the GGTII gene. The Schizosaccharomyces pombe cells harboring plasmid pPHJ02 showed about 4-fold higher GGT activity in the exponential phase than the cells harboring the vector only, indicating that the cloned GGTII gene is functional. The S. pombe cells containing the cloned GGTII gene were found to contain higher levels of both intracellular glutathione (GSH) content and GSH uptake. The S. pombe cells harboring plasmid pPHJ02 showed increased survival on solid media containing hydrogen peroxide, diethylmaleate, aluminum chloride, cadmium chloride, or mercuric chloride. The GGTII mRNA level was significantly elevated by treatment with GSH-depleting diethylmaleate. These results imply that the S. pombe GGTII gene produces functional GGTII protein and is involved in the response to oxidative stresses in S. pombe cells.Key words: fission yeast, genomic DNA, γ-glutamyl transpeptidase, regulation, Schizosaccharomyces pombe, stress response.

Characterization and regulation of the γ-glutamyl transpeptidase gene from the fission yeast Schizosaccharomyces pombe

The structural gene for the putative γ-glutamyl transpeptidase (GGT) was isolated from the chromosomal DNA of the fission yeast Schizosaccharomyces pombe. The determined sequence contained 3324 bp and encoded the predicted 630 amino acid sequence of GGT, which resembles counterparts in Homo sapiens, Rattus norvegicus, Saccharomyces cerevisiae, and Escherichia coli. The S. pombe cells harboring the cloned GGT gene showed about twofold higher GGT activity in the exponential phase than the cells harboring the vector only, indicating that the cloned GGT gene was functional. To monitor the expression of the S. pombe GGT gene, we fused the fragment 1085 bp upstream of the cloned GGT gene into the promoterless β-galactosidase gene of the shuttle vector YEp367R to generate the fusion plasmid pGT98. The synthesis of β-galactosidase from the fusion plasmid in S. pombe cells was enhanced by treatments with NO-generating sodium nitroprusside (SN), L-buthionine-(S,R)-sulfoximine (BSO), and glycerol. The GGT mRNA level in the S. pombe cells was increased by SN and BSO. Involvement of Pap1 in the induction of the GGT gene by SN and BSO was observed.Key words: fission yeast, genomic DNA, γ-glutamyl transpeptidase, Pap1, regulation, Schizosaccharomyces pombe.

gamma-Glutamyl transpeptidase expression in Ewing's sarcoma cells: up-regulation by interferons

The genetic hallmark of Ewing's sarcoma family of tumours (ET) is the presence of the translocation t(11;22)(q24;q12), which creates the ET fusion gene, leading to cellular transformation. Five human gamma-glutamyl transpeptidase (gamma-GT) genes are located near the chromosomal translocation in ET. gamma-GT is a major enzyme involved in glutathione homoeostasis. Five human cell lines representative of primary or metastatic tumours were investigated to study whether gamma-GT alterations could occur at the chromosomal breaks and rearrangements in ET. As shown by enzymic assays and FACS analyses, all ET cell lines consistently expressed a functional gamma-GT which however did not discriminate steps of ET progression. As shown previously [Sancéau, Hiscott, Delattre and Wietzerbin (2000) Oncogene 19, 3372-3383], ET cells respond to the antiproliferative effects of interferons (IFNs) type I (alpha and beta) and to a much less degree to IFN type II (gamma). IFN-alpha and -beta arrested cells in the S-phase of the cell cycle. We found an enhancement of gamma-GT mRNA species with IFN-alpha and -beta by reverse transcriptase-PCR analyses. This is reflected by up-regulation of gamma-GT protein, which coincides with the increase in gamma-GT-specific enzymic activity. Similarly, IFNs up-regulate the levels of gamma-GT in another IFN-responsive B cell line. Whether this up-regulation of gamma-GT by IFNs is of physiological relevance to cell behaviour remains to be studied.

gamma-Glutamyl transpeptidase: catalytic mechanism and gene expression

The gamma-glutamyl transpeptidases are key enzymes in the so-called gamma-glutamyl cycle involving glutathione synthesis, the recovery of its constituents, and in the transport of amino acids. This membrane-bound ectoenzyme thus serves to regulate glutathione synthesis. This chapter deals with the active site chemistry of gamma-glutamyl transpeptidase, including the role of side-chain groups on the light subunit as well as several serine residues in the catalytic process. Also considered are genomic studies indicating (a) the presence of a single gene in mouse and rat; (b) the occurrence of multiple genes in humans; (c) the involvement of multiple promoters for gene expression; and (d) how these multiple promoters may play a role in the tissue-specific expression of gamma-glutamyl transpeptidases.

