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Characterization of human mucin MUC17. Complete coding sequence and organization.

With increasing interest on mucins as diagnostic and therapeutic targets in cancers and other diseases, it is becoming imperative to characterize novel mucins and investigate their biological significance. Here, we present the completed coding sequence and genomic organization of the previously published partial cDNA sequence of MUC17. Rapid amplification of cDNA ends with PCR, sequences from the Human Genome databases, and in vitro transcription/translational assays were used for these analyses. The MUC17 gene is located within a 39-kb DNA fragment between MUC12 and SERPINE1 on chromosome 7 in the region q22.1. The full-length coding sequence of MUC17 transcribes a 14.2-kb mRNA encompassing 13 exons. Alternate splicing generates two variants coding for a membrane-anchored and a secreted form. The canonical variable number of tandem repeats polymorphism of the central tandem repeat domain of the MUC genes is not significantly detected in the MUC17 gene. In addition, we show the overexpression of MUC17 by Western blot and immunohistochemical analyses in pancreatic tumor cell lines and tumor tissues compared with the normal pancreas. The expression of MUC17 is regulated by a 1,146-bp fragment upstream of MUC17 that contains VDR/RXR, GATA, NFkappaB, and Cdx-2 response elements.

5' Untranslated Regions↗

Synergistic computational and experimental proteomics approaches for more accurate detection of active serine hydrolases in yeast.

An analysis of the structurally and catalytically diverse serine hydrolase protein family in the Saccharomyces cerevisiae proteome was undertaken using two independent but complementary, large-scale approaches. The first approach is based on computational analysis of serine hydrolase active site structures; the second utilizes the chemical reactivity of the serine hydrolase active site in complex mixtures. These proteomics approaches share the ability to fractionate the complex proteome into functional subsets. Each method identified a significant number of sequences, but 15 proteins were identified by both methods. Eight of these were unannotated in the Saccharomyces Genome Database at the time of this study and are thus novel serine hydrolase identifications. Three of the previously uncharacterized proteins are members of a eukaryotic serine hydrolase family, designated as Fsh (family of serine hydrolase), identified here for the first time. OVCA2, a potential human tumor suppressor, and DYR-SCHPO, a dihydrofolate reductase from Schizosaccharomyces pombe, are members of this family. Comparing the combined results to results of other proteomic methods showed that only four of the 15 proteins were identified in a recent large-scale, "shotgun" proteomic analysis and eight were identified using a related, but similar, approach (neither identifies function). Only 10 of the 15 were annotated using alternate motif-based computational tools. The results demonstrate the precision derived from combining complementary, function-based approaches to extract biological information from complex proteomes. The chemical proteomics technology indicates that a functional protein is being expressed in the cell, while the computational proteomics technology adds details about the specific type of function and residue that is likely being labeled. The combination of synergistic methods facilitates analysis, enriches true positive results, and increases confidence in novel identifications. This work also highlights the risks inherent in annotation transfer and the use of scoring functions for determination of correct annotations.

Amino Acid Sequence↗

How are genes measured? Examples from studies on iron metabolism in pregnancy.

As the 21st century moves forward, it is becoming more and more apparent that the genetic makeup of any individual strongly influences the way they metabolise nutrients. It is very important, therefore, to understand the techniques and technologies used to assess the contribution genes make to the physiology of an individual. Clearly, it is not possible to provide a comprehensive overview, but in the present review an attempt will be made to show, using examples from the authors' research, how these methods have contributed to this understanding. Studies are being undertaken into Fe transport across the placenta, from the mother to the fetus, and the consequences of maternal anaemia on pregnancy outcome. Levels of gene transcript and protein have been measured using Northern and Western blotting respectively. During the course of this work a new protein has been identified using the available human genome database. Following this 'in silico' or 'cyber biology', techniques such as real-time RT-PCR and RNA interference have been used to examine expression of this gene and its protein. The methods used, briefly how they work and some of their limitations will be explained. The objective of the present review is primarily to give a better perception of how molecular biology can be used in research and to help gain a clearer understanding of some of the techniques used.

