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Results for “Repetitive Sequences, Nucleic Acid”

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PubMed2005

Comparative analysis of chromatin landscape in regulatory regions of human housekeeping and tissue specific genes.

BACKGROUND: Global regulatory mechanisms involving chromatin assembly and remodelling in the promoter regions of genes is implicated in eukaryotic transcription control especially for genes subjected to spatial and temporal regulation. The potential to utilise global regulatory mechanisms for controlling gene expression might depend upon the architecture of the chromatin in and around the gene. In-silico analysis can yield important insights into this aspect, facilitating comparison of two or more classes of genes comprising of a large number of genes within each group. RESULTS: In the present study, we carried out a comparative analysis of chromatin characteristics in terms of the scaffold/matrix attachment regions, nucleosome formation potential and the occurrence of repetitive sequences, in the upstream regulatory regions of housekeeping and tissue specific genes. Our data show that putative scaffold/matrix attachment regions are more abundant and nucleosome formation potential is higher in the 5' regions of tissue specific genes as compared to the housekeeping genes. CONCLUSION: The differences in the chromatin features between the two groups of genes indicate the involvement of chromatin organisation in the control of gene expression. The presence of global regulatory mechanisms mediated through chromatin organisation can decrease the burden of invoking gene specific regulators for maintenance of the active/silenced state of gene expression. This could partially explain the lower number of genes estimated in the human genome.

Cell Nucleus↗

PubMed1989

Human desmin-coding gene: complete nucleotide sequence, characterization and regulation of expression during myogenesis and development.

A recombinant clone encoding for the human desmin gene (des) has been isolated and characterized and its complete nucleotide sequence has been determined. The 8.4-kb gene has nine exons separated by introns ranging in size from 0.1-2.2 kb. Comparison of the human des gene with that of the hamster has shown that there is a full correspondence in position, size and sequence of the exons. There are eight introns in both the human and the hamster des genes. Although the nucleotide sequence of the introns reveals a large divergence, splice junction sequence signals are conserved. A particularly striking feature of the human des gene is the 1.2-kb repetitive sequence found in the introns. These sequences all belong to the human AluI family. When the 5'- and 3'-untranslated regions of the human vim and des genes were compared it was found that there was a 16-mer consensus element similar to that described by Quax et al. [Cell 43 (1985) 327-338] for the hamster and an 11-bp sequence with homology to the distal regulatory sequence of human and mouse alpha-cardiac actin-coding genes [Minty and Kedes, Mol. Cell. Biol. 6 (1986) 2125-2136] in the 5'-flanking region. The 3'-untranslated region of the human des gene was found to be conserved when compared to the hamster des gene. Only one species of desmin RNA of 2.2 kb was found in human striated and smooth muscle both in vivo and in vitro.

Amino Acid Sequence↗

PubMed1991

Structural organization and complete sequence of the human alpha-N-acetylgalactosaminidase gene: homology with the alpha-galactosidase A gene provides evidence for evolution from a common ancestral gene.

Human alpha-N-acetylgalactosaminidase (alpha-GalNAc; EC 3.2.1.49), the lysosomal glycohydrolase that cleaves alpha-N-acetylgalactosaminyl moieties in glycoconjugates, is encoded by a gene localized to chromosome 22q13----qter. The deficient activity of this enzyme results in Schindler disease, an autosomal recessive disorder characterized by the increased urinary excretion of glycopeptides and oligosaccharides containing alpha-N-acetylgalactosaminyl moieties. Recently, the 3.6-kb full-length alpha-GalNAc cDNA sequence was isolated and found to have remarkable nucleotide and predicted amino acid homology (55.8 and 46.9%, respectively) with the human alpha-galactosidase A (alpha-Gal A) cDNA. To investigate the possible evolutionary relatedness of the two glycosidases, the alpha-GalNAc chromosomal gene was isolated and characterized. Screening of a human genomic DNA cosmid library resulted in the identification of a clone, gAGB-1, with an approximately 35-kb insert that contained the entire alpha-GalNAc gene. A single approximately 15-kb EcoRI fragment of gAGB-1, which contained the complete 3.6-kb cDNA sequence, was digested and the subcloned fragments were sequenced in both orientations. The 13,709-bp alpha-GalNAc gene had nine exons ranging from 95 to 2028 bp and intronic sequences of 304 to 2684 bp. All exon/intron junctions conformed to the GT/AG consensus rule. Analysis of 1.4 kb of 5' flanking sequence revealed three Sp1 and two CAAT-like promoter elements. This region was GC-rich (56%), but no HTF island was identified. The gene contained six Alu-repetitive elements, all in the reverse orientation. Comparison of the structural organization of the alpha-GalNAc and the alpha-Gal A genes revealed that all six alpha-Gal A introns were identically positioned in the homologous alpha-GalNAc exonic sequence. Two additional introns, 1 and 8, were identfied in the alpha-GalNAc gene. The predicted amino acid sequences of alpha-GalNAc exons 2 through 7 and those of corresponding alpha-Gal A exons 1 through 6 were 46.2 to 62.7% identical. In contrast, there was little, if any, similarity between the deduced amino acid sequences of alpha-Gal A exon 7 and alpha-GalNAc exons 8 and 9. The remarkable amino acid identity and the identical exonic interruption by six introns of the alpha-GalNAc and alpha-Gal A genes suggest that this region in both genes is evolutionarily related and arose through duplication and divergence from a common ancestral gene.

