Use of chromosomal gene fusions to investigate the role of repetitive DNA in regulation of genes involved in lipopolysaccharide biosynthesis in Haemophilus influenzae.

The locus lex2, comprising lex2A and lex2B, contributes to the phase-variable expression of lipopolysaccharide (LPS) of Haemophilus influenzae and was found to be present in 74 % of strains investigated. lex2A contains 5′-GCAA repeats which vary in number from 4 to 46 copies between strains. The locus was cloned from the serotype b strains RM7004 and RM153 and showed >99 % nucleotide sequence identity between these strains and the published lex2 sequence. Disruption of the lex2B gene in strain RM7004 resulted in truncation of some LPS glycoforms, shown by gel fractionation, with only one glycoform reacting with a digalactoside-specific monoclonal antibody, 4C4, compared with four LPS glycoforms in the more elongated LPS of the parent strain. Mass spectrometry and NMR analyses of LPS from the lex2B mutant revealed loss of the terminal digalactoside as well as the second β-glucose extending from the first heptose of the inner core. The authors conclude that Lex2B is the β-(1-4)-glucosyltransferase that adds the second β-glucose to the first β-glucose as part of the oligosaccharide extension from the first heptose of the LPS of strain RM7004. Investigation of the expression of the lex2 locus indicated that the genes are co-transcribed and that both reading frames are required for addition of this second β-glucose in a phase-variable manner.

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DNA methylation in satellite repeats disorders

Essays in Biochemistry ◽

10.1042/ebc20190028 ◽

2019 ◽

Vol 63 (6) ◽

pp. 757-771 ◽

Cited By ~ 4

Author(s):

Claire Francastel ◽

Frédérique Magdinier

Keyword(s):

Dna Methylation ◽

Human Genome ◽

Repetitive Dna ◽

Dna Sequences ◽

Satellite Repeats ◽

Tremendous Progress ◽

Genes Encoding ◽

Dna Elements ◽

Near Future

Abstract Despite the tremendous progress made in recent years in assembling the human genome, tandemly repeated DNA elements remain poorly characterized. These sequences account for the vast majority of methylated sites in the human genome and their methylated state is necessary for this repetitive DNA to function properly and to maintain genome integrity. Furthermore, recent advances highlight the emerging role of these sequences in regulating the functions of the human genome and its variability during evolution, among individuals, or in disease susceptibility. In addition, a number of inherited rare diseases are directly linked to the alteration of some of these repetitive DNA sequences, either through changes in the organization or size of the tandem repeat arrays or through mutations in genes encoding chromatin modifiers involved in the epigenetic regulation of these elements. Although largely overlooked so far in the functional annotation of the human genome, satellite elements play key roles in its architectural and topological organization. This includes functions as boundary elements delimitating functional domains or assembly of repressive nuclear compartments, with local or distal impact on gene expression. Thus, the consideration of satellite repeats organization and their associated epigenetic landmarks, including DNA methylation (DNAme), will become unavoidable in the near future to fully decipher human phenotypes and associated diseases.

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Expression of Individual Copies ofMethylococcus capsulatus Bath Particulate Methane Monooxygenase Genes

Journal of Bacteriology ◽

10.1128/jb.183.5.1810-1812.2001 ◽

2001 ◽

Vol 183 (5) ◽

pp. 1810-1812 ◽

Cited By ~ 33

Author(s):

Sergei Stolyar ◽

Marion Franke ◽

Mary E. Lidstrom

Keyword(s):

Methane Monooxygenase ◽

Gene Clusters ◽

Gene Fusions ◽

Methylococcus Capsulatus ◽

Chromosomal Gene ◽

Particulate Methane Monooxygenase ◽

Relative Expression

ABSTRACT The expression of the two gene clusters encoding the particulate methane monooxygenase (pMMO) in Methylococcus capsulatusBath was assessed by analysis of transcripts and by use of chromosomal gene fusions. The results suggest that the two clusters are functionally redundant but that relative expression alters depending on the copper levels available for growth.

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The htx and ptx Operons of Pseudomonas stutzeri WM88 Are New Members of the Pho Regulon

Journal of Bacteriology ◽

10.1128/jb.186.17.5876-5882.2004 ◽

2004 ◽

Vol 186 (17) ◽

pp. 5876-5882 ◽

Cited By ~ 37

Author(s):

Andrea K. White ◽

William W. Metcalf

Keyword(s):

Reporter Gene ◽

Pseudomonas Stutzeri ◽

Deletion Mutants ◽

Pho Regulon ◽

Gene Fusions ◽

New Members ◽

Starvation Conditions ◽

P Sources

ABSTRACT The htx and ptx operons of Pseudomonas stutzeri WM88 allow for the use of the inorganic reduced phosphorus (P) compounds hypophosphite (P valence, +1) and phosphite (P valence, +3) as sole P sources. To support the proposed in vivo role for the htx and ptx operons, namely the use of phosphite and hypophosphite as alternative P sources, we used reporter gene fusions to examine their expression levels with respect to various P conditions. Expression of the htx and ptx operons was induced up to 17- and 22-fold, respectively, in cultures grown under phosphate starvation conditions relative to expression in medium with excess phosphate (Pi). However, the presence of the reduced P substrate hypophosphite, phosphite, or methylphosphonate, in addition to excess Pi, did not result in an increase in the expression of either operon. To provide further support for a role of the htx and ptx operons in Pi acquisition, we identified P. stutzeri phoBR homologs and constructed deletion mutants. Induction of the htx and ptx reporter gene fusions in response to growth on limiting Pi was abolished in ΔphoB, ΔphoR, and ΔphoBR mutants, demonstrating that htx and ptx expression is phoBR dependent. The putative LysR-type regulator encoded by ptxE has no apparent role in the expression of the htx and ptx operons, as no effect was observed on the level of induction of either operon in a ΔptxE mutant.

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