scholarly journals GAA Trinucleotide Repeat Region Regulates M9/pMGA Gene Expression in Mycoplasma gallisepticum

2000 ◽  
Vol 68 (2) ◽  
pp. 871-876 ◽  
Author(s):  
Li Liu ◽  
Kevin Dybvig ◽  
Victor S. Panangala ◽  
Vicky L. van Santen ◽  
Christopher T. French
Keyword(s):  
Gene Expression ◽  
Trinucleotide Repeat ◽  
Mycoplasma Gallisepticum ◽  
Avian Host ◽  
Phase Variable ◽  
Repeat Region ◽  
Chromosomal Dna ◽  
Promoter Regions ◽  
Variable Expression ◽  
Gaa Repeats

ABSTRACT Mycoplasma gallisepticum, the cause of chronic respiratory infections in the avian host, possesses a family of M9/pMGA genes encoding an adhesin(s) associated with hemagglutination. Nucleotide sequences of M9/pMGA gene family members indicate extensive sequence similarity in the promoter regions of both the transcribed and silent genes. The mechanism that regulates M9/pMGA gene expression is unknown, but studies have revealed an apparent correlation between gene expression and the number of tandem GAA repeat motifs located upstream of the putative promoter. In this study, transposon Tn4001was used as a vector with the Escherichia coli lacZ gene as the reporter system to examine the role of the GAA repeats in M9/pMGA gene expression in M. gallisepticum. A 336-bp M9 gene fragment (containing the GAA repeat region, the promoter, and the translation start codon) was amplified by PCR, ligated with alacZ gene from E. coli, and inserted into the Tn4001-containing plasmid pISM2062. This construct was transformed into M. gallisepticum PG31. Transformants were filter cloned on agar supplemented with 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside (X-Gal) to monitor lacZ gene expression on the basis of blue/white color selection. Several cycles of filter cloning resulted in cell lineages in which lacZ gene expression alternated between the On and Off states in successive generations of progeny clones. The promoter regions of the M9-lacZ hybrid genes of individual progeny clones were amplified by PCR and sequenced. The only differences between the promoter regions of the blue and white colonies were in the number of GAA repeats. Clones that expressedlacZ had exactly 12 tandem copies of the GAA repeat. Clones that did not express lacZ invariably had either more than 12 (14 to 16) or fewer than 12 (5 to 11) GAA repeats. Southern analysis of M. gallisepticum chromosomal DNA confirmed that the phase-variable expression of the lacZ reporter gene was not caused by Tn4001 transposition. These data strongly indicate that changes in the length of the GAA repeat region are responsible for regulating M9/pMGA gene expression.

scholarly journals Trinucleotide GAA Repeats Dictate pMGA Gene Expression in Mycoplasma gallisepticum by Affecting Spacing between Flanking Regions

2002 ◽  
Vol 184 (5) ◽  
pp. 1335-1339 ◽  
Author(s):  
Li Liu ◽  
Victor S. Panangala ◽  
Kevin Dybvig
Keyword(s):  
Gene Expression ◽  
Gene Regulation ◽  
Promoter Region ◽  
Phase Variation ◽  
Mycoplasma Gallisepticum ◽  
Respiratory Pathogen ◽  
Repeat Region ◽  
Repeat Units ◽  
Gaa Repeats ◽  
Successive Generations

ABSTRACT The pMGA genes of the avian respiratory pathogen Mycoplasma gallisepticum encode a family of hemagglutinins that are subject to phase variation. A trinucleotide GAA repeat region is located upstream of the pMGA transcription start site. The length of the repeat region varies at a high frequency due to changes in the number of repeat units. Previous studies have shown that pMGA genes are transcribed when 12 GAA repeats are present but are not transcribed when the number of repeats is not 12. To further analyze the mechanism of gene regulation, the pMGA promoter region was modified either by deleting the nucleotides 5" of the GAA repeats or by inserting linkers of 10 or 12 bp at a position 3" of the repeats. The modified promoter region was fused to a promoterless lacZ gene and transformed into M. gallisepticum by using transposon Tn4001 as a vector. Transformants and successive generations of progeny were analyzed with 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside (X-Gal) to monitor β-galactosidase activity. For the transformants of M. gallisepticum containing the reporter with deletion of nucleotides 5" of the GAA repeats, GAA-dependent pMGA gene regulation was abolished. For the transformants containing the reporter with an addition of 10- or 12-bp linkers, lacZ was expressed only when eight GAA repeats were present. These data indicate that the nucleotides 5" of the GAA repeats as well as the spacing between the GAA repeats and sequences downstream (3") of the repeats are important for pMGA gene expression.

scholarly journals Local and Global Regulators Linking Anaerobiosis to cupA Fimbrial Gene Expression in Pseudomonas aeruginosa

