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PubMed1988

Structure and chromosomal localization of the functional intronless human JUN protooncogene.

The JUN protooncogene encodes a protein that is functionally and biochemically identical to the transcription factor AP-1 (activator protein 1). To understand the structure and regulation of this important gene, a genomic clone of human JUN was isolated and its primary structure and transcription pattern were determined. Most surprisingly, the sequence of the genomic clone was found to be contiguous with the sequence of the JUN cDNA, suggesting that it lacks introns. RNase protection experiments confirm that JUN is an intronless gene that yields several transcripts due to 5' and 3' heterogeneities. Transfection experiments show that the cloned gene is functional, as it encodes a trans-acting factor that stimulates transcription of AP-1-dependent reporter gene. In situ hybridization was used to map JUN to chromosomal region 1p31-32. Interestingly, this region is frequently deleted in neuroblastomas, suggesting that elimination of AP-1 may play an important role in the pathogenesis of this disease.

Amino Acid Sequence↗
PubMed2005

Bacterial chromosome segregation: structure and DNA binding of the Soj dimer--a conserved biological switch.

Soj and Spo0J of the Gram-negative hyperthermophile Thermus thermophilus belong to the conserved ParAB family of bacterial proteins implicated in plasmid and chromosome partitioning. Spo0J binds to DNA near the replication origin and localises at the poles following initiation of replication. Soj oscillates in the nucleoid region in an ATP- and Spo0J-dependent fashion. Here, we show that Soj undergoes ATP-dependent dimerisation in solution and forms nucleoprotein filaments with DNA. Crystal structures of Soj in three nucleotide states demonstrate that the empty and ADP-bound states are monomeric, while a hydrolysis-deficient mutant, D44A, is capable of forming a nucleotide 'sandwich' dimer. Soj ATPase activity is stimulated by Spo0J or the N-terminal 20 amino-acid peptide of Spo0J. Our analysis shows that dimerisation and activation involving a peptide containing a Lys/Arg is conserved for Soj, ParA and MinD and their modulators Spo0J, ParB and MinE, respectively. By homology to the nitrogenase iron protein and the GTPases Ffh/FtsY, we suggest that Soj dimerisation and regulation represent a conserved biological switch.

Adenosine Triphosphate↗
PubMed2002

Male mouse recombination maps for each autosome identified by chromosome painting.

Linkage maps constructed from genetic analysis of gene order and crossover frequency provide few clues to the basis of genomewide distribution of meiotic recombination, such as chromosome structure, that influences meiotic recombination. To bridge this gap, we have generated the first cytological recombination map that identifies individual autosomes in the male mouse. We prepared meiotic chromosome (synaptonemal complex [SC]) spreads from 110 mouse spermatocytes, identified each autosome by multicolor fluorescence in situ hybridization of chromosome-specific DNA libraries, and mapped >2,000 sites of recombination along individual autosomes, using immunolocalization of MLH1, a mismatch repair protein that marks crossover sites. We show that SC length is strongly correlated with crossover frequency and distribution. Although the length of most SCs corresponds to that predicted from their mitotic chromosome length rank, several SCs are longer or shorter than expected, with corresponding increases and decreases in MLH1 frequency. Although all bivalents share certain general recombination features, such as few crossovers near the centromeres and a high rate of distal recombination, individual bivalents have unique patterns of crossover distribution along their length. In addition to SC length, other, as-yet-unidentified, factors influence crossover distribution leading to hot regions on individual chromosomes, with recombination frequencies as much as six times higher than average, as well as cold spots with no recombination. By reprobing the SC spreads with genetically mapped BACs, we demonstrate a robust strategy for integrating genetic linkage and physical contig maps with mitotic and meiotic chromosome structure.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Structure and chromosomal location of mouse and human CD52 genes.

Human CD52 (CAMPATH-1 antigen) is an abundant surface molecule on lymphocytes and a favoured target for lymphoma therapy and immunosuppression. It comprises a small glycosylphosphatidylinositol (GPI) anchored peptide to which a large carbohydrate moiety is attached. Structurally similar proteins include the proposed mouse homologue, B7 antigen (B7-Ag; not to be confused with the CD28 ligand), and human and mouse CD24. Sequence similarities between CD52 and B7-Ag precursors are concentrated over the signal peptides and the sequences cleaved during GPI attachment. While the short mature peptides are not apparently homologous, the N-linked glycosylation site is retained in both. We describe similarities in exon-intron organisation, syntenic chromosome positions (human CD52, 1p36; mouse B7-Ag, chromosome 4, between Dsil and D4Nds16) and sequence homology in the promoter regions which strongly suggests that B7-Ag is the mouse homologue of CD52. The structure of these genes is also similar to that of mouse CD24, suggesting a common ancestor. Promoter activities and transcription start sites were also analysed. These results suggest that human CD52 and mouse B7-Ag gene expressions are controlled by TATA-less promoters.