Cloning and expression of a novel type (III) of human gamma-glutamyltransferase truncated mRNA

We report the characterization of a novel human gamma-glutamyltransferase mRNA type. This type III mRNA differs from type I and type II mRNAs previously described by several point mutations and the presence of an unspliced 81 bp intron in the open reading frame. Further, type III mRNAs are truncated ones and are tissue and pathology specifically expressed. In fact, type III mRNAs are present in human placenta, sigmoid, lung and in 50% of acute lymphoblastic leukemia blood cells but they are never found in healthy lymphocytes.

gamma-Glutamyl transpeptidase-cellular expression in populations of normal human mononuclear cells and patients suffering from leukemias

The expression of the ectoenzyme gamma-glutamyl transpeptidase (EC2.3.2.2., gamma GT) was investigated by flow cytometry on populations of peripheral blood mononuclear cells (PBMC) from healthy subjects and patients suffering from several types of leukemia before and under chemotherapy. In unstimulated PBMC, 28% of these cells were found to be gamma GT positive. The highest expression was measured on monocytes (CD14/gamma GT+ cells: 60%). Within the subsets of T lymphocytes (CD3/gamma GT+ cells: 18%) we saw no clear differences between CD4+ and CD8+ cells. B lymphocytes, NK cells, and activated cells showed low expressions (up to 10%). Treatment of PBMC with mitogens, alpha-IFN, IL-2, and GM-CSF did not affect the enzyme expression on normal mononuclear cells (MNC). However, a rapid increase of gamma GT+ cells was found in the presence of glutathione (GSH) and n-acetyl cysteine (nAC), particularly on monocytes, B cells, and NK cells. Comparing 40 healthy subjects and untreated patients suffering from leukemias, a significantly higher expression of gamma GT+ cells in the total MNC populations (B-CLL: 57%, CML: 62% gamma GT+ cells) was observed in B-chronic lymphocytic leukemia (B-CLL) and chronic myelogenous leukemia (CML), whereas other leukemias did not show clear differences. Most interestingly, the gamma GT expression was diminished in all populations of CML cells after 5 h of incubation in the presence of 10 units/ml IFN-alpha. These data suggest a possible protective role of gamma GT in MNC and a regulatory function of this enzyme in the development of CML.

Localization of a regulatory region on the 5'-untranslated region of human hepatoma HepG2 gamma-glutamyltransferase mRNA and response to dexamethasone and antisense oligonucleotide treatment

We are reporting the functional analysis of the 5'-untranslated region (5'UTR) of human hepatoma HepG2 gamma-glutamyltransferase (GGT) mRNA. Transient expression of hybrid GGT-luciferase reporter gene mutants in HepG2 shows that this 5'UTR acts as a tissue-specific translational enhancer. A domain of 173 bases containing a steroid hormone response element (HRE) is responsible for the enhancing effect, which can be amplified by addition of dexamethasone at 10(-6) M. Furthermore, the regulatory role of the 5'UTR is demonstrated by interaction with sense and antisense oligonucleotides.

Protease-catalyzed conversion of insulin-like growth factor-1 and interleukin-6 into high-molecular-mass species through the sequential action of hematopoietic surface-associated cathepsin G and gamma-glutamyl transpeptidase-related activities

Interleukin-6 (IL-6) and insulin-like growth-factor-1 (IGF-1) are cytokines produced by a variety of cells that act on a wide range of tissues, influencing cell growth and differentiation. Purified plasma membranes from human U937 monoblastic cells produced in vitro dimeric species of IL-6- and IGF-1-derived peptides through the sequential actions of surface-associated enzymes cathepsin G and transpeptidase activities. Cathepsin G degraded native unglycosylated IL-6 and IGF-1 molecules into 8-kDa and 7-kDa peptides respectively. Subsequent dimerisation of these intermediate forms into 16-kDa IL-6- and 14-kDa IGF-1-derived peptides was inhibited by acivicin and glutathione which are specific inhibitors of the standard cell-surface gamma-glutamyl transpeptidase (gamma-GT). However U937 plasma membranes, cleared of gamma-GT activity by immunoprecipitation with anti-gamma-GT and adsorption on protein-G-Sepharose, were still able to convert the intermediate forms of IL-6 and IGF-1 into dimers. Together, these observations indicate that the transpeptidase involved in the formation of the dimeric species of IL-6 and IGF-1 was related to, but distinct from, standard cell-surface gamma-GT. Cells of all hematopoietic lineages expressed gamma-GT-related activity. In contrast to the 16-kDa IL-6-derived peptide that did not retain growth-stimulating activity, the 14-kDa IGF-1 peptide was at least equipotent with native IGF-1 in the BALB/c 3T3 fibroblast DNA synthesis response. The N/O-glycosylated IL-6 was clearly as sensitive to cathepsin-G- and gamma-GT-related activities as the unglycosylated IL-6 from Escherichia coli, thus indicating that the sugar chains did not protect the cleavage sites of the two proteases on the IL-6 molecule. Our in vitro findings raise the possibility that similar proteases participate in the regulation of the catabolism of IL-6 and IGF-1 in vivo.

