Search results for "Repetitive sequence"
showing 10 items of 74 documents
Binding of Tat Protein to TAR Region of Human Immunodeficiency Virus Type 1 Blocks TAR-Mediated Activation of (2′-5′)Oligoadenylate Synthetase
1990
The TAR sequence of the 5' leader of HIV-1 long terminal repeat-directed mRNA was found to be able to bind to and to activate double-stranded RNA-dependent (2'-5')A synthetase. Binding of TAR to the purified synthetase in vitro was abolished by addition of HIV-1 Tat protein, which binds to this sequence with a high affinity. Inhibition of TAR-mediated activation of (2'-5')A synthetase by Tat was prevented in the presence of the Zn2+ and Cd2+ chelators o-phenanthroline and penicillamine, which did not impair TAR-synthetase interaction. Transient expression assays of bacterial chloramphenicol acetyltransferase (CAT) gene in HeLa cells revealed that the levels of both CAT mRNA and CAT protein …
Enhancer blocking activity located near the 3′ end of the sea urchin early H2A histone gene
1997
The sea urchin early histone repeating unit contains one copy of each of the five histone genes whose coordinate expression during development is regulated by gene-specific elements. To learn how within the histone repeating unit a gene-specific activator can be prevented to communicate with the heterologous promoters, we searched for domain boundaries by using the enhancer blocking assay. We focused on the region near the 3′ end of the H2A gene where stage-specific nuclease cleavage sites appear upon silencing of the early histone genes. We demonstrated that a DNA fragment of 265 bp in length, defined as sns (for silencing nucleoprotein structure), blocked the enhancer activity of the H2A…
Down-regulation of early sea urchin histone H2A gene relies on cis regulative sequences located in the 5' and 3' regions and including the enhancer b…
2004
The tandem repeated sea urchin alpha-histone genes are developmentally regulated by gene-specific promoter elements. Coordinate transcription of the five genes begins after meiotic maturation of the oocyte, continues through cleavage, and reaches its maximum at morula stage, after which these genes are shut off and maintained in a silenced state for the life cycle of the animal. Although cis regulative sequences affecting the timing and the level of expression of these genes have been characterized, much less is known about the mechanism of their repression. Here we report the results of a functional analysis that allowed the identification of the sequence elements needed for the silencing …
The Physcomitrella genome reveals evolutionary insights into the conquest of land by plants
2008
We report the draft genome sequence of the model moss Physcomitrella patens and compare its features with those of flowering plants, from which it is separated by more than 400 million years, and unicellular aquatic algae. This comparison reveals genomic changes concomitant with the evolutionary movement to land, including a general increase in gene family complexity; loss of genes associated with aquatic environments (e.g., flagellar arms); acquisition of genes for tolerating terrestrial stresses (e.g., variation in temperature and water availability); and the development of the auxin and abscisic acid signaling pathways for coordinating multicellular growth and dehydration response. The …
Comparative sequence analysis of the Clostridium difficile toxins A and B.
1992
The six clones pTB112, pTB324, pTBs12, pCd122, pCd14 and pCd13 cover the tox locus of Clostridium difficile VPI 10463. This region of 19 kb of chromosomal DNA contains four open reading frames including the complete toxB and toxA genes. The two toxins show 63% amino acid (aa) homology, a relatedness that had been predicted by the cross-reactivity of some monoclonal antibodies (mAb) but that is in contrast to the toxin specificity of polyclonal antisera. A special feature of ToxA and ToxB is their repetitive C-termini. We define herein 19 individual CROPs (combined repetitive oligopeptides of 20-50 aa length) in the ToxB C-terminus, which are separable into five homologous groups. Comparison…
Clostridium difficile toxin A carries a C-terminal repetitive structure homologous to the carbohydrate binding region of streptococcal glycosyltransf…
1990
A detailed analysis of the 8130-bp open reading frame (ORF) of gene toxA and of an upstream ORF designated utxA, indicates the presence of a transcription terminator stem-loop for toxA, promoter sequences, and Shine-Dalgarno boxes for toxA and utxA. No transcription terminator between toxA and utxA is suggested by the sequence. ToxA contains two domains, one-third (C-terminal) with a repetitive structure and the residual two-thirds with no repetitions. The 2499-bp sequence encoding the repetitive structure is composed of nine groups of different short repetitive oligodeoxyribonucleotides (SRONs). A combination of these SRONs codes for five groups of combined repetitive oligopeptides (CROPs)…
Characterisation of a Cryptosporidium parvum-specific cDNA clone and detection of parasite DNA in mucosal scrapings of infected mice.
1998
A cDNA library was constructed using total RNA extracted from oocysts and sporozoites of the protozoan parasite Cryptosporidium parvum. The expression library was screened with an anti-C. parvum antiserum and a clone, Cp3.4, with a 2043 bp insert, was extracted. Southern blot analysis demonstrated a single copy gene that was located on a 1.6 Mb chromosome. The gene was found to be C. parvum specific as Cp3.4 did not cross-hybridise with chromosomal DNA from three other apicomplexan parasites. The cDNA encodes a polypeptide with a predicted membrane helix at its C-terminal end which is flanked by stretches of acidic amino acids. Overall, the polypeptide has a low isoelectric point (pI) of 3.…
A novel member of an ancient superfamily: sponge (Geodia cydonium, Porifera) putative protein that features scavenger receptor cysteine-rich repeats
1997
Proteins featuring scavenger receptor cysteine-rich (SRCR) domains are prominent receptors known from vertebrates and from one phylum of invertebrates, the echinoderms. In the present study we report the first putative SRCR protein from the marine sponge Geodia cydonium (Porifera), a member of the lowest phylum of contemporary Metazoans. Two forms of SRCR molecules were characterized, which apparently represent alternative splicing of the same transcript. The long putative SRCR protein, of 1536 aa, features twelve SRCR repeats, a C-terminal transmembrane domain and a cytoplasmic tail. The sequence of the short form is identical with the long form except that it lacks a coding region near th…
Multiple copies of SUC4 regulatory regions may cause partial de-repression of invertase synthesis in Saccharomyces cerevisiae.
1992
Transformation to generate multiple copies of regulatory DNA sequences has been used to study the interactions between regulatory proteins and their target sequences, since a high copy number of these sequences may titrate trans-acting regulatory proteins. We have analyzed the synthesis of invertase in yeast strains carrying different SUC genes transformed with the multiple-copy plasmid pSH143, a derivative of pJDB207 containing the promoter and upstream regulatory sequences of SUC4. The results obtained seem to be strain dependent. Under repressing conditions a high copy number of SUC4 promoter regions may cause increased expression of the invertase genes resulting in the synthesis of exte…
Losing DNA methylation at repetitive elements and breaking bad
2021
Abstract Background DNA methylation is an epigenetic chromatin mark that allows heterochromatin formation and gene silencing. It has a fundamental role in preserving genome stability (including chromosome stability) by controlling both gene expression and chromatin structure. Therefore, the onset of an incorrect pattern of DNA methylation is potentially dangerous for the cells. This is particularly important with respect to repetitive elements, which constitute the third of the human genome. Main body Repetitive sequences are involved in several cell processes, however, due to their intrinsic nature, they can be a source of genome instability. Thus, most repetitive elements are usually meth…