Base Sequence↗

PubMed1989

Nucleotide sequence of the rat gamma-crystallin gene region and comparison with an orthologous human region.

The sequences of a 51-kb region containing the cluster of five rat gamma-crystallin-coding genes (CRYG) and of a 7-kb region surrounding the sixth rat CRYG gene were determined. Approximately 78% of the total sequence represents intergenic DNA. We also sequenced 22 kb of DNA from the human CRYG gene cluster. All CRYG genes are associated with CpG-rich regions. The sequence similarity between the human and rat gene regions drops sharply (to 65%) in intronic and 3'-flanking regions but decreases only gradually in the 5'-flanking region. Highly conserved regions (greater than 80%) are found as far upstream as 1.5 kb. Overall intergenic distances are conserved. The human region contains much more repetitive DNA (24% vs. 10%) but less simple-sequence (sps) DNA (0.7% vs. 4%) than the rat region. Almost all repeats and spsDNA elements are located in the intergenic region. The location of repetitive and spsDNA differs between the orthologous regions and these elements were probably inserted after the evolutionary separation of rat and man. The Alu repeats in man and the B3 repeats in the rat are close copies of their respective consensus sequences and bordered by virtually perfect repeats. In contrast, the B1 and B2 repeats in the rat have diverged considerably from the consensus sequence and the surrounding direct repeats are usually imperfect. Thus the dispersion of the B1 and B2 repeats in the rat probably preceded that of the B3 repeats. Within the rat genomic region the spacing of Z-DNA elements is surprisingly regular, they are located about 12 kb apart. A search for putative matrix-associated regions suggests that the rat CRYG gene cluster is organized into two chromosomal domains.

Animals↗

PubMed2005

Structure, expression, and transcriptional regulation of the Strongylocentrotus franciscanus spec gene family encoding intracellular calcium-binding proteins.

The mechanisms by which gene expression patterns emerge during evolution are poorly understood. The sea urchin spec genes offer a useful means to investigate evolutionary mechanisms. Genes of the spec family from Strongylocentrotus purpuratus and Lytechinus pictus have identical patterns of aboral ectoderm-specific expression but exhibit species-specific differences in copy number, genomic structure, temporal expression, and cis-regulatory architecture. Here, we identify spec genes from a phylogenetic intermediate, Strongylocentrotus franciscanus, to gain insight into the evolution of the spec gene family and its transcriptional regulation. We identified two spec genes in the S. franciscanus genome, sfspec1a and sfspec1b, that were orthologous to spec1 from S. purpuratus. sfspec1b transcripts began to accumulate at the blastula stage and became progressively more abundant; this was reminiscent of spec expression in L. pictus but different from that in S. purpuratus. As expected, sfspec1b expression was restricted to aboral ectoderm cells. The six-exon structure of the sfspec1b genomic locus was identical to that of the S. purpuratus spec genes and was bounded by two repeat-spacer-repeat (RSR) repetitive sequence elements, which are conserved features of S. purpuratus spec genes and function as transcriptional enhancers. The enhancer activity of the sfspec1b RSRs was comparable to that of their S. purpuratus counterparts, although the placement and orientation of crucial cis-regulatory elements within the RSRs differed. We discovered a spec gene in S. franciscanus that was only distantly related to other spec genes but was highly conserved in S. purpuratus. Unexpectedly, this gene was expressed exclusively in endoderm lineages. Our results show that the evolution of spec cis-regulatory elements is highly dynamic and that substantial alterations can occur when maintaining or grossly modifying gene expression patterns.