Amino Acid Sequence↗
PubMed2003

The mitotic chromosome is an assembly of rigid elastic axes organized by structural maintenance of chromosomes (SMC) proteins and surrounded by a soft chromatin envelope.

The structure of mitotic chromosomes is still poorly understood. Here we describe the use of a novel approach based on elasticity measurements of a single chromosome for studying the organization of these objects. The data reveal that mitotic chromosomes exhibit a non-homogenous structure consisting of rigid elastic axes surrounded by a soft chromatin envelope. The chemical continuity of DNA, but not RNA, was required for the maintenance of these axes. The axes show a modular structure, and the structural maintenance of chromosomes (SMC) proteins participate in their organization. Topoisomerase II was not involved in either the organization of the axes or the maintenance of the mitotic chromosomes. A model for the assembly and the structure of the mitotic chromosome is proposed. According this model, the chromosome axes are dynamic structures that assemble at the onset and disassemble the end of mitosis, respectively. The SMC proteins, in addition to maintaining axis elasticity, are essential for the determination of the rod-like chromosome shape. The extreme compaction of mitotic chromosomes is determined mainly by the high amount of bivalent ions bound to DNA at mitosis.

Animals↗
PubMed1981

[Chromosome abnormalities, tumours and developmental disorders (author's transl)].

Clonal chromosome disorders occurring or acquired at any postnatal age are often closely related with the origin of tumours. In man the Ph1-chromosome (9; 22) anomaly in CML or the 8; 14 translocation in the African malignant Burkitt Non-Hodgkin lymphoma are, among other cases, prominent examples. On the other hand, constitutive, inherited or novel chromosome anomalies conveyed from the zygote to all tissues of the organism may cause a higher risk for the origin of tumours. Rarely, inheritable minor structural chromosome mutations are known to determine the occurrence of dysontogenetic tumours, as e.g., nephroblastoma, but it is assumed that more such cases will become elucidated in the future. As a special phenomenon, true hydatiform mole is a tumour of the placental tissue due to a disorder of intragenome regulation. Constitutive or numerical structural chromosome anomalies of man are a frequent cause of early or late abortion or of abnormal development and malformation. Despite the predominating principle of selective fetal elimination, a few anomalies such as Down's syndrome, may escape to longer survival due to the relatively mild effects of chromosome 21 triplication. Trisomies which represent in man the most frequent type of chromosome disorders, can be induced, and systematically studied in an experimental model of the mouse. This allows the elaboration of the developmental profiles of all trisomies (and monosomies) of the mouse. Also, the above mentioned principle of selective elimination of abnormal implants can be analysed experimentally. Although the developmental span of a trisomic zygote is limited, there is evidence that cells and tissues isolated from the chromosomally abnormal organism can survive much longer. Thus, haemopoietic stem cells, at least in Ts 12 and 19 of the mouse, can be rescued from trisomic fetuses by transferring them to lethally irradiated adult mice, whose blood forming organs may eventually become permanently repopulated by the trisomic cell lineage. This type of experiments is suited for closer analyses of potential functions vs. defects of chromosomally abnormal cellular systems, e.g., with regard to growth and development.

Animals↗
PubMed1985

The human Thy-1 gene: structure and chromosomal location.

The human Thy-1 gene has been isolated and sequenced and compared to the rat and mouse Thy-1 genes. All three genes are organized in the same way: one exon encoding the majority of the signal peptide, another encoding the transmembrane segment, and a third encoding the remainder of the protein. One major structural difference between the human and rodent Thy-1 glycoproteins is that the former contains two instead of three glycosylation sites. RNA blot analysis of a human T-cell line expressing the T3 complex showed an absence of Thy-1 mRNA, excluding the possibility that Thy-1 represents one of the component chains of T3. The structural gene for human Thy-1 was localized to the long arm of chromosome 11 by nucleic acid hybridization to genomic DNA isolated from somatic cell hybrids.

Amino Acid Sequence↗
PubMed1996

Sequence, genomic structure, and chromosomal assignment of human DOC-2.

