Biomedical subjects

D X Zhou

Publications and source records attributed to D X Zhou.

At least 19 recordsLinked to original sources

PubMed2003

A jasmonate-responsive element within the A. thaliana vsp1 promoter.

The vsp1 gene of Arabidopsis thaliana encodes a storage protein that accumulates in vegetative organs. Transgenic plants expressing a vsp1 promoter-gus (beta-glucuronidase) gene fusion were found to contain high GUS activity when challenged with jasmonate, a volatile plant hormone. The induction of vsp1-gus expression by jasmonate could be measured in tobacco mesophyll protoplasts, after transient expression. A number of deletions were operated in the vsp1 promoter in order to locate its jasmonate-responsive element. A 41 bp sequence taken approximately 150 bp upstream of the vsp1 TATA box could confer jasmonate responsiveness upon a short CaMV 35S promoter. Whereas the deletion of a CAAT box-like element within the 41 bp sequence did not affect promoter activity, mutation of a short palindromic motif completely abolished jasmonate responsiveness. This motif shows no homology with the jasmonate-responsive elements of other promoters.

Arabidopsis↗

PubMed2001

Ectopic expression of TATA box-binding protein induces shoot proliferation in Arabidopsis.

The TATA box-binding protein (TBP) is an essential component of transcription initiation complexes of all three eukaryotic RNA polymerases. Increasing evidence suggests that the TBP activity and availability may be regulated to precisely control gene transcription and play an important role in cell type-specific regulation. Arabidopsis TBP-2 is up-regulated in apical shoot tissues. Overexpression of TBP-2 in transgenic Arabidopsis induces apical shoot proliferation. The expression of some shoot meristem regulatory genes is altered. These data suggest that the TBP gene dosage and/or expression level may play an important role in controlling shoot production and plant morphology.

Arabidopsis↗

PubMed1999

Characterization and functional analysis of Arabidopsis TFIIA reveal that the evolutionarily unconserved region of the large subunit has a transcription activation domain.

TFIIA has initially been identified as a component of transcription initiation complex of RNA polymerase II. Its role in transcription has been controversial. In this paper, we report the characterization and functional analysis of both the Arabidopsis TFIIA large and small subunits. Sequence analysis revealed that Arabidopsis TFIIA is structurally more related to animal than to yeast counterparts. Arabidopsis has at least two genes for the large subunit and one for the small subunit. Both types of genes are constitutively transcribed in various plant organs. The proteins encoded by the cDNA interact each other in yeast 2-hybrid system. Only the N-terminal part of the large subunit is necessary for the interaction with the small subunit. Recombinant Arabidopsis TFIIA polypeptides bind to TBP-DNA complex in gel shift assays. The large subunit of TFIIA can stimulate transcription in yeast and in plant cells when fused to a DNA-binding domain binding to cis sequences upstream of a minimal promoter. This trans-activating activity is localized to a 35 amino acid segment within the evolutionarily unconserved central region.

Amino Acid Sequence↗

PubMed1999

Transcriptional activation by Arabidopsis GT-1 may be through interaction with TFIIA-TBP-TATA complex.

GT-1 belongs to the class of trihelix DNA-binding proteins and binds to a promoter sequence found in many different genes. Data presented in this report show that GT-1 contains a trans-activation function in yeast and in plant cells. However, in tobacco BY-2 protoplasts, this activity functions only when an internal region containing the DNA-binding domain is deleted. Gel-shift and co-immunoprecipitation assays have revealed that GT-1 can interact with and stabilize the TFIIA-TBP-TATA complex. These results suggest that GT-1 may activate transcription through direct inter- action with the transcriptional pre-initiation complex.

Arabidopsis↗

PubMed1998

COP1b, an isoform of COP1 generated by alternative splicing, has a negative effect on COP1 function in regulating light-dependent seedling development in Arabidopsis.

COP1 is a negative regulator of Arabidopsis light-dependent development. Mutation of the COP1 locus causes constitutive photomorphogenesis in the dark. Here, we report the identification of an isoform of the COP1 protein, named COP1b, which is generated by alternative splicing. COP1b has a 60-amino acid deletion in the WD-40 repeat domain relative to the full-length COP1. This splicing step is light-independent and takes place mostly in mature seeds and in germinating seedlings. Transgenic Arabidopsis plants that overexpress COP1b show a de-etiolated phenotype in the dark, with a short hypocotyl, open and developed cotyledons. The transgenic seedlings are adult-lethal. These phenotypes closely resemble that of severe cop-1 mutants, indicating that COP1b has a dominant negative effect on COP1 function.

