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At least 289 records · Page 16Linked to original sources
PubMed1999

SufS is a NifS-like protein, and SufD is necessary for stability of the [2Fe-2S] FhuF protein in Escherichia coli.

Escherichia coli fhuF mutants, a sufS::MudI mutant, and a sufD::MudI mutant were found to have the same phenotype: the inability to use ferrioxamine B as an iron source in a plate assay. In addition, the sufS and sufD genes were shown to be regulated by the iron-dependent Fur repressor. Sequence analysis revealed that the sufS open reading frame corresponds to orf f406. The protein SufS belongs to the family of NifS-like proteins, which supply sulfur for [Fe-S] centers. The protein FhuF contains a [2Fe-2S] center. A mutation in the upstream sufD gene (orf f423) caused the same phenotype. The T7 expression system and a His tag allow the isolation in good yield of the FhuF protein from a wild-type strain. In contrast, overproduction of the protein in a DeltasufD strain failed. Radioactive labeling of N-His-FhuF with [35S]methionine showed that the protein was unstable in the DeltasufD mutant.

Amino Acid Sequence↗
PubMed2000

Identification and molecular characterization of two novel Trypanosoma cruzi genes encoding polypeptides sharing sequence motifs found in proteins involved in RNA editing reactions.

We have previously identified a Trypanosoma cruzi cDNA encoding a protein named Tc52 sharing structural and functional properties with the thioredoxin and glutaredoxin protein family involved in thiol-disulphide redox reactions. Furthermore, we reported that Tc52 also plays a role in T. cruzi-associated immunosuppression observed during Chagas' disease. Moreover, Tc52 gene targeting deletion strategy allowed us to demonstrate that monoallelic disruption of Tc52 resulted in the alteration of the metacyclogenesis process and the production of less virulent parasites. Sequence analysis of a 7358 bp genomic fragment containing the Tc52 encoding gene revealed two additional open reading frames (ORF-A and C). The ORFs are likely to have protein coding function by a number of criteria, including reverse transcriptase polymerase chain reaction (RT-PCR), Western blot and immunofluorescence analyses. The deduced amino-acid (aa) sequence of the ORF-A localized upstream of the Tc52 gene revealed that it contains within its N-terminus (aa 1 to 170) four RGG boxes known to act as RNA binding motifs in some proteins that interact with RNA, interspersed with a high density of glycine with regular spacing of tryptophan (WX(9-10)) in which X is often a glycine. Moreover, the C-terminal part of the ORF-C (aa 253-289) contains a motif that is strikingly similar (7-35% identity, 14-46% similarity over 28aa) to a short sequence (RNP1) comprising the consensus sequence RNA binding domain (CS-RBD) found in a number of proteins that interact with RNA. The aa sequence from the ORF-C localized downstream of the Tc52 gene showed significant homology to human adenosine deaminase acting on RNA (hADAT1) that specifically deaminates adenosine 37 to inosine in eukaryotic tRNA(Ala) and to its homologue yeast protein (Tad1p) (22-25% identity and an additional 38-40% similarity over 177aa). Moreover, highly similar motifs of the deaminase domain are present in the T. cruzi ORF-C. Furthermore, the 5' flanking regions of the genes contained repeat TATA and CAAT nucleotide sequences which resemble the motifs found upstream of the transcription initiation sites in eukaryotic promoters. Therefore, the characterization of novel T. cruzi genes encoding proteins which show similarity to components of RNA processing reactions provides new tools to investigate the gene expression regulation in these parasitic organisms. Moreover, our recent findings on the Tc52 encoding gene underline the interest of genetic manipulation of T. cruzi, not only making it possible to use more closely an in vitro approach to find out how genes function, but also to obtain 'attenuated' strains that could be used in the development of vaccinal strategies.

Adenosine Deaminase↗
PubMed1993

Characterization of the gene coding for the Rickettsia prowazekii DNA primase analogue.