Anemia, Iron-Deficiency↗

Isolation and sequencing of a putative promoter region of the murine G protein beta 1 subunit (GNB1) gene.

The expression of the heterotrimeric GTP-binding protein beta 1 subunit gene (GNB1) is regulated by psychostimulants such as cocaine and amphetamines. Since the up-regulation appears to be one of the candidate processes of sensitization, it is necessary to elucidate the cellular and molecular mechanism of the GNB1 gene regulation for a better understanding the establishment of sensitization. In the present study, we describe the isolation and nucleotide sequence analysis of the GNB1 gene promoter region. We have isolated approximately 10 kb of the 5'-flanking region of the mouse of GNB1 gene and found potential elements involved in putative transcriptional control of the GNB1, such as AP1, AP2, Sp1, cyclic AMP response element, and nuclear factor kappa B recognition sites, within the sequences 0.3 kb upstream from the putative transcription start site. This region was highly rich in G + C content, but lacked TATA or CATT boxes. Comparing the nucleotide sequence of the cDNA clone with the human genome databases using the BLAST program a region containing putative exon 1 and promoter of the human GNB1 gene in chromosome 1 was found. The cloning and sequence analysis of an extensive portion of the 5'-flanking regulatory region of the GNB1 gene provides new insights into the factors involved in the regulation by psychostimulants of GNB1 expression.

5' Flanking Region↗

Identification of a novel splice variant: human SGT1B (SUGT1B).

We identified a novel splice variant of human SGT1 (SUGT1), a suppressor of the G2 allele of SKP1, by analysis of 8 human EST clones whose open reading frame encoded 365 amino acids. We termed this variant SGT1B (SUGT1B) and the original SGT1A (SUGT1A). The putative SGT1B and SGT1A proteins are 91% identical, and both contain a tetratricopeptide repeat (TPR) domain, two variable regions, a CS domain, and a SGS domain. The NCBI human genome database showed that SGT1B and SGT1A are located on chromosome band 13q14.13. SGT1B contains an additional 33 amino acids encoded by a region between exons 5 and 6 of SGT1A and lacks Ser110 of SGT1A. Immunoblotting using antibodies to N-terminal (amino acids 1-157) and C-terminal (amino acids 182-333) regions of SGT1A detected 2 bands whose sizes corresponded to those predicted for SGT1A and SGT1B. Overexpression experiments confirmed this finding. Additional immunoblot analysis demonstrated that both are highly expressed in human brain, liver, lung, and testis.

Alternative Splicing↗

Molecular cloning and characterization of SGT1.2, a novel splice variant of Homo sapiens SGT1.

SGT1.2, a novel splice variant of Homo sapiens SGT1 was isolated from a human fetal brain cDNA library. This cDNA is 1404 bp and contains an open reading frame from 68 to 1165 encoding a putative protein of 365 amino acids (SGT1.2) that share 90% identities to Homo sapiens SGT1, suppressor of G2 allele of SKP1 at protein level. RPS-BLAST searching revealed that SGT1.2 have a TPR domain, a p23 domain, a SGS domain and a CS domain. According to the search of the human genome database, SGT1.2 was mapped to human chromosome 13q14.13. Reversed transcription-polymerase chain reaction analysis indicated that it widely expressed in human adult tissues.

Alternative Splicing↗

Cloning and characterization of a novel transcript variant of IQGAP2 in human testis.