Amino Acid Sequence↗

PubMed2000

Binding of octamer factors to a novel 3'-positive regulatory element in the mouse interleukin-5 gene.

The development of eosinophilia is regulated by interleukin (IL)-5. The biological specificity of eosinophilia suggests a tight and independent regulation of IL-5 expression. A number of regulatory regions in the 5'-end of the IL-5 gene have been described; many of them are involved in the regulation of other genes, and it is not clear how the specific expression of IL-5 is regulated. In this study, we report the finding of a novel 3'-regulatory element. Data base analysis of a 2-kilobase fragment of the 3'-end of the mouse IL-5 gene revealed the presence of a 40-base pair-long repetitive sequence that consists of four direct repeats of ATGAATGA distributed in a symmetrical manner. This sequence, named mouse downstream regulatory element-1 (mDRE1), was shown to be protected in DNase I footprinting assays in vitro. Electrophoretic mobility shift assays using specific antibodies identified the transcription factors Oct-1 and Oct-2 as responsible for the formation of the specific complexes with mDRE1 and nuclear extracts from both EL4 and primary T-cells. Competition electrophoretic mobility shift assays with oligonucleotides containing different numbers of ATGAATGA repeats showed that Oct-1 and Oct-2 bind to different motifs in the mDRE1 sequence. Deletion of mDRE1 from a 9.5-kilobase IL-5 gene construct significantly decreased the expression of the luciferase reporter gene, suggesting that it plays a positive role in the expression of the IL-5 gene.

Animals↗

PubMed1995

Reverse transcriptase: mediator of genomic plasticity.

Reverse transcription has been an important mediator of genomic change. This influence dates back more than three billion years, when the RNA genome was converted into the DNA genome. While the current cellular role(s) of reverse transcriptase are not yet completely understood, it has become clear over the last few years that this enzyme is still responsible for generating significant genomic change and that its activities are one of the driving forces of evolution. Reverse transcriptase generates, for example, extra gene copies (retrogenes), using as a template mature messenger RNAs. Such retrogenes do not always end up as nonfunctional pseudogenes but form, after reinsertion into the genome, new unions with resident promoter elements that may alter the gene's temporal and/or spatial expression levels. More frequently, reverse transcriptase produces copies of nonmessenger RNAs, such as small nuclear or cytoplasmic RNAs. Extremely high copy numbers can be generated by this process. The resulting reinserted DNA copies are therefore referred to as short interspersed repetitive elements (SINEs). SINEs have long been considered selfish DNA, littering the genome via exponential propagation but not contributing to the host's fitness. Many SINEs, however, can give rise to novel genes encoding small RNAs, and are the migrant carriers of numerous control elements and sequence motifs that can equip resident genes with novel regulatory elements [Brosius J. and Gould S.J., Proc Natl Acad Sci USA 89, 10706-10710, 1992]. Retrosequences, such as SINEs and portions of retroelements (e.g., long terminal repeats, LTRs), are capable of donating sequence motifs for nucleosome positioning, DNA methylation, transcriptional enhancers and silencers, poly(A) addition sequences, determinants of RNA stability or transport, splice sites, and even amino acid codons for incorporation into open reading frames as novel protein domains. Retroposition can therefore be considered as a major pacemaker for evolution (including speciation). Retroposons, with their unique properties and actions, form the molecular basis of important evolutionary concepts, such as exaptation [Gould S.J. and Vrba E., Paleobiology 8, 4-15, 1982] and punctuated equilibrium [Elredge N. and Gould S.J. in Schopf T.J.M. (ed). Models in Paleobiology. Freeman, Cooper, San Francisco, 1972, pp. 82-115].

Animals↗

PubMed1995

Origin of a negative calcium response element in an ALU-repeat: implications for regulation of gene expression by extracellular calcium.