The gene (dnaG) coding for DNA primase in the obligate intracellular parasitic bacterium, Rickettsia prowazekii, has been isolated and characterized. An open reading frame (ORF) of 1848 bp capable of encoding 616 amino acids (aa) is located 18 bp upstream from the gene coding for the major sigma factor of R. prowazekii, sigma 73. Based on aa sequence comparisons of DNA primase from R. prowazekii, Escherichia coli, Salmonella typhimurium and Bacillus subtilis, we propose that R. prowazekii dnaG begins 69 bp into the ORF and encodes 593 aa with a calculated M(r) of 68,683. An upstream ORF overlaps 66 of the first 69 bp of the larger R. prowazekii dnaG ORF, suggesting either an overlapping gene structure or the generation of the smaller protein product of 593 aa. Predicted aa sequence of R. prowazekii primase compared to E. coli, S. typhimurium and B. subtilis primases reveals 30.5%, 30.5% and 29.7% aa identity, respectively. The R. prowazekii dnaG gene failed to complement an E. coli dnaG temperature sensitive mutation perhaps due to poor expression of the gene or inability to function properly in E. coli. The gene organization of an ORF followed by DNA primase (dnaG) and then the major sigma factor (rpoD) is consistent with the major macromolecular synthesis operons of E. coli, S. typhimurium and B. subtilis.

Amino Acid Sequence↗
PubMed2001

Genetic analysis of exfoliative toxin A-producing Staphylococcus aureus isolated from mastitic cow's milk.

Exfoliative toxin A (ETA), produced by Staphylococcus aureus, is the causative agent of staphylococcal scalded-skin syndrome (SSSS) in children. Recently, we reported that ETA was detected by reverse passive latex agglutination in three isolates of S. aureus from cow's milk, but that these ETA-positive isolates did not cause the so-called Nikolsky sign in neonatal mice. In this study, therefore, the eta gene encoding ETA and regulatory genes of these bovine isolates were analyzed by the polymerase chain reaction (PCR) and sequencing. The eta gene was amplified from three bovine isolates by PCR and their resulting nucleotide sequences found to correspond to the eta gene from the human isolate, except for three nucleotides in the upstream region of the eta open reading frame (ORF). An accessory gene regulator (agr), which is a global regulatory locus, was detected in these bovine isolates by PCR amplification. In addition, the ORF (J-4), located 120 bp upstream from the eta ORF of the human isolate, was also amplified from these bovine isolates, with their nucleotide sequences differing at 32 positions from the human isolate. Bovine and human ORF J-4 equally enhanced production of ETA in the recombinants of the eta gene, suggesting that the variation in bovine ORF J-4 may be not be the cause of the difference in amount of ETA produced by bovine and human isolates.

Animals↗
PubMed1999

In vivo expression of the nucleolar group I intron-encoded I-dirI homing endonuclease involves the removal of a spliceosomal intron.

The Didymium iridis DiSSU1 intron is located in the nuclear SSU rDNA and has an unusual twin-ribozyme organization. One of the ribozymes (DiGIR2) catalyses intron excision and exon ligation. The other ribozyme (DiGIR1), which along with the endonuclease-encoding I-DirI open reading frame (ORF) is inserted in DiGIR2, carries out hydrolysis at internal processing sites (IPS1 and IPS2) located at its 3' end. Examination of the in vivo expression of DiSSU1 shows that after excision, DiSSU1 is matured further into the I-DirI mRNA by internal DiGIR1-catalysed cleavage upstream of the ORF 5' end, as well as truncation and polyadenylation downstream of the ORF 3' end. A spliceosomal intron, the first to be reported within a group I intron and the rDNA, is removed before the I-DirI mRNA associates with the polysomes. Taken together, our results imply that DiSSU1 uses a unique combination of intron-supplied ribozyme activity and adaptation to the general RNA polymerase II pathway of mRNA expression to allow a protein to be produced from the RNA polymerase I-transcribed rDNA.

Amoeba↗
PubMed1995

Characterisation of the yenI/yenR locus from Yersinia enterocolitica mediating the synthesis of two N-acylhomoserine lactone signal molecules.