DOC-2 is a human gene originally identified as a 767-bp cDNA fragment isolated from normal ovarian epithelial cells by differential display against ovarian carcinoma cells. We have now determined the complete cDNA sequence of the 3.2-kb DOC-2 transcript and localized the gene to chromosome 5. A 12.5-kb genomic fragment at the 5'-end of DOC-2 has also been sequenced, revealing the intron-exon structure of the first eight exons (788 bases) of the DOC-2 gene. Translation of the DOC-2 cDNA predicts a hydrophobic protein of 770 amino acid residues with a molecular weight of 82.5 kDa. Comparison of the DNA and amino acid sequences of DOC-2 to publicly accessible sequence databases revealed 83% identify to p96, a murine protein of similar size, thought to be a mitogen-responsive phosphoprotein. In addition, about 45% identity was observed between the first 140 N-terminal residues of DOC-2 and the Caenorhabditas elegans M110.5 and Drosophila melanogaster Dab genes.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Structures and chromosome locations of the human MEF2A gene and a pseudogene MEF2AP.

The MEF2 family of transcription factors control the expression of muscle-specific and mitogen-induced genes. Here we describe the isolation and structure of the human MEF2A gene. The protein coding region of MEF2A is divided by 10 introns. The 3' untranslated region (UTR) is 3.7 kb in length, and it contains a region that is highly homologous with a portion of the 3' UTR of Xenopus MEF2A. A partially processed pseudogene (MEF2AP) corresponding to MEF2A was also isolated and characterized. Human MEF2A was mapped by fluorescence in situ hybridization to chromosome 15q26, and MEF2AP was mapped to chromosome 1q24 --> q25.

Animals↗
PubMed2001

Evolution of transglutaminase genes: identification of a transglutaminase gene cluster on human chromosome 15q15. Structure of the gene encoding transglutaminase X and a novel gene family member, transglutaminase Z.

We isolated and characterized the gene encoding human transglutaminase (TG)(X) (TGM5) and mapped it to the 15q15.2 region of chromosome 15 by fluorescence in situ hybridization. The gene consists of 13 exons separated by 12 introns and spans about 35 kilobases. Further sequence analysis and mapping showed that this locus contained three transglutaminase genes arranged in tandem: EPB42 (band 4.2 protein), TGM5, and a novel gene (TGM7). A full-length cDNA for the novel transglutaminase (TG(Z)) was obtained by anchored polymerase chain reaction. The deduced amino acid sequence encoded a protein with 710 amino acids and a molecular mass of 80 kDa. Northern blotting showed that the three genes are differentially expressed in human tissues. Band 4.2 protein expression was associated with hematopoiesis, whereas TG(X) and TG(Z) showed widespread expression in different tissues. Interestingly, the chromosomal segment containing the human TGM5, TGM7, and EPB42 genes and the segment containing the genes encoding TG(C),TG(E), and another novel gene (TGM6) on chromosome 20q11 are in mouse all found on distal chromosome 2 as determined by radiation hybrid mapping. This finding suggests that in evolution these six genes arose from local duplication of a single gene and subsequent redistribution to two distinct chromosomes in the human genome.

5' Untranslated Regions↗
PubMed1999

Gene structure and chromosome mapping of the human small-conductance calcium-activated potassium channel SK1 gene (KCNN1).

Small-conductance, calcium-activated potassium channels contribute to the afterhyperpolarization in central neurons and other cell types. Because these channels regulate neuronal excitability, defects in their genes could cause excitability disorders. The human cDNA encoding one such channel, SK1 (KCNN1), was recently cloned. Here we describe the gene structure of KCNN1 and its localization by radiation hybrid mapping to chromosome 19p13.1.

Animals↗
PubMed1995

Potential genotoxic risk related to simultaneous exposure to radionuclides and cytostatics.

The aim of the study was to evaluate the genotoxic risk to medical personnel concurrently exposed to ionizing radiation and antineoplastics, using changes in their lymphocyte cell genome as a bioindicator. The study comprised 12 female nurses employed in the nuclear medicine hospital department and an equal number of matched controls. For each examinee, both conventional structural chromosomal aberration analysis and sister chromatid exchange test (SCE) were carried out. According to Student's t-test, neither the incidence of structural chromosomal aberrations (p > 0.6) nor the mean SCE-frequency rate (p > 0.3) were significantly increased among the exposed subjects. Nevertheless, in those exposed, irreparable chromosomal damages and wide SCE-ranges were observed. Such findings suggest the possibility of genotoxic implications of concurrent occupational exposure to ionizing radiation and antineoplastic drugs.

Adult↗
PubMed1991

Differentiation-dependent alteration in the chromatin structure of chromosomal protein HMG-17 gene during erythropoiesis.