2007 ◽  
Vol 189 (23) ◽  
pp. 8667-8676 ◽  
Author(s):  
Isabelle Vallet-Gely ◽  
Josh S. Sharp ◽  
Simon L. Dove
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Opportunistic Pathogen ◽  
Phase Variable ◽  
Global Regulators ◽  
Variable Expression ◽  
Regulatory Cascade ◽  
Abiotic Surfaces ◽  
Positive Regulators ◽  
Anaerobic Environment

ABSTRACT The cupA gene cluster of Pseudomonas aeruginosa encodes components and assembly factors of a putative fimbrial structure that enable this opportunistic pathogen to form biofilms on abiotic surfaces. In P. aeruginosa the control of cupA gene expression is complex, with the H-NS-like MvaT protein functioning to repress phase-variable (on/off) expression of the operon. Here we identify four positive regulators of cupA gene expression, including three unusual regulators encoded by the cgrABC genes and Anr, a global regulator of anaerobic gene expression. We show that the cupA genes are expressed in a phase-variable manner under anaerobic conditions and that the cgr genes are essential for this expression. We show further that cgr gene expression is negatively controlled by MvaT and positively controlled by Anr and anaerobiosis. Expression of the cupA genes therefore appears to involve a regulatory cascade in which anaerobiosis, signaled through Anr, stimulates expression of the cgr genes, resulting in a concomitant increase in cupA gene expression. Our findings thus provide mechanistic insight into the regulation of cupA gene expression and identify anaerobiosis as an inducer of phase-variable cupA gene expression, raising the possibility that phase-variable expression of fimbrial genes important for biofilm formation may occur in P. aeruginosa persisting in the largely anaerobic environment of the cystic fibrosis host lung.

scholarly journals The CgrA and CgrC Proteins Form a Complex That Positively RegulatescupAFimbrial Gene Expression in Pseudomonas aeruginosa

2011 ◽  
Vol 193 (22) ◽  
pp. 6152-6161 ◽  
Author(s):  
Heather R. McManus ◽  
Simon L. Dove
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Mutant Strain ◽  
Protein Interaction ◽  
Phase Variable ◽  
Content Type ◽  
Variable Expression ◽  
Transcription Regulator ◽  
Protein Protein Interaction ◽  
Regulatory Effects

The CgrA and CgrC proteins ofPseudomonas aeruginosaare coregulators that are required for the phase-variable expression of thecupAfimbrial genes. Neither CgrA nor CgrC resembles a classical transcription regulator, and precisely how these proteins exert their regulatory effects oncupAgene expression is poorly understood. Here, we show that CgrA and CgrC interact with one another directly. We identify a mutant of CgrC that is specifically defective for interaction with CgrA and demonstrate that this mutant cannot restore the phase-variable expression of thecupAfimbrial genes to cells of acgrCmutant strain. Using this mutant, we also show that CgrC associates with thecupApromoter regardless of whether or not it interacts with CgrA. Our findings establish that interaction between CgrA and CgrC is required for the phase-variable expression of thecupAfimbrial genes and suggest that CgrC exerts its regulatory effects directly at thecupApromoter, possibly by recruiting CgrA. Because the regions of CgrA and CgrC that we have identified as interacting with one another are highly conserved among orthologs, our findings raise the possibility that CgrA- and CgrC-related regulators present in other bacteria function coordinately through a direct protein-protein interaction.

scholarly journals Global Changes in Mycoplasma gallisepticum Phase-Variable Lipoprotein GenevlhAExpression duringIn VivoInfection of the Natural Chicken Host

2015 ◽  
Vol 84 (1) ◽  
pp. 351-355 ◽  
Author(s):  
K. Pflaum ◽  
E. R. Tulman ◽  
J. Beaudet ◽  
X. Liao ◽  
S. J. Geary
Keyword(s):  
Gene Expression ◽  
Phase Variation ◽  
Mycoplasma Gallisepticum ◽  
Chronic Respiratory Disease ◽  
Etiologic Agent ◽  
Economic Losses ◽  
Global Changes ◽  
Phase Variable ◽  
Content Type ◽  
Host Interaction

Mycoplasma gallisepticumis the primary etiologic agent of chronic respiratory disease in poultry, a disease largely affecting the respiratory tract and causing significant economic losses worldwide. Immunodominant proteins encoded by members of the variable lipoprotein and hemagglutinin (vlhA) gene family are thought to be important for mechanisms ofM. gallisepticum-host interaction, pathogenesis, and immune evasion, but their exact role and the overall nature of their phase variation are unknown. To better understand these mechanisms, we assessed global transcriptomicvlhAgene expression directly fromM. gallisepticumpopulations present on tracheal mucosae during a 7-day experimental infection in the natural chicken host. Here we report differences in both dominant and minorvlhAgene expression levels throughout the first week of infection and starting as early as day 1 postinfection, consistent with a functional role not dependent on adaptive immunity for driving phase variation. Notably, data indicated that, at given time points, specificvlhAgenes were similarly dominant in multiple independent hosts, suggesting a nonstochastic temporal progression of dominantvlhAgene expression in the colonizing bacterial population. The dominant expression of a givenvlhAgene was not dependent on the presence of 12-copy GAA trinucleotide repeats in the promoter region and did not revert to the predominatevlhAgene when no longer faced with host pressures. Overall, these data indicate thatvlhAphase variation is dynamic throughout the earliest stages of infection and that the pattern of dominantvlhAexpression may be nonrandom and regulated by previously unrecognized mechanisms.