Yersinia enterocolitica produces compounds capable of transcriptionally activating the Photobacterium fischeri bioluminescence (lux) operon. Using high-performance liquid chromatography, high resolution tandem mass spectrometry in conjunction with chemical synthesis, two signal molecules were identified and shown to be N-hexanoyl-L-homoserine lactone (HHL) and N-(3-oxohexanoyl)-L-homoserine lactone (OHHL). A gene (yenI) was isolated from Y. enterocolitica and demonstrated to direct the synthesis of both HHL and OHHL. DNA sequence analysis revealed an open reading frame (ORF) of 642 bp encoding a protein (YenI) of 24.6 kDa with approximately 20% identity to the LuxI family of proteins. Northern blot analysis of yenI expression indicated yenI is transcribed as a single gene and 5' transcript mapping of yenI identified a transcriptional start site 89 bp upstream of the ORF. DNA sequence analysis of the region downstream of yenI located a second ORF, termed yenR, with significant homology to the LuxR family of transcriptional activators. An insertion mutation of yenI abolishes HHL and OHHL production, indicating its central role in N-acylhomoserine lactone synthesis in Y. enterocolitica. Transcriptional analysis using a chromosomal yenI::luxAB fusion has demonstrated that yenI is not subject to autoinduction but is expressed constitutively. Whilst production of the Yop proteins in the wild type and in yenI mutants is indistinguishable, two-dimensional SDS-PAGE analysis of total cell proteins indicated that a number of proteins lack the yenI mutant.

4-Butyrolactone↗
PubMed2003

Molecular characterization and quantitative analysis of superoxide dismutases in virulent and avirulent strains of Aeromonas salmonicida subsp. salmonicida.

Aeromonas salmonicida subsp. salmonicida is a facultatively intracellular gram-negative bacterium that is the etiological agent of furunculosis, a bacterial septicemia of salmonids that causes significant economic loss to the salmon farming industry. The mechanisms by which A. salmonicida evades intracellular killing may be relevant in understanding virulence and the eventual design of appropriate treatment strategies for furunculosis. We have identified two open reading frames (ORFs) and related upstream sequences that code for two putative superoxide dismutases (SODs), sodA and sodB. The sodA gene encoded a protein of 204 amino acids with a molecular mass of approximately 23.0 kDa (SodA) that had high similarity to other prokaryotic Mn-SODs. The sodB gene encoded a protein of 194 amino acids with a molecular mass of approximately 22.3 kDa that had high similarity to other prokaryotic Fe-SODs. Two enzymes with activities consistent with both these ORFs were identified by inhibition of O(2)(-)-catalyzed tetrazolium salt reduction in both gels and microtiter plate assays. The two enzymes differed in their expression patterns in in vivo- and in vitro-cultured bacteria. The regulatory sequences upstream of putative sodA were consistent with these differences. We could not identify other SOD isozymes such as sodC either functionally or through data mining. Levels of SOD were significantly higher in virulent than in avirulent strains of A. salmonicida subsp. salmonicida strain A449 when cultured in vitro and in vivo.

Aeromonas↗
PubMed2001

Nucleotide sequence of a Dianthovirus RNA1-like RNA found in grassy stunt-diseased rice plants.

A Dianthovirus RNA1-like RNA (DR1L RNA, 4486 nucleotides in length) was found in grassy stunt-diseased rice plants together with Rice grassy stunt virus (RGSV). DR1L RNA has characteristics common to Dianthovirus RNA1 such as (1) presence of a GGAUUUUUAG potential shifty-heptanucleotide at the end of the 5'-proximal ORF, which encodes a 35-kDa protein, followed by a 77-nucleotide sequence capable of forming a stem-loop structure for an efficient--1 frameshift to express the downstream region in a 96-kDa putative replicase protein, (2) presence of nearly identical 17-nucleotide sequences in the 5'-terminal region and in a region upstream of an ORF encoding a 28-kDa, putative capsid protein (CP), and (3) near identity of the 3'-terminal 20 nucleotides to those of Dianthovirus RNAs. Western blot analysis using an antiserum against the C-terminal domain of the putative CP and RT-PCR analysis using primers specific to DR1L RNA of fractions after sucrose density gradient centrifugation of RGSV nucleoproteins indicated that DR1L RNA is associated with the 28-kDa putative CP but not with the 36-kDa RGSV CP. Two additional ORFs for 15-kDa and 33-kDa proteins were present in DR1L RNA although their expression in plants and functions are not known.

Amino Acid Sequence↗
PubMed1999

The vaccinia virus A4OR gene product is a nonstructural, type II membrane glycoprotein that is expressed at the cell surface.