Using cDNA microarray hybridization from a human testicular cDNA library, one gene exhibiting 6.4-fold difference at expression level between adult and embryo human testes was cloned and named tsIQGAP2 (testis specific IQ motif containing GTPase-activating protein 2). The full cDNA length of tsIQGAP2 is 3388 bp and contains a 3215 bp open reading frame, encoding a 122.85 kDa protein of 1071 amino acids. Sequence analysis showed that tsIQGAP2 harbors all the domains (one WW domain, three IQ motifs, and one RasGAP homology domain) in HsIQGAP2 (IQ motif containing GTPase-activating protein 2) except for the N-terminal calponin homology domain. Blasting human genome database localized tsIQGAP2 to human chromosome 5q13-14 and further investigation showed that it is a novel transcript variant of HsIQGAP2. The tissue distribution of tsIQGAP2 showed that it is a testis specific gene. The above results suggest the potential role of tsIQGAP2 during spermatogenesis and the mechanism by which tsIQGAP2 regulating spermatogenesis also has been proposed.

Alternative Splicing↗

Isolation, tissue distribution and prokaryotic expression of a novel human X-linked gene LHFPL1.

We report here the cloning and characterization of a novel human lipoma HMGIC fusion partner-like 1 (LHFPL1) gene, isolated from human brain cDNA library, and mapped to Xq23 by browsing the UCSC genomic database. LHFPL1 contains an ORF with length of 660bp, encoding a protein with a signal peptide sequence and three transmembrane regions, and its predicted molecular weight is 23.7kDa which coincides with the result of prokaryotic expression. LHFPL1 protein is postulated to be localized at endoplasmic reticulum. RT-PCR amplification in seventen human tissues revealed that LHFPL1 is expressed widely in all tissues, especially highly in lung, thymus, skeleton muscle, colon and ovary. In addition, it was demonstrated that LHFPL1 is also transcribed in six liver tumor cell lines.

Amino Acid Sequence↗

Cloning and characterization of the mouse ortholog of mi-er1.

Mi-er1 is a fibroblast growth factor immediate-early gene whose expression is differentially regulated in breast tumours. MI-ER1 functions as a transcriptional repressor of a number of genes, including Sp1 target genes. The Xenopus and human orthologs have been described and here we report the characterization of the mouse gene and its products. Mouse mi-er1 is a single copy gene located on chromosome 4. It has the same intron-exon structure as the human gene with the exception of exon 3A, in which an upstream 3' splice acceptor is utilized. As described in humans, multiple transcripts are produced in the mouse, and we have isolated the mouse orthologs of the human N1-beta, N2-beta and N3-beta, all of, which differ in their N-terminal sequence. Furthermore, we have isolated a novel isoform, N4-beta, containing sequence from an additional exon located between exon 4 and exon 5 that produces an fourth alternate N-terminus. The human mi-er1 transcripts also include isoforms encoding two alternate C-termini, alpha and beta. Like Xenopus, only isoforms containing the beta C-terminus have been detected in the mouse. Expression analysis, using a panel of mouse tissues and embryos, revealed that the N1-beta and N3-beta are ubiquitously expressed while N4-beta is only expressed in testis. N2-beta is expressed in most tissues but was not detected in heart, brain, eye or skeletal muscle. Sequence comparison revealed 95% identity between mouse and human MI-ER1 isoforms and 72% identity between mouse and Xenopus. The most conserved region in the MI-ER1 protein is the SANT domain, which is identical in all three species. Further analysis of the SANT domain using sequences retrieved from the genome databases for rat, cow, chicken, zebrafish, trout and Xenopustropicalis revealed that this domain is highly conserved, with 88% identity among the 9 species. Moreover, an additional 10 residues C-terminal to the published end of this domain are 100% conserved, suggesting that in MI-ER1, the functional domain includes this extended sequence.

Amino Acid Sequence↗

Cloning and characterization of the CDZFP gene which encodes a putative zinc finger protein.