scholarly journals Expression of the pMGA Genes of Mycoplasma gallisepticum Is Controlled by Variation in the GAA Trinucleotide Repeat Lengths within the 5′ Noncoding Regions

1998 ◽  
Vol 66 (12) ◽  
pp. 5833-5841 ◽  
Author(s):  
Michelle D. Glew ◽  
Nina Baseggio ◽  
Philip F. Markham ◽  
Glenn F. Browning ◽  
Ian D. Walker
Keyword(s):  
Gene Expression ◽  
Sequence Analysis ◽  
In Vitro Culture ◽  
Expression Pattern ◽  
Trinucleotide Repeat ◽  
Mycoplasma Gallisepticum ◽  
Normal Strain ◽  
Specific Antibodies ◽  
Noncoding Regions

ABSTRACT We analyzed the segment of DNA which contains the expressed pMGA gene from one strain of Mycoplasma gallisepticum in normal (strain S6) cells and in cells in which pMGA1.1 gene expression had ceased as a consequence of in vitro culture in the presence of pMGA1.1-specific antibodies. Sequence analysis of isolates lacking pMGA1.1 expression revealed that this gene, which is typically expressed, exhibited sequence changes within a region 5′ to its promoter. Specifically, pMGA1.1+ cells contained a (GAA)12 motif upstream of the promoter, whereas in pMGA1.1− cells the corresponding region contained a (GAA)10 motif; when such cells were grown in medium no longer containing pMGA-specific antibodies, pMGA1.1 was reexpressed and the 5′ (GAA)12 motif was restored. Two other genes, pMGA1.9 and pMGA1.2, were also shown to acquire a (GAA)12 motif in clones which expressed these genes. The results imply the evolution by the pMGA genes of M. gallisepticum of a novel transcriptional requirement which facilitates rapid and reversible switches in the pMGA expression pattern.

scholarly journals Role of CCAA Nucleotide Repeats in Regulation of Hemoglobin and Hemoglobin-Haptoglobin Binding Protein Genes ofHaemophilus influenzae

1999 ◽  
Vol 181 (18) ◽  
pp. 5865-5870 ◽  
Author(s):  
Zhen Ren ◽  
Hongfan Jin ◽  
Paul W. Whitby ◽  
Daniel J. Morton ◽  
Terrence L. Stull
Keyword(s):  
Haemophilus Influenzae ◽  
Gene Fusion ◽  
Binding Protein ◽  
Phase Variable ◽  
Repeat Region ◽  
Variable Expression ◽  
Ofhaemophilus Influenzae ◽  
Nucleotide Repeats

ABSTRACT Haemophilus influenzae utilizes hemoglobin and hemoglobin-haptoglobin as heme sources. The H. influenzaehemoglobin- and hemoglobin-haptoglobin binding protein genes,hgpA, hgpB, and hgpC, contain lengths of tetrameric CCAA repeats. Using an hgpA-lacZtranslational gene fusion, we demonstrate phase-variable expression oflacZ associated with alteration in the length of the CCAA repeat region.

scholarly journals RNA Sequencing of Human Peripheral Blood Cells Indicates Upregulation of Immune-Related Genes in Huntington's Disease

2020 ◽  
Vol 11 ◽  
Author(s):  
Miguel A. Andrade-Navarro ◽  
Katja Mühlenberg ◽  
Eike J. Spruth ◽  
Nancy Mah ◽  
Adrián González-López ◽  
...  
Keyword(s):  
Gene Expression ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Peripheral Blood ◽  
Blood Cells ◽  
Trinucleotide Repeat ◽  
Neurodegenerative Disorder ◽  
Gene Expression Signature ◽  
Interferon Response ◽  
Peripheral Blood Cells

Huntington's disease (HD) is an autosomal dominantly inherited neurodegenerative disorder caused by a trinucleotide repeat expansion in the Huntingtin gene. As disease-modifying therapies for HD are being developed, peripheral blood cells may be used to indicate disease progression and to monitor treatment response. In order to investigate whether gene expression changes can be found in the blood of individuals with HD that distinguish them from healthy controls, we performed transcriptome analysis by next-generation sequencing (RNA-seq). We detected a gene expression signature consistent with dysregulation of immune-related functions and inflammatory response in peripheral blood from HD cases vs. controls, including induction of the interferon response genes, IFITM3, IFI6 and IRF7. Our results suggest that it is possible to detect gene expression changes in blood samples from individuals with HD, which may reflect the immune pathology associated with the disease.

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