Gene A40R from vaccinia virus (VV) strain Western Reserve has been characterized. The open reading frame (ORF) was predicted to encode a 159 amino acid, 18152 Da protein with amino acid similarity to C-type animal lectins and to the VV A34R protein, a component of extracellular enveloped virus (EEV). Northern blotting and S1 nuclease mapping showed that gene A40R is transcribed early during infection from a position 12 nucleotides upstream of the ORF, producing a transcript of approximately 600 nucleotides. Rabbit anti-sera were raised against bacterial fusion proteins containing parts of the A40R protein. These were used to identify an 18 kDa primary translation product and N- and O-glycosylated forms of 28, 35 and 38 kDa. The A40R proteins were detected early during infection, formed higher molecular mass complexes under non-reducing conditions and were present on the cell surface but absent from virions. The proteins partitioned with integral membrane proteins in Triton X-114. Canine pancreatic microsomal membranes protected in vitro-translated A40R from proteinase K digestion, suggesting the A40R protein has type II membrane topology. A mutant virus with the A40R gene disrupted after amino acid 50, so as to remove the entire lectin-like domain, and a revertant virus were constructed. Disruption of the A40R gene did not affect virus plaque size, in vitro growth rate and titre, EEV formation, or virus virulence in a murine intranasal model.

Administration, Intranasal↗
PubMed2001

Expression kinetics of the transcript and product of the UL28 homologue of bovine herpesvirus 1.

We report that the bovine herpesvirus 1 (BHV1) UL28 ORF, a homologue of the herpes simplex virus (HSV) UL28 gene, represents a functional gene encoding a viral specific protein. The BHV1 UL28 ORF, located at positions 53058-->55538 of the viral genome, encodes a viral specific transcript of 3.4 kb detected at 6 h post-infection (p.i.) after which its levels accumulated up to 12 h p.i. and then remained constant up to 24 h p.i. Transcription of the BHV1 UL28 was determined to initiate 95 bases upstream from the ORF's initiating codon, which corresponds to 33 nucleotides downstream from a putative TATA box. A BHV1 UL28 specific antiserum, generated against a T7-Tag/UL28 fusion protein expressed in E. coli, specifically reacted with a 100 kDa protein in Western blots of BHV1-infected protein cell lysates. The expression kinetics of the protein was delayed by 6 h relative to that of its transcript suggesting that the gene is regulated at the translational level. In contrast to the HSV and pseudorabies virus UL28 genes, which belong to viral genes of the early (beta) class, that of BHV1 was unambiguously classified as a gamma2 gene. Further studies will be required to determine whether these kinetic differences have any functional implications.

5' Untranslated Regions↗
PubMed1992

Steroid hormone synthesis by a vaccinia enzyme: a new type of virus virulence factor.

Vaccinia virus open reading frame (ORF) SalF7L has 31% amino acid identity to human 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD). Here we show that SalF7L encodes an active 3 beta-HSD, by the conversion of pregnenolone to the steroid hormone progesterone. The gene is transcribed early during infection into a 1.4 kb mRNA from an initiation site 12 bp upstream of the ORF. An antiserum raised against bacterially expressed SalF7L immunoprecipitated a 38 kDa polypeptide from infected cells, but not from mock infected cells or from cells infected with a mutant virus from which the SalF7L ORF had been removed. Deletion of the gene had no effect on virus replication in CV-1 cells in culture, yet the deletion mutant was attenuated when intranasally inoculated into mice. This steroid hormone synthesizing enzyme is a novel type of virus virulence factor.

3-Hydroxysteroid Dehydrogenases↗
PubMed2002

Transcriptional analysis and preliminary characterization of ORF Bm42 from Bombyx mori nucleopolyhedrovirus.

Clusters of closely spaced genes are frequently present in baculovirus genomes. We report here the detailed transcriptional mapping of one such gene cluster from Bombyx mori nucleopolyhedrovirus (BmNPV) comprising five ORFs, viz., Bm42, Lef-10, VP1054, Bm44, and Bm45, which are closely spaced and transcribed in the same orientation. This region is homologous to ORFs 53, 53a, 54, 55, and 56, respectively, on the AcMNPV genome. Multiple, overlapping sets of polycistronic transcripts from this region, that initiate independently but terminate at a common 3' end, were detected following BmNPV infection. Expression of these genes followed a temporal pattern where the shorter transcripts initiating downstream appeared early, and with the progress of infection the longer transcripts initiated from upstream. The first ORF in this cluster, Bm42, is conserved in almost all baculoviruses, but has not been characterized so far. The protein was localized in the cytosol, predominantly near the nucleus-cytoplasm boundary in BmNPV-infected BmN cells. Bm42 was present in the budded virions and was not associated with occluded virus particles or the polyhedral matrix.