We report here the cloning and characterization of a novel human cytoplasm-distribution zinc finger protein (CDZFP) gene, isolated from human ovary cDNA library, and mapped to 4p12 by searching the UCSC genomic database. The CDZFP cDNA is 1793 base pairs in length and contains an open reading frame (ORF) encoding 236 amino acids. The CDZFP gene consists of 7 exons and encodes a putative zinc finger protein with a transmembrane region and two zinc finger motifs. Subcellular localization demonstrated that CDZFP protein was located in the cytoplasm when overexpressed in Hela cells and northern blot analysis revealed that CDZFP was ubiquitously expressed in 16 human tissues.

Amino Acid Sequence↗

Plasmodium falciparum carbonic anhydrase is a possible target for malaria chemotherapy.

Plasmodiumfalciparum is responsible for the majority of life-threatening cases of human malaria. The global emergence of drug-resistant malarial parasites necessitates identification and characterization of novel drug targets. Carbonic anhydrase (CA) is present at high levels in human red cells and in P. falciparum. Existence of at least three isozymes of the alpha < class was demonstrated in P. falciparum and a rodent malarial parasite Plasmodium berghei. The major isozyme CA1 was purified and partially characterized from P. falciparum (PfCA1). A search of the malarial genome database yielded an open reading frame similar to the alpha-CAs from various organisms, including human. The primary amino acid sequence of the PfCA1 has 60% identity with a rodent parasite Plasmodium yoelii enzyme (PyCA). The single open reading frames encoded 235 and 252 amino acid proteins for PfCA1 and PyCA, respectively. The highly conserved active site residues were also found among organisms having alpha-CAs. The PfCA1 gene was cloned, sequenced and expressed in Escherichia coli. The purified recombinant PfCA1 enzyme was catalytically active. It was sensitive to acetazolamide and sulfanilamide inhibition. Kinetic properties of the recombinant PfCA1 revealed the authenticity to the wild type enzyme purified from P. falciparum in vitro culture. Furthermore, the PfCA1 inhibitors acetazolamide and sulfanilamide showed good antimalarial effect on the in vitro growth of P. falciparum. Our molecular tools developed for the recombinant enzyme expression will be useful for developing potential antimalarials directed at P. falciparum carbonic anhydrase.

Acetazolamide↗

Branched mitochondrial electron transport in the Animalia: presence of alternative oxidase in several animal phyla.

The mitochondrion of most eukaryotes has multiple electron transport components that increase the points of entry and/or exit of electrons, thus giving a branched nature to the respiratory chain. In plants and many other organisms, a prominent example is alternative oxidase, a non-energy conserving branch in the respiratory chain and an additional terminal oxidase for the exit of electrons. Our genome database searches have now revealed the presence of alternative oxidase in four animal species from three different phyla (Mollusca, Nematoda and Chordata), consistent with frequent reports of cyanide-resistant respiration in the Animalia. In Ciona intestinalis and Crassostrea gigas, alternative oxidase is expressed in several different tissues. Phylogenetic analysis is consistent with the animal proteins having originated by vertical inheritance. We hypothesize that alternative oxidase is likely widespread in the Animalia and discuss some of the potential role(s) for such a branched respiratory chain.

Amino Acid Sequence↗

Evolutionary analysis of fructose 2,6-bisphosphate metabolism.

Fructose 2,6-bisphosphate is a potent metabolic regulator in eukaryotic organisms; it affects the activity of key enzymes of the glycolytic and gluconeogenic pathways. The enzymes responsible for its synthesis and hydrolysis, 6-phosphofructo-2-kinase (PFK-2) and fructose-2,6-bisphosphatase (FBPase-2) are present in representatives of all major eukaryotic taxa. Results from a bioinformatics analysis of genome databases suggest that very early in evolution, in a common ancestor of all extant eukaryotes, distinct genes encoding PFK-2 and FBPase-2, or related enzymes with broader substrate specificity, fused resulting in a bifunctional enzyme both domains of which had, or later acquired, specificity for fructose 2,6-bisphosphate. Subsequently, in different phylogenetic lineages duplications of the gene of the bifunctional enzyme occurred, allowing the development of distinct isoenzymes for expression in different tissues, at specific developmental stages or under different nutritional conditions. Independently in different lineages of many unicellular eukaryotes one of the domains of the different PFK-2/FBPase-2 isoforms has undergone substitutions of critical catalytic residues, or deletions rendering some enzymes monofunctional. In a considerable number of other unicellular eukaryotes, mainly parasitic organisms, the enzyme seems to have been lost altogether. Besides the catalytic core, the PFK-2/FBPase-2 has often N- and C-terminal extensions which show little sequence conservation. The N-terminal extension in particular can vary considerably in length, and seems to have acquired motifs which, in a lineage-specific manner, may be responsible for regulation of catalytic activities, by phosphorylation or ligand binding, or for mediating protein-protein interactions.