Amino Acid Sequence↗

PubMed1996

The mechanism of GT element-mediated cell type-specific transcriptional control.

Promoter studies have revealed that sequences related to the GT-1 binding site, known as GT elements, are conserved in plant nuclear genes of diverse functions. In this work, we addressed the issue of whether GT elements are involved in cell type-specific transcriptional regulation. We found that the inactivation of GT-1 site-mediated transcription in roots is correlated with the absence of the GT-1 binding activity in root extracts. In addition, the mutation of the related GT-1 (from the pea rbcs-3A) and the S1F (from the spinach rps1) sites resulted in an increase of their transcriptional activity in roots that contain a distinct GT element-binding factor, referred to as RGTF. Although specific to GT elements, RGTF has a different sequence requirement and a lower sequence specificity than GT-1. Interestingly, RGTF has a higher binding affinity to the mutant GT-1 and S1F sites than to the wild-type sequences. This correlation suggests that RGTF may have some role in transcriptional regulation in roots. Furthermore, root cellular protein extracts contain an inhibitory activity that prevents GT-1 from binding to DNA. This helps to explain the absence of the GT-1 binding activity in roots in which the gene of GT-1 is expressed. Together, these data suggest that the cell type-specific transcription modulation by GT elements is achieved by using two different strategies.

DNA-Binding Proteins↗

PubMed1995

Molecular cloning of a small DNA binding protein with specificity for a tissue-specific negative element within the rps1 promoter.

A cDNA encoding a specific binding activity for the tissue-specific negative cis-element S1F binding site of spinach rps1 was isolated from a spinach cDNA expression library. This cDNA of 0.7 kb encodes an unusual small peptide of only 70 amino acids, with a basic domain which contains a nuclear localization signal and a putative DNA binding helix. This protein, named S1Fa, is highly conserved between dicotyledonous and monocotyledonous plants and may represent a novel class of DNA binding proteins. The corresponding mRNA is accumulated more in roots and in etiolated seedlings than in green leaves. This expression pattern is correlated with the tissue-specific function of the S1F binding site which represses the rps1 promoter preferentially in roots and in etiolated plants.

Amino Acid Sequence↗

PubMed1995

Cis-acting elements and expression pattern of the spinach rps22 gene coding for a plastid-specific ribosomal protein.

In order to study the regulation of nuclear genes coding for plastid ribosomal proteins, we have analysed the promoter region of spinach rps22 using both in vitro and in vivo approaches. By footprinting analyses, we have identified eight DNA elements interacting with spinach leaf nuclear factors in the 300 bp promoter region upstream of the transcription start site. Among these elements, four are short AT-rich sequences and one is identical to the Hex motif characterized initially in wheat histone genes. In transgenic tobacco plants, the reporter gene coding for the beta-glucuronidase (GUS) directed by a 1.2 kb upstream region of rps22 was expressed in several plant organs, with high levels in leaf mesophyll, embryo cotyledons and root meristematic cells and very low levels in other cell types. Interestingly, when deleted to -295, the promoter, which contained all the foot-printed elements, was still able to confer the same expression pattern, although the activity was relatively lower than with the 1.2 kb promoter. When deleted further to -154, the promoter, from which the AT-rich elements were eliminated, loses its activity almost completely, suggesting that these AT-rich elements are important for the rps22 promoter activity. Altogether, our results show that rps22 gene expression is controlled by specific cis elements not present in other nuclear-encoded plastid ribosomal protein genes studied so far.

Base Sequence↗

PubMed1994

S1F binding site is related to but different from the light-responsive GT-1 binding site and differentially represses the spinach rps1 promoter in transgenic tobacco.