Human lung expresses unique gamma-glutamyl transpeptidase transcripts

gamma-Glutamyl transpeptidase (EC 2.3.2.2, gamma GT) is a membrane-bound ectoenzyme that plays an important role in the metabolism of glutathione. It is composed of two subunits, both of which are encoded by a common mRNA. We examined the expression of gamma GT in human lung tissue by Northern blot analysis and screening a cDNA library made from human lung poly(A)+ RNA. Our results show that there are two gamma GT mRNA populations in human lung tissue. We define these as group I (2.4 kb) and group II (approximately 1.2 kb) transcripts. In the present communication, we characterize the unique lung transcript. Sequence analysis of representative clones shows that group I transcripts are virtually identical to those previously isolated from liver and placenta but possess a unique 5' untranslated region. In marked contrast, group II transcripts appear to be human-lung-specific. Group II transcripts appear on Northern blots probed with full-length or 3'-biased gamma GT cDNA. Sequence analysis of group II clones shows them to be homologous with group I clones in the region that encodes the reading frame for the light chain; however, they possess a series of unique 5' untranslated regions, which suggests that they arise from lung-specific message processing. Additionally, approximately 50% of the isolated group II clones contain 34 nt substitutions compared with the "wild-type" gamma GT transcripts. These data indicate that human lung expresses unique gamma GT transcripts of unknown function as well as the classical form. The abundant group II transcripts may encode part of a heterodimer related to gamma GT or represent processed lung-specific pseudogenes.

A pump-pore model for transmembrane transport of hydrophilic solutes

Transmembrane transport of a hydrophilic solute is presumed to begin when hydrated ligand adheres in Velcro-like fashion to hydrated membrane surface. Asymmetric physical forces cause rolling movements of ligand over membrane surface until contact occurs with appropriate transport machinery, consisting of a pump (Pu) to which is tethered a ligand (Li)-specific perm-selective pore (Po). The Po is in the open form when the Li is attached to an external high-affinity allosteric site on it. The active form of the Pu is stabilized by attachment of the Li to high-affinity internal or low-affinity external allosteric sites. The active form of the Pu induces closure of the Po, even when ligand is bound to it; the inactive conformation of the Pu permits Po opening. Attachment of Li to either one of two binding sites on the active Pu and irreversible envelopment by it in Venus fly-trap fashion trigger transmembrane transport of Li. Multistep attachment of Li is rate-limiting in the transport process. Application of a simple equation derived from relevant kinetic considerations relating velocity of transport (V) to concentration of Li (L), V = k1(L)1/2, gives V-L curves approximating transport data obtained in a variety of biological systems. This model is congruent with the ability of cells to concentrate substances from extremely dilute solutions and with the adaptive informational value to cells of rates of transport.

Localization of a gamma-glutamyl-transferase-related gene family on chromosome 22

A gene family encompassing a minimum of four genes or pseudogenes for gamma-glutamyl transferase (GGT; EC 2.3.2.2) is present on chromosome 22q11. We have previously isolated a cDNA related to GGT but clearly not belonging to its gene family. The chromosomal location of this related gene, GGTLA1, has been determined by both isotopic and fluorescence in situ hybridization to metaphase cells and by Southern blot analysis of somatic cell hybrid DNAs. We show that GGTLA1 is part of a distinct gene family, which has at least four members (GGTLA1, GGTLA2, GGTLA3, GGTLA4). At least two loci are located on chromosome 22 within band q11 and proximal to the chronic myelogenous leukemia (CML) breakpoint in BCR (breakpoint cluster region gene). At least one other member is located more distally between the breakpoints found in Ewings sarcoma and CML. Some of the GGT and GGTLA family members are located on NotI restriction enzyme fragments of a similar size. Combined results indicate that a segment of human chromosome 22q11 has undergone large-scale amplification events relatively recently in evolution.