The negative calcium response element type 2 (nCARE) is a regulatory DNA sequence consisting of a palindromic core sequence and several upstream T residues, which was originally described in the 5' flank of the human PTH gene. The nCARE functions in an orientation-specific manner to inhibit PTH transcription in response to raised extracellular calcium levels. Here we report that the PTH nCARE lies within a hitherto unrecognized ALU-like element situated approximately 3.6 kB upstream of the human PTH gene transcriptional start site. Since ALU elements are repetitive DNA sequences, which are widely distributed throughout the human genome, we hypothesized that other nCARE elements might also exist. A search of the GenBank/EMBL databases with the nCARE core sequence confirmed this to be the case showing the presence of 111 copies of the nCARE in human/primate sequences. Analysis of the 7SL RNA sequence from which ALU elements derive also showed the presence of an nCARE "core" sequence immediately upstream of the poly-A+ tail. These data suggest that the nCARE is derived from retrotransposition of 7SL RNA and forms an integral part of many ALU elements; reverse transcription of the poly-A+ tail of 7SL RNA adds T residues, which on retrotransposition into genomic DNA with the core sequence, forms an ALU element containing a functional nCARE. Some of the genes associated with nCARE elements express products which are affected by extracellular calcium concentrations and work is in progress to determine the functional effects of nCARE at these sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗

PubMed2002

CENP-B box is required for de novo centromere chromatin assembly on human alphoid DNA.

Centromere protein (CENP) B boxes, recognition sequences of CENP-B, appear at regular intervals in human centromeric alpha-satellite DNA (alphoid DNA). In this study, to determine whether information carried by the primary sequence of alphoid DNA is involved in assembly of functional human centromeres, we created four kinds of synthetic repetitive sequences: modified alphoid DNA with point mutations in all CENP-B boxes, resulting in loss of all CENP-B binding activity; unmodified alphoid DNA containing functional CENP-B boxes; and nonalphoid repetitive DNA sequences with or without functional CENP-B boxes. These four synthetic repetitive DNAs were introduced into cultured human cells (HT1080), and de novo centromere assembly was assessed using the mammalian artificial chromosome (MAC) formation assay. We found that both the CENP-B box and the alphoid DNA sequence are required for de novo MAC formation and assembly of functional centromere components such as CENP-A, CENP-C, and CENP-E. Using the chromatin immunoprecipitation assay, we found that direct assembly of CENP-A and CENP-B in cells with synthetic alphoid DNA required functional CENP-B boxes. To the best of our knowledge, this is the first reported evidence of a functional molecular link between a centromere-specific DNA sequence and centromeric chromatin assembly in humans.

Autoantigens↗

PubMed1998

Evidence of multiple transcription initiation and termination sites within the rDNA intergenic spacer and rRNA readthrough transcription in the urochordate Herdmania curvata.

Analysis of the structure of the urochordate Herdmania curvata ribosomal DNA intergenic spacer (IGS) and its role in transcription initiation and termination suggests that rRNA gene regulation in this chordate differs from that in vertebrates. A cloned H. curvata IGS is 1881 bp and composed predominantly of two classes of similar repeat sequences that largely alternate in a tandem array. Southern blot hybridization demonstrates that the IGS length variation within an individual and population is largely the result of changes in internal repeat number. Nuclease S1 mapping and primer extension analyses suggest that there are two transcription initiation sites at the 3' end of the most 3' repetitive element; these sites are 6 nucleotides apart. Unlike mouse, Xenopus, and Drosophila, there is no evidence of transcription starting elsewhere in the IGS. Most sequence differences between the promoter repeat and the other internal repeats are in the vicinity of the putative initiation sites. As in Drosophila, nuclease S1 mapping of transcription termination sites suggest that there is not a definitive stop site and a majority of the pre-rRNAs read through a substantial portion of the IGS. Some transcription appears to proceed completely through the promoter repeat into the adjacent rDNA unit. Analysis of oocyte RNA by reverse transcription-polymerase chain reaction (RT-PCR) confirms that readthrough transcription into the adjacent rDNA unit is occurring in some small IGS length variants; there is no evidence of complete readthrough of IGSs larger than 1.0 kb.

Animals↗

PubMed1988

Molecular study of the retrovirus-like transposable element 412, a 20-OH ecdysone responsive repetitive sequence in Drosophila cultured cells.

Used at a physiological concentration, the steroid hormone 20-hydroxyecdysone (20-OHE) induces, in Kc cultured Drosophila melanogaster cells, important and specific changes. Modifications occur at morphological and enzymatical levels. Variations in specific protein synthesis are observed. At the molecular level, 20-OHE particularly induces a decrease in expression of the mobile dispersed genetic element 412. This repeated element which belongs to the "copia-like" family is more widely represented in Kc cells (80 fold) compared to fly cells (25 fold). 412 transcripts are heterogeneous in size, essentially polyadenylated and restricted to the nucleus. A minimal concentration of 10(-8) M and a time treatment of 16 hours are necessary to obtain a strong decrease in 412 expression. The decrease is at least an effect on these sequences at the transcriptional level. Structural similarities between the 412 element and the proviral forms of vertebrate retroviruses are strengthened by the characterization of extrachromosomal circular DNA forms revealed by the 412 probe. Quantifying experiments have shown that the steady state level of such forms is not affected by the steroid treatment.