Animals↗

P450 oxidoreductase deficiency: a new disorder of steroidogenesis affecting all microsomal P450 enzymes.

Combined partial deficiency of 17alpha-hydroxylase and 21-hydroxylase activities was first described in 1985; however the genes for P450c17 and P450c21 in these patients lack mutations. In 1986 we postulated that this disorder might be due to mutations in P450 oxidoreductase (POR), the flavoprotein that donates electron to these and all other microsomal P450 enzymes, but this hypothesis was not tested until the POR gene sequence became available through the genome database. We found five POR missense mutations in our first four patients. In vitro assays of the activities of these mutations showed that the standard assay of POR activity, reduction of cytochrome c, correlated poorly with the patients' phenotypes, but that assays of POR-supported 17alpha-hydroxylase and 17,20 lyase activities correlated well. POR deficiency is a new disorder of adrenal and gonadal steroidogenesis that affects all microsomal cytochrome P450 enzymes, hence may have important implications for genetic differences in drug metabolism.

Abnormalities, Multiple↗

A small conserved domain in the yeast Spa2p is necessary and sufficient for its polarized localization.

SPA2 encodes a yeast protein that is one of the first proteins to localize to sites of polarized growth, such as the shmoo tip and the incipient bud. The dynamics and requirements for Spa2p localization in living cells are examined using Spa2p green fluorescent protein fusions. Spa2p localizes to one edge of unbudded cells and subsequently is observable in the bud tip. Finally, during cytokinesis Spa2p is present as a ring at the mother-daughter bud neck. The bud emergence mutants bem1 and bem2 and mutants defective in the septins do not affect Spa2p localization to the bud tip. Strikingly, a small domain of Spa2p comprised of 150 amino acids is necessary and sufficient for localization to sites of polarized growth. This localization domain and the amino terminus of Spa2p are essential for its function in mating. Searching the yeast genome database revealed a previously uncharacterized protein which we name, Sph1p (a2p omolog), with significant homology to the localization domain and amino terminus of Spa2p. This protein also localizes to sites of polarized growth in budding and mating cells. SPH1, which is similar to SPA2, is required for bipolar budding and plays a role in shmoo formation. Overexpression of either Spa2p or Sph1p can block the localization of either protein fused to green fluorescent protein, suggesting that both Spa2p and Sph1p bind to and are localized by the same component. The identification of a 150-amino acid domain necessary and sufficient for localization of Spa2p to sites of polarized growth and the existence of this domain in another yeast protein Sph1p suggest that the early localization of these proteins may be mediated by a receptor that recognizes this small domain.

Amino Acid Sequence↗

Identification and characterization of novel superantigens from Streptococcus pyogenes.