A panel of human chromosome 22-specific sequence tagged sites

A panel of 29 sequence tagged sites (STSs) covering the long arm of chromosome 22 has been assembled. STS primer pairs were synthesized using available chromosome 22 sequence derived from the GenBank and EMBL DNA sequence databases, as well as published cDNA and genomic sequence, or from previously published and communicated primer pairs. Each STS was optimized for the polymerase chain reaction using a chromosome 22-only hybrid and human genomic DNA. Further STS content analysis on a panel of somatic cell hybrids that incorporated two chromosome 22 translocations resulted in the mapping of the X-box binding protein (XBP), D22S156, and transcobalamin II (TCN2) genes to 22q11-q13.1. The panel of STSs was used for the rapid determination of the STS content and thus the chromosomal DNA content of a new irradiation hybrid.

Rapid isolation of cosmids from defined subregions by differential Alu-PCR hybridization on chromosome 22-specific library

A method based on the differential screening of a chromosome-specific cosmid library with amplified inter-Alu sequences obtained from a set of somatic cell hybrids has been developed to target the isolation of probes from predefined subchromosomal regions. As a model system, we have used a chromosome 22-specific cosmid library and four cell hybrids containing different parts of this chromosome. The procedure has identified cosmids that demonstrate differential hybridization signals with Alu-PCR products from these cell hybrids. We show, by in situ hybridization or individual mapping, that their hybridization pattern is indicative of their sublocalization on chromosome 22, thus resulting in a large enrichment factor for the isolation of probes from specific small chromosome subregions. Depending on the local Alu-sequence density, from 3 to 10 independent loci per megabase of genome can thus be identified.

The development and application of automated gridding for efficient screening of yeast and bacterial ordered libraries

An automated gridding procedure for the inoculation of yeast and bacterial clones in high-density arrays has been developed. A 96-pin inoculating tool compatible with the standard microtiter plate format and an eight-position tablet have been designed to fit the Biomek 1000 programmable robotic workstation (Beckman Instruments). The system is used to inoculate six copies of 80 x 120-mm filters representing a total of approximately 20,000 individual clones in approximately 3 h. High-density arrays of yeast artificial chromosome (YAC) and cosmid clones have been used for rapid large-scale hybridization screens of ordered libraries. In addition, an improved PCR library screening strategy has been developed using strips cut from the high-density arrays to prepare row and column DNA pools for PCR analysis. This strategy eliminates the final hybridization step and allows identification of a single clone by PCR in 2 days. The development of automated gridding technology will have a significant impact on the establishment of fully versatile screening of ordered library resources for genomic studies.

Regulation of mouse mammary-gland gamma-glutamyltranspeptidase mRNA during pregnancy, lactation and weaning

The level of gamma-glutamyltranspeptidase (GGT) activity and of its mRNA were determined in the mouse mammary gland during pregnancy, lactation and weaning. The GGT activity, which is very low in the virgin-mouse mammary gland (5 munits/mg of protein), increases progressively during pregnancy (3-fold), reaches its maximum at the onset of lactation (8-fold) and returns rapidly to basal level at weaning. Although no GGT-specific mRNA is detected in the virgin-mouse mammary gland, a single faint band of 2.2 kb in size is found during pregnancy. During lactation, an additional mRNA of 2.4 kb in size appears, and the level of both mRNAs is higher. This high level of mRNA persists during weaning as well. Southern-blot analysis of mouse mammary-gland DNA provides convincing evidence that there is only one gene which codes for the two mRNAs. The present study provides the first evidence for a physiological regulation of the two GGT mRNAs in the same tissue.

Mechanism of gamma-glutamyl transpeptidase release in serum during intrahepatic and extrahepatic cholestasis in the rat: a histochemical, biochemical and molecular approach