Animals↗

PubMed2003

Genomic characterization of a repetitive motif strongly associated with developmental genes in Drosophila.

BACKGROUND: Non-coding DNA represents a high proportion of all metazoan genomes. Although an undetermined fraction of this DNA may be considered devoid of any function, it also contains important information residing in specific cis-regulatory sequences. RESULTS: We report a 27 bp motif that is overrepresented within the fly genome. This motif does not show any significant similarity with transposon sequences and is strongly associated with genes involved in development and/or signal transduction. The 27 bp motif is preferentially located within introns, and has a tendency to be present in multiple copies around genes. Furthermore, it is often found embedded in known non-coding regulatory regions. The regulatory network defined by this motif is partially shared in D. pseudoobscura. CONCLUSION: We have identified a 27 bp cis-regulatory sequence widely distributed within the Drosophila genome in association with developmental genes. This motif may be very useful towards the annotation of functional regulatory regions within the Drosophila genome and the construction of regulatory networks of Drosophila development.

Animals↗

PubMed1989

Sequence organization in regulatory regions of DNA of minute virus of mice.

Analysis of the nucleotide sequence of minute virus of mice (MVM) DNA indicates that the DNA termini contain clusters of potential DNA regulatory elements and that there are repetitive DNA elements highly reiterated throughout the entire genome, which may also have a role in DNA function. The left end of MVM DNA, which contains the promoter for the nonstructural genes, has a cluster of DNA elements that includes homologies to the polyoma virus enhancer, three copies of an E1A-inducible transcription factor (ATF) binding site, and a potential Z-DNA element. The MVM right end, which contains the origin of DNA replication, has a cluster of DNA elements that includes several homologies to the polyoma virus replication origin and a potential Z-DNA element. In addition, oligonucleotide frequency analysis indicates the presence of highly recurring sequence elements throughout the entire MVM genome that may be involved in regulation. This computer-aided analysis suggests similarities and significant differences in regulatory sequence organization between MVM and polyoma virus, and identifies specific DNA elements for future genetic characterization.

Activating Transcription Factors↗

PubMed1993

cis regulation of the keratin 18 gene in transgenic mice.

The gene coding for human keratin 18 (K18), a type I intermediate filament protein found in a variety of simple epithelia, is regulated correctly in transgenic mice but is promiscuously expressed after direct transfection into cell culture lines. We have begun an investigation of the mechanisms responsible for the correct regulation of K18 with a comparison of the chromatin state of K18 in permissive and nonpermissive transgenic mouse tissues to identify seven expression-specific, DNase-hypersensitive sites that correlate with known or potential regulatory regions of the gene. Four of these sites are associated with the proximal promoter region and the first intron that has been implicated previously in the transcriptional control of K18. Two hypersensitive sites are associated with a conserved Alu repetitive sequence located immediately upstream of the proximal promoter elements. Transcription of this Alu element in a direction opposite that of K18 was correlated with K18 expression in transgenic tissues. The final hypersensitive site was mapped to exon 6. The potential importance of this region for the expression of K18 was supported by the results of transient expression of the gene and various deleted constructions. In addition, exon 6 and the intron 1 regulatory region were distinguished from the remainder of K18 by differential DNA methylation in expressing and nonexpressing tissues. The CpG-rich proximal promoter and first exon regions remain unmethylated in both permissive and nonpermissive tissues. These results suggest that DNA methylation is not the primary mechanism of control of the gene. An Alu RNA polymerase III transcription unit and exon 6 are implicated in regulation of K18.

Amino Acid Sequence↗

PubMed1996

Complete structure of the human alpha-albumin gene, a new member of the serum albumin multigene family.