Three novel streptococcal superantigen genes (spe-g, spe-h, and spe-j) were identified from the Streptococcus pyogenes M1 genomic database at the University of Oklahoma. A fourth novel gene (smez-2) was isolated from the S. pyogenes strain 2035, based on sequence homology to the streptococcal mitogenic exotoxin z (smez) gene. SMEZ-2, SPE-G, and SPE-J are most closely related to SMEZ and streptococcal pyrogenic exotoxin (SPE)-C, whereas SPE-H is most similar to the staphylococcal toxins than to any other streptococcal toxin. Recombinant (r)SMEZ, rSMEZ-2, rSPE-G, and rSPE-H were mitogenic for human peripheral blood lymphocytes with half-maximal responses between 0.02 and 50 pg/ml (rSMEZ-2 and rSPE-H, respectively). SMEZ-2 is the most potent superantigen (SAg) discovered thus far. All toxins, except rSPE-G, were active on murine T cells, but with reduced potency. Binding to a human B-lymphoblastoid line was shown to be zinc dependent with high binding affinity of 15-65 nM. Evidence from modeled protein structures and competitive binding experiments suggest that high affinity binding of each toxin is to the major histocompatibility complex class II beta chain. Competition for binding between toxins was varied and revealed overlapping but discrete binding to subsets of class II molecules in the hierarchical order (SMEZ, SPE-C) > SMEZ-2 > SPE-H > SPE-G. The most common targets for the novel SAgs were human Vbeta2.1- and Vbeta4-expressing T cells. This might reflect a specific role for this subset of Vbetas in the immune defense of gram-positive bacteria.

Amino Acid Sequence↗

Dominant hereditary inclusion-body myopathy gene (IBM3) maps to chromosome region 17p13.1.

We recently described an autosomal dominant inclusion-body myopathy characterized by congenital joint contractures, external ophthalmoplegia, and predominantly proximal muscle weakness. A whole-genome scan, performed with 161 polymorphic markers and with DNA from 40 members of one family, indicated strong linkage for markers on chromosome 17p. After analyses with additional markers in the region and with DNA from eight additional family members, a maximum LOD score (Zmax) was detected for marker D17S1303 (Zmax=7.38; recombination fraction (theta)=0). Haplotype analyses showed that the locus (Genome Database locus name: IBM3) is flanked distally by marker D17S945 and proximally by marker D17S969. The positions of cytogenetically localized flanking markers suggest that the location of the IBM3 gene is in chromosome region 17p13.1. Radiation hybrid mapping showed that IBM3 is located in a 2-Mb chromosomal region and that the myosin heavy-chain (MHC) gene cluster, consisting of at least six genes, co-localizes to the same region. This localization raises the possibility that one of the MHC genes clustered in this region may be involved in this disorder.

Chromosome Mapping↗

Genetic inheritance of gene expression in human cell lines.

Combining genetic inheritance information, for both molecular profiles and complex traits, is a promising strategy not only for detecting quantitative trait loci (QTLs) for complex traits but for understanding which genes, pathways, and biological processes are also under the influence of a given QTL. As a primary step in determining the feasibility of such an approach in humans, we present the largest survey to date, to our knowledge, of the heritability of gene-expression traits in segregating human populations. In particular, we measured expression for 23,499 genes in lymphoblastoid cell lines for members of 15 Centre d'Etude du Polymorphisme Humain (CEPH) families. Of the total set of genes, 2,340 were found to be expressed, of which 31% had significant heritability when a false-discovery rate of 0.05 was used. QTLs were detected for 33 genes on the basis of at least one P value <.000005. Of these, 13 genes possessed a QTL within 5 Mb of their physical location. Hierarchical clustering was performed on the basis of both Pearson correlation of gene expression and genetic correlation. Both reflected biologically relevant activity taking place in the lymphoblastoid cell lines, with greater coherency represented in Kyoto Encyclopedia of Genes and Genomes database (KEGG) pathways than in Gene Ontology database pathways. However, more pathway coherence was observed in KEGG pathways when clustering was based on genetic correlation than when clustering was based on Pearson correlation. As more expression data in segregating populations are generated, viewing clusters or networks based on genetic correlation measures and shared QTLs will offer potentially novel insights into the relationship among genes that may underlie complex traits.

Cell Line↗