The mechanism of the elevation of serum gamma-glutamyl transpeptidase activity in cholestasis is not clear. We therefore analyzed rat gamma-glutamyl transpeptidase activities in liver, bile and serum during intrahepatic cholestasis induced by a single dose of alpha-naphthyl isothiocyanate (20 mg/100 gm body weight) and during extrahepatic cholestasis after bile duct ligation. At days 1 and 2 after alpha-naphthyl isothiocyanate ingestion, we saw a fivefold and a 60-fold increase in serum and bile gamma-glutamyl transpeptidase activities, respectively. These increases were associated with a decrease in hepatic gamma-glutamyl transpeptidase activity and of corresponding mRNA. Simultaneously, necrosis of the biliary epithelium appeared in portal tracts. From day 2 to day 14, gamma-glutamyl transpeptidase activity in bile and serum progressively returned to basal levels; in the liver, cholangiolar proliferation was mild and was associated with moderate elevation of the gamma-glutamyl transpeptidase activity and of its corresponding mRNA. In extrahepatic cholestasis, a 10-fold increase in serum gamma-glutamyl transpeptidase activity was detected between day 0 and day 14. This increase was associated with major cholangiolar proliferation and with a progressive rise in hepatic gamma-glutamyl transpeptidase activity and in specific mRNA; in bile, gamma-glutamyl transpeptidase activity was slightly elevated. In these two models of cholestasis, histochemically detected gamma-glutamyl transpeptidase activity was largely predominant in biliary cells. We found no significant induction of gamma-glutamyl transpeptidase activity in hepatocytes. These results suggest that in these two models of cholestasis, the increase in serum gamma-glutamyl transpeptidase activity is of biliary cell origin and does not originate from hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Different gamma-glutamyl transpeptidase mRNAs are expressed in human liver and kidney

In human, the two subunits of gamma-glutamyl transpeptidase (GGT) arise from a common precursor encoded by a multigene family. Until now, a single specific coding sequence for this precursor (type I) has been identified in human placenta and liver. In the present study, we have isolated from a human kidney cDNA library, a GGT specific clone (0.8 Kb). The sequence of which (type II) i) covers the carboxy terminal part of the GGT precursor, ii) exhibits 22 point mutations and a 30 bp deletion as compared to the type I GGT sequence. The sequencing of a human genomic clone reveals that this type II GGT mRNA is encoded by a different gene than the type I GGT mRNA. Both type I and type II GGT mRNAs are expressed in human liver, while almost exclusively type II GGT mRNA is detected in human kidney.

Cloning and nucleotide sequence of human gamma-glutamyl transpeptidase

We have identified the gene for human gamma-glutamyl transpeptidase [GGT; glutamine:D-glutamyl-peptide 5-glutamyltransferase (also called gamma-glutamyltransferase), EC 2.3.2.2] in a BCR gene-related region located in band q11----qter of chromosome 22. Two cDNAs complementary to the GGT mRNA have been isolated from a human placental library constructed in phage lambda gt11. The largest cDNA has a size of 2535 base pairs (bp) and an open reading frame of 1707 nucleotides encoding 569 amino acids. By using a probe corresponding to this cDNA, a mRNA of approximately 2.4 kilobases was detected by RNA blot-hybridization analysis in mouse kidney RNA. The GGT precursor encoded by the coding sequence would have an estimated Mr of 61,400. We compared our nucleotide and deduced amino acid sequences with the published results of rat kidney cDNAs. The human and rat amino acid sequences are similar; however, a considerable discrepancy in nucleotide sequence was found within a 180-bp fragment of the heavy chain, resulting in a completely different amino acid sequence for this region. In addition, the 5' untranslated sequence of the human cDNA (669 bp) is substantially larger than that determined in the rat cDNA (227 bp). Our results may be valuable for further studies on the protein structure of human GGT as well as studies on the regulation of the enzyme.

The human lactase-phlorizin hydrolase gene is located on chromosome 2

The lactase-phlorizin hydrolase gene was assigned to chromosome 2 by analysis of Southern blots of DNA from a panel of human-rodent cell hybrids containing characteristic sets of human chromosomes The hybridization probe used was a recently isolated cDNA clone of the human lactase-phlorizin hydrolase gene.

Assignment of the human aminopeptidase N (peptidase E) gene to chromosome 15q13-qter

The gene for aminopeptidase N (EC 3.4.11.2) has been located on the human chromosome 15q13-qter using HindIII-cleaved DNA from a panel of hybrids between rodent and human cells. The Southern blots were probed by the 5'-EcoRI fragment of the recently cloned human aminopeptidase N cDNA.

Duplication of the bcr and gamma-glutamyl transpeptidase genes

The Philadelphia (Ph') translocation involves rearrangement of the bcr gene located on chromosome 22. Hybridization experiments revealed the presence of multiple bcr gene-related loci within the human genome. Two of these were molecularly cloned and characterized. Both loci contain exons and introns corresponding to the 3' region of the bcr gene. Restriction enzyme and DNA sequence analysis indicate a very high degree of conservation between bcr and the two related genomic sequences. Both bcr-related loci are located on chromosome 22, one centromeric, the other telomeric, of the bcr gene. Within the two bcr related genomic sequences, fragments or the complete coding sequences of an unrelated gene were found to be present. This gene was identified; it encodes gamma-glutamyl transferase, an enzyme involved in the glutathione metabolism.