The nucleotide sequence of the human alpha-albumin gene, including 887 bp of the 5'-flanking region and 1311 bp of the 3-flanking region (24,454 in total), was determined from three overlapping lambda phage clones. The sequence spans 22,256 bp from the cap site to the polyadenylylation site, revealing a gene structure of 15 exons separated by 14 introns. The methionine initiation codon ATG is within exon 1; the termination codon TGA is within exon 14. Exon 15 is entirely untranslated and contains the polyadenylylation signal AATAAA. The deduced polypeptide chain is composed of a 21-amino-acid leader peptide, followed by 578 amino acids of the mature protein. There are seven repetitive DNA elements (Alu and Kpn) in the introns and 3-flanking region. The sizes of the 15 alpha-albumin exons match closely those of the albumin, alpha-fetoprotein, and vitamin D-binding protein genes. The exons are symmetrically placed within the three domains of the individual proteins, and they share a characteristic codon splitting pattern that is conserved among members of the gene family. The results provide strong evidence that alpha-albumin belongs to, and most likely completes with, the serum albumin gene family. Based on structural similarity, alpha-albumin appears to be most closely related to alpha-fetoprotein. The complete structure of this family of four tandemly linked genes provides a well-characterized approximately 200 kb locus in the 4q subcentromeric region of the human genome.

Albumins↗

PubMed1992

Identification of an internal cis-element essential for the human L1 transcription and a nuclear factor(s) binding to the element.

L1 (LINE-1) is a long interspersed repetitive sequence derived from a retrotransposon. Transfection studies using the CAT gene as a reporter demonstrated that the first 155bp in the human L1 sequence contains an element(s) responsible for the promoter activity in HeLa cells. The transcription was shown to initiate at the first nucleotide of the L1 sequence in the transgene. Three prominent nuclear protein binding sites were found in the 5' region of the L1 sequence by DNaseI footprint analysis. One of the binding sites, designated as site A located at +3 to +26, was shown to be essential for the L1 transcription because the mutation at the site A caused almost complete loss of the promoter activity. A sequence AAGATGGCC at +11 to +19 in the site A was defined as a target core element for the protein binding. The site A-binding protein (designated TFL1-A) was found in various types of cells including an embryonic teratocarcinoma cell line. These results indicate that an internal short element located at the very 5' terminal of L1 sequence and the nuclear factor binding to the element play a crucial role in the transcription of human L1.

Amino Acid Sequence↗

PubMed1995

The consensus sequence of a major Alu subfamily contains a functional retinoic acid response element.

Alu repeats are interspersed repetitive DNA elements specific to primates that are present in 500,000 to 1 million copies. We show here that an Alu sequence encodes functional binding sites for retinoic acid receptors, which are members of the nuclear receptor family of transcription factors. The consensus sequences for the evolutionarily recent Alu subclasses contain three hexamer half sites, related to the consensus AGGTCA, arranged as direct repeats with a spacing of 2 bp, which is consistent with the binding specificities of retinoic acid receptors. An analysis was made of the DNA binding and transactivation potential of these sites from an Alu sequence that has been previously implicated in the regulation of the keratin K18 gene. These Alu double half sites are shown to bind bacterially synthesized retinoic acid receptors as assayed by electrophoretic mobility shift assays. These sites are further shown to function as a retinoic acid response element in transiently transfected CV-1 cells, increasing transcription of a reporter gene by a factor of approximately 35-fold. This transactivation requires cotransfection with vectors expressing retinoic acid receptors, as well as the presence of all-trans-retinoic acid, which is consistent with the known function of retinoic acid receptors as ligand-inducible transcription factors. The random insertion of potentially thousands of Alu repeats containing retinoic acid response elements throughout the primate genome is likely to have altered the expression of numerous genes, thereby contributing to evolutionary potential.

Animals↗

PubMed1994

Enhancer function of a 53-bp repetitive element in the 5' flanking region of the human neutrophil elastase gene.

Expression of the human neutrophil elastase (NE) gene is limited to the early stage of myeloid cell differentiation in bone marrow cells. While NE gene expression is controlled mainly at the transcriptional level during bone marrow cell differentiation, the mechanism of transcriptional control is not fully understood. One motif of interest in the 5' flanking region of the gene is the six tandem repeats of a 53-bp nucleotide sequence (REP53) containing a potential binding site for a basic helix-loop-helix protein located at -1032 to -716. The REP53 sequence can function as a non-cell specific transcriptional enhancer which is capable of augmenting heterologous promoter activity. When the single REP53 element was inserted into the pAZ1037 chloramphenicol acetyltransferase (CAT) expression vector immediately upstream of the chicken beta-actin promoter in either normal or inverted orientation and used to transfect K-562 erythroleukemia or HeLa cervical carcinoma cells, these modified vectors achieved 2 to 3-fold higher CAT activity than the parental pAZ1037 vector irrespective of orientation of the REP53.

Animals↗