The expression of the gene coding for chromosomal protein HMG-17 is down regulated during chicken erythrocyte maturation. The transcriptional down regulation is associated with major alterations in the chromatin structure of this gene. The 5' region of the gene contains both constitutive and developmental stage-specific deoxyribonuclease I (DNase I) hypersensitive sites. The constitutive sites bracket the "CpG island" present in the gene, which remains hypomethylated throughout the various developmental stages. During erythropoiesis, the gene acquires a distinct structure that, upon digestion with micrococcal nuclease (MNase) yields an unusual repeat. Two nucleosomes, with a 200 base-pair repeat, are positioned immediately downstream from the start of transcription. Immediately downstream and upstream from these nucleosomes, the boundaries between MNase sites change to a 75 base-pair repeat, which indicates an unusual chromatin structure. The differentiation related changes in the DNase I and MNase digestion pattern in the 5' region of the gene suggest that sequences present in the first intron may be involved in gene regulation. The results may be relevant to the regulation of the entire HMG-14/-17 gene family.

Animals↗
PubMed2004

Microarray analysis of transposition targets in Escherichia coli: the impact of transcription.

Transposable elements have influenced the genetic and physical composition of all modern organisms. Defining how different transposons select target sites is critical for understanding the biochemical mechanism of this type of recombination and the impact of mobile genes on chromosome structure and function. Phage Mu replicates in Gram-negative bacteria using an extremely efficient transposition reaction. Replicated copies are excised from the chromosome and packaged into virus particles. Each viral genome plus several hundred base pairs of host DNA covalently attached to the prophage right end is packed into a virion. To study Mu transposition preferences, we used DNA microarray technology to measure the abundance of >4,000 Escherichia coli genes in purified Mu phage DNA. Insertion hot- and cold-spot genes were found throughout the genome, reflecting >1,000-fold variation in utilization frequency. A moderate preference was observed for genes near the origin compared to terminus of replication. Large biases were found at hot and cold spots, which often include several consecutive genes. Efficient transcription of genes had a strong negative influence on transposition. Our results indicate that local chromosome structure is more important than DNA sequence in determining Mu target-site selection.

Bacteriophage mu↗
PubMed2001

Chromatin and chromosomal fine structure in spermatogenesis of some species of amphibians.

Spermatogenesis is a complex differentiation process which is characterised, among other features, by conspicuous stage-specific nuclear events such as the pairing of homologous chromosomes coupled with the formation of synaptonemal complexes, the replacement of histones with sperm-specific proteins during spermiogenesis and, as a result, chromatin condensation and its inactivation in sperm cells. The chromatin of spermatogenic cells undergoes dramatic conformational changes upon differentiation from spermatogonia to mature spermatozoa. During the haploid stage of spermatogenesis, histones are gradually replaced, firstly by transition proteins and later by sperm-specific proteins. As a result of the high degree of condensation and inactivation of spermatid and sperm chromatin, Sertoli cells are responsible for the nourishment of germ cells with ribosomal RNA and nutritive substances.

Amphibians↗
PubMed1990

[Role of chromosome aberrations in the development of leukemic process].

The pathogenetic and clinical significance of karyotype features in leukemia and preleukemia are analysed. In 34.7 per cent patients with preleukemia, karyotype instability was observed which consisted in numerical and structural chromosome aberrations with clone anomaly. It was found that karyotype instability is an initial stage of anomalous clone formation and often precedes its development in preleukemia, secondary leukemias, and in preblastic stage of chronic myeloid leukemia. Acute leukemias were found to be characterized by premeditated numerical and structural chromosomal aberrations with predominant involvement of chromosomes 5, 7, 8, and 21 in non-lymphoblastic and chromosomes 6, 9, 8, and 21 in lymphoblastic forms of acute leukemia. It was also shown that the normal to abnormal metaphase ratio in acute leukemia patients is of high prognostic value.

Chromosome Aberrations↗
PubMed1992

Human long-chain acyl-CoA synthetase: structure and chromosomal location.

A complementary DNA clone encoding the entire human long-chain acyl-CoA synthetase was isolated and the total 698-amino acid sequence was deduced. The amino acid sequence of human long-chain acyl-CoA synthetase shows 84.9% identity to that of rat long-chain acyl-CoA synthetase. The nucleotide sequences of the protein coding regions between human and rat long-chain acyl-CoA synthetase mRNAs are highly conserved (85.6%), whereas those of the 3' untranslated regions are less conserved (72%). The location of the human long-chain acyl-CoA synthetase gene was identified on chromosome 4 by spot hybridization of flow-sorted chromosomes. Computer-assisted homology search revealed a significant similarity of the enzyme with the enzymes of the luciferase family. Based on this similarity, the structure of human long-chain acyl-CoA synthetase can be divided into five domains: the N-terminus, two domains similar to those in enzymes of the luciferase family, a long gap region between the similar domains and the C-terminus.

Amino Acid Sequence↗