Nuclear genes encoding plastid ribosomal proteins are more highly expressed in leaves than in roots. This leaf-specific induction seems to be light-independent. We have previously characterized a spinach nuclear factor S1F binding to a cis-element within the rps1 promoter, which negatively regulates both the rps1 and the cauliflower mosaic virus 35S promoters in transient expression assays. Here, we show that the S1F binding site is related to but different from the light-responsive Box II of the pea rbcS-3A promoter, which is recognized by the nuclear factor GT-1. Transgenic plant analyses showed that the S1F site tissue-specifically represses the rps1 promoter in roots as well as in etiolated seedlings. We suggest that the GT-1-related S1F binding site is responsible, at least in part, for the transcriptional repression of rps1 in nonphotosynthetic tissues such as roots.

Base Sequence↗

PubMed1993

[Investigation of chronic arsenic poisoning caused by high arsenic coal pollution].

This article reports the results of an investigation on environmental arsenic pollution and chronic arsenic poisoning in a rural area. Exploitation of high arsenic coal caused drinking and irrigating water to be polluted by arsenic and burning of this coal caused severe environmental arsenic pollution including air, food, soil and drinking well water. 1548 villagers in 47 villages suffered from chronic arsenic poisoning who used this coal in daily life. The polluted air and food were mainly responsible, while the polluted drinking water and skin absorption played some part in poisoning. When arsenic level in coal is as high as 100mg/kg, we should consider the possibility of environmental arsenic pollution and chronic arsenic poisoning in exposed population. The high arsenic coal's distribution is very uneven. When controlling the disease, it is important to remember monitoring the quantity of arsenic coal outside the arsenic coal mining area.

Arsenic Poisoning↗

PubMed1992

Sequence-specific interaction between S1F, a spinach nuclear factor, and a negative cis-element conserved in plastid-related genes.

The nuclear gene rps1 coding for the spinach plastid ribosomal protein CS1 exhibits both a constitutive and leaf-specific expression pattern. In contrast to other chloroplast-related genes like rbcS and cab, the leaf induction of rps1 expression is light-independent. These unique features of rps1 expression provide good models to study the mechanisms regulating plastid development and differentiation in higher plants. We report on the identification of a spinach leaf nuclear factor, designated S1F, interacting with the rps1 promoter. The S1F binding site is conserved in the promoter region of many plastid-related genes, including rbcS, cab, and rpl21. A binding activity similar to S1F was detected in nuclear extract from dark-grown de-differentiated soybean suspension cells. Through site-specific mutagenesis and transient expression in soybean cell protoplasts, we show that the S1F binding site is a negative element down-regulating the promoter activity of rps1. A ligated tetramer of S1F site was able to repress activity of the cauliflower mosaic virus 35 S promoter extending the negative function of the S1F binding site on promoter activity.

Base Sequence↗

PubMed1992

Structure and expression of the nuclear gene coding for the plastid CS1 ribosomal protein from spinach.

The chloroplast ribosomal protein CS1 is an essential component of the plastids translational machinery involved in translation initiation. Southern analysis suggests that the corresponding nuclear gene is present in one copy in the spinach genome. We have isolated and sequenced the gene (rps1) to study its expression at the transcriptional level. The gene consists of 7 exons and 6 introns including an unusually large intron in the 5' coding region. No canonical TATA-box is found in the 5' upstream region of the gene. rps1 transcripts are detected early during germination and a significant accumulation is observed after the protrusion of the radicle. CS1 mRNAs are present in all organs of young seedlings although there are dramatic differences in the steady state level of the mRNAs between leaves and roots tissues. Transcripts accumulate independently of the presence or absence of light. Band shift analysis shows that the +1, -400 bp region of the gene can bind different sets of proteins isolated from roots and leaves nuclei. We suggest that the expression of the housekeeping plastid-related rps1 gene is regulated in a tissue-specific manner by transcriptional trans-acting factors.

Amino Acid Sequence↗

PubMed1991

The hepatitis B virus S promoter comprises A CCAAT motif and two initiation regions.

The hepatitis B virus S (major surface gene) promoter is embedded in two overlapping open reading frames and specifies several transcripts with heterogeneous 5' termini. We have identified the cis-elements necessary for S promoter function. A single upstream CCAAT element is essential for high level expression in both liver and non-liver cells. No TATA box is present, but two regions surrounding the initiation sites can function separately as initiating elements. These results show that the S promoter has a simple requirement for upstream activating sequences, but a complex initiation region. Therefore, it may provide a suitable model system for studying transcription initiation in non-TATA type promoters.