Animals↗
PubMed2006

Sequence and organization of pMAC, an Acinetobacter baumannii plasmid harboring genes involved in organic peroxide resistance.

Acinetobacter baumannii 19606 harbors pMAC, a 9540-bp plasmid that contains 11 predicted open-reading frames (ORFs). Cloning and transformation experiments using Acinetobacter calcoaceticus BD413 mapped replication functions within a region containing four 21-bp direct repeats (ori) and ORF 1, which codes for a predicted replication protein. Subcloning and tri-parental mating experiments mapped mobilization functions to the product of ORF 11 and an adjacent predicted oriT. Three ORFs code for proteins that share similarity to hypothetical proteins encoded by plasmid genes found in other bacteria, while the predicted products of three others do not match any known sequence. The product of ORF 8 is similar to Ohr, a hydroperoxide reductase responsible for organic peroxide detoxification and resistance in bacteria. This ORF is immediately upstream of a coding region whose product is related to the MarR family of transcriptional regulators. Disk diffusion assays showed that A. baumannii 19606 is resistant to the organic peroxide-generating compounds cumene hydroperoxide (CHP) and tert-butyl hydroperoxide (t-BHP), although to levels lower than those detected in Pseudomonas aeruginosa PAO1. Cloning and introduction of the ohr and marR ORFs into Escherichia coli was associated with an increase in resistance to CHP and t-BHP. This appears to be the first case in which the genetic determinants involved in organic peroxide resistance are located in an extrachromosomal element, a situation that can facilitate the horizontal transfer of genetic elements coding for a function that protects bacterial cells from oxidative damage.

Acinetobacter baumannii↗
PubMed1991

Upstream gene of the mgl operon controls the level of MglA protein in Myxococcus xanthus.

The mgl operon contains two open reading frames (ORFs) which are transcribed together. A collection of nonmotile mutants helped to define the downstream ORF as the mglA gene. Single mutations at the mglA locus completely abolish motility. A series of deletion mutations was constructed to determine the role of the upstream ORF (now called mglB). A strain carrying a deletion in mglB and with an intact mglA produces small colonies. The cells are motile, but their rate of swarm spreading is reduced. Measurements of cell movement showed that mglB mutant cells advanced, on average, less than 0.1 cell length in 5 min. The mglB+ cells advanced an average of 1.3 cell lengths in the same time. Extracts of delta mglB cells contain 15 to 20% as much of the 22-kDa MglA protein as do mglB+ cells, as measured in Western immunoblots and enzyme-linked immunosorbent assays. However, the amount of mgl transcript is the same in the delta mglB mutants as in the mglB+ strain. Heterozygous partial diploids mglB/mglA with the wild-type alleles in trans have normal motility, demonstrating that the largest of the mglB deletions is not polar on mglA. Like other motility defects, a delta mglB mutation alters fruiting body development and sporulation. The mglB mutants delayed aggregation, produced small immature fruiting bodies, and sporulated at 45 to 50% wild-type levels. All aspects of the mglB mutant phenotype are explained by the reduced levels of mglA protein and the assumption that it limits the amount of gliding.

Bacterial Proteins↗
PubMed1992

Identification of sbcD mutations as cosuppressors of recBC that allow propagation of DNA palindromes in Escherichia coli K-12.

The function of an open reading frame (orf-45) located upstream of the sbcC gene of Escherichia coli was investigated. Mutations that inactivate sbcC improve the ability to propagate lambda red gam phage that carry a palindromic sequence in their DNA. They also act with sbcB mutations as cosuppressors of the defects in recombination, DNA repair, and cell viability associated with recBC mutations. A 1,282-bp cassette encoding resistance to kanamycin was used to disrupt orf-45. The mutation, which has a polar effect on the expression of sbcC, allowed stable propagation of palindromic lambda phage even when the sbcC gene product was provided in trans. Additional nonpolar mutations in orf-45 were isolated on the basis of their ability to improve the growth of recBC sbcB strains. These mutations also confer resistance to mitomycin C, allow efficient recombination in Hfr crosses, and facilitate stable propagation of palindromic phage. It is concluded that the products of orf-45 and sbcC are functionally related. The orf-45 gene is therefore renamed sbcD.