Base Sequence↗

PubMed1991

The ubiquitous transcription factor Oct-1 and the liver-specific factor HNF-1 are both required to activate transcription of a hepatitis B virus promoter.

The liver-specific transcription factor HNF-1 activates transcription of several mammalian hepatocyte-specific genes. The hepatitis B virus preS1 promoter shows hepatocyte specificity, which has been ascribed to binding of HNF-1 to a cognate DNA sequence upstream of the TATA box. We show here that there is an adjacent site that binds the ubiquitous transcription factor Oct-1. Both the Oct-1 and HNF-1 sites are necessary for liver-specific transcription of the preS1 promoter, but neither site alone activates transcription. The Oct-1 site is also necessary for activation of the preS1 promoter in HeLa cells, expressing transfected HNF-1. Our results show that while Oct-1 is not restricted to hepatocytes, it nevertheless can play a critical role in the expression of a liver-specific gene.

Base Sequence↗

PubMed1990

Differential regulation of the hepatitis B virus surface gene promoters by a second viral enhancer.

The hepatitis B virus surface gene is transcribed from two promoters, and the resulting mRNA species code for three distinct forms of the surface antigen. We show here that the viral transcriptional trans-activator, X protein, has no effect on either promoter. However, a cis-acting element in the downstream half of the X gene, distinct from the previously mapped viral enhancer, selectively activates the major surface gene promoter. Nuclease protection and gel-shift assays reveal that multiple cellular factors bind to two sites within this DNA fragment, both of which are necessary for enhancer activity. Since this region of the viral genome is frequently deleted upon integration into the hsot chromosome in chronic hepatitis B, loss of this second enhancer can alter the relative amounts of the three forms of the surface antigen in infected hepatocytes and thus possibly contribute to cellular damage.

Base Sequence↗

PubMed1990

Activation of class I major histocompatibility complex gene expression by hepatitis B virus.

Normal hepatocytes express very few class I major histocompatibility complex (MHC I) molecules, but MHC I expression is elevated in hepatitis B virus (HBV) infection. We report here that hepatoblastoma cells with replicating HBV genomes express three- to fourfold-higher levels of MHC I protein and mRNA than do parent cells without HBV DNA. Transient transfection assays demonstrated that the HBV X protein trans activated transcription from an MHC I promoter and allowed identification of cis elements important for trans activation.

2',5'-Oligoadenylate Synthetase↗

PubMed1989

Presence in the stroma of chloroplasts of a large pool of a ribosomal protein not structurally related to any Escherichia coli ribosomal protein.

A search was made for the presence of a pool of free ribosomal proteins in the stroma of the spinach chloroplast. The results showed that a relatively large amount of one protein, CS-S5, is present in the stroma. Immunoprecipitation experiments showed that this protein is encoded by the nuclear genome. Clones were isolated from a cDNA library constructed in the expression vector lambda gt11, using specific antibodies raised against the CS-S5 protein. A full-length cDNA was sequenced which contains an open reading frame (ORF) for the precursor of the CS-S5 protein, as shown by immunoprecipitation. This precursor contains a putative transit peptide of 66 amino acids and the mature product has no significant homology with any of the Escherichia coli ribosomal proteins, in contrast to the other ribosomal protein gene products so far identified in spinach chloroplasts.

Amino Acid Sequence↗

PubMed1989

Cotranscription of the S10- and spc-like operons in spinach chloroplasts and identification of three of their gene products.

The organisation and expression of the rpl22, rps3, rpl16 and rpl14 genes, which belong to the S10- and spc-like operons of spinach chloroplasts, have been studied. Northern experiments and nuclease S1 mapping show that the two operon-like groups of genes are cotranscribed. It is demonstrated that the intron-containing rpl16 gene is spliced in vivo. Based on amino acid composition and protein sequence data, the products of the rpl22, rpl16 and rpl14 genes are identified respectively as the spinach chloroplast ribosomal proteins CS-L13, CS-L24 and CS-L29. The rpl22 gene product is a 5S rRNA binding protein and therefore is distinguishable from the homologous Escherichia coli L22 ribosomal protein.

Amino Acid Sequence↗