Bacteriophage lambda↗
PubMed2006

Sequence, organization, transcription and regulation of lactose and galactose operons in Lactobacillus rhamnosus TCELL-1.

AIMS: Understanding the metabolism of lactose and galactose and their regulation in Lactobacillus rhamnosus. METHODS AND RESULTS: A gene cluster containing nine open reading frames (ORFs) involved in the metabolism of lactose and galactose in Lact. rhamnosus TCELL-1 was sequenced and characterized. The order of the ORFs was lacTEGF and galKETRM. Northern blotting experiments revealed that the gene cluster could be transcribed as one lacTEGF-galKETRM mRNA though three major transcripts (lacTEGF, galKETRM and galETRM) were detected for the gene cluster. The transcription of the lac or gal operon was independently induced in the presence of lactose or galactose. Northern blotting and primer extension experiments found the presence of four putative promoters upstream from the ORFs lacT (lacTp), galK (galKp1 and galKp2) and galE (galEp). The measurements of enzymatic activities of GalK, GalE and GalT suggested that the expression of the gal operon was subjected to a galactose activation and glucose repression mechanism. CONCLUSIONS: In Lact. rhamnosus TCELL-1, the galactose moiety of lactose could be metabolized by two alternative pathways (the Leloir and the tagatose 6-phosphate pathways) whereas galactose metabolism could be mediated by the Leloir pathway. SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides important information about sugar metabolism in Lact. rhamnosus.

Amino Acid Sequence↗
PubMed2001

Structure and expression of the TREX1 and TREX2 3' --> 5' exonuclease genes.

The TREX1 and TREX2 genes encode mammalian 3'-->5' exonucleases. Expression of the TREX genes in human cells was investigated using a reverse transcription-polymerase chain reaction strategy. Our results show that TREX1 and TREX2 are expressed in all tissues tested, providing direct evidence for the expression of these genes in human cells. Potential transcription start sites are identified for the TREX genes using rapid amplification of cDNA ends to recover the 5'-flanking regions of the TREX transcripts. The 5'-flanking sequences indicate transcription initiation from consensus putative promoters identified -140 and -650 base pairs upstream of the TREX1 open reading frame (ORF) and -623 and -753 base pairs upstream of the TREX2 ORF. Novel TREX1 and TREX2 cDNAs are identified that contain protein-coding sequences generated from exons positioned in genomic DNA up to 18 kilobases 5' to the TREX1 ORF and up to 25 kilobases 5' to the TREX2 ORF. These novel cDNAs and sequences in the GenBank data base indicate that transcripts containing the TREX1 and TREX2 ORFs are produced using a variety of mechanisms that include alternate promoter usage, alternative splicing, and varied sites for 3' cleavage and polyadenylation. These initial studies have revealed previously unrecognized complexities in the structure and expression of the TREX1 and TREX2 genes.

Amino Acid Sequence↗
PubMed2005

Detection of low-level promoter activity within open reading frame sequences of Escherichia coli.

The search for promoters has largely been confined to sequences upstream of open reading frames (ORFs) or stable RNA genes. Here we used a cloning approach to discover other potential promoters in Escherichia coli. Chromosomal fragments of approximately 160 bp were fused to a promoterless lacZ reporter gene on a multi-copy plasmid. Eight clones were deliberately selected for high activity and 105 clones were selected at random. All eight of the high-activity clones carried promoters that were located upstream of an ORF. Among the randomly-selected clones, 56 had significantly elevated activity. Of these, 7 had inserts which also mapped upstream of an ORF, while 49 mapped within or downstream of ORFs. Surprisingly, the eight promoters selected for high activity matched the canonical sigma70 -35 and -10 sequences no better than sequences from the randomly-selected clones. For six of the nine most active sequences with orientations opposite to that of the ORF, chromosomal expression was detected by RT-PCR, but defined transcripts were not detected by northern analysis. Our results indicate that the E.coli chromosome carries numerous -35 and -10 sequences with weak promoter activity but that most are not productively expressed because other features needed to enhance promoter activity and transcript stability are absent.

Base Sequence↗