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Characterisation of silent and active genes for a variable large protein of Borrelia recurrentis.

Vidal V, Cutler S, Scragg IG, Wright DJ, Kwiatkowski D - BMC Infect. Dis. (2002)

Bottom Line: This isolate was found to carry silent and expressed copies of the vlp1B. recurrentis A1 gene on plasmids of 54 kbp and 24 kbp respectively, whereas a different isolate, A17, had only the silent vlp1B. recurrentis A17 on a 54 kbp plasmid.Taken together these results suggest that antigenic variation in B. recurrentis may result from recombination of variable large and small protein genes at the junction between lipoprotein leader sequence and mature protein coding region.However, this hypothetical model needs to be validated by further identification of expressed and silent variant protein genes in other B. recurrentis isolates.

View Article: PubMed Central - HTML - PubMed

Affiliation: Molecular Infectious Disease Group, Weatherall Institute of Molecular Medicine, Oxford, UK. vfvidal@yahoo.fr

ABSTRACT

Background: We report the characterisation of the variable large protein (vlp) gene expressed by clinical isolate A1 of Borrelia recurrentis; the agent of the life-threatening disease louse-borne relapsing fever.

Methods: The major vlp protein of this isolate was characterised and a DNA probe created. Use of this together with standard molecular methods was used to determine the location of the vlp1B. recurrentis A1 gene in both this and other isolates.

Results: This isolate was found to carry silent and expressed copies of the vlp1B. recurrentis A1 gene on plasmids of 54 kbp and 24 kbp respectively, whereas a different isolate, A17, had only the silent vlp1B. recurrentis A17 on a 54 kbp plasmid. Silent and expressed vlp1 have identical mature protein coding regions but have different 5' regions, both containing different potential lipoprotein leader sequences. Only one form of vlp1 is transcribed in the A1 isolate of B. recurrentis, yet both 5' upstream sequences of this vlp1 gene possess features of bacterial promoters.

Conclusion: Taken together these results suggest that antigenic variation in B. recurrentis may result from recombination of variable large and small protein genes at the junction between lipoprotein leader sequence and mature protein coding region. However, this hypothetical model needs to be validated by further identification of expressed and silent variant protein genes in other B. recurrentis isolates.

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vlp1B. recurrentis A1 is plasmid encoded and duplicated in isolate A1. A: Plasmid (lane 1 to 4) and chromosome-rich (lane 5 to 8) DNA were digested with EcoRI (lane 1 and 5), HindIII (lane 2 and 6), XbaI (lane 3 and 7), and DraI (lane 4 and 8), transferred to a membrane and hybridised under high stringency with the 715 bp vlp1 probe. B: Plasmid DNA from isolate A1 (lane 1 to 3) and isolate A17 (lanes 4 to 6) and total DNA from isolate A17 (lane 7) were digested with HindIII (lane 1 and 4), EcoRI (lane 2, 5, and 7), XbaI (lane 3 and 6), and treated as described above. C: Intact plasmids from isolate A1 (lane 1) and isolate A17 (lane 2) were separated by field inversion gel electrophoresis (predefined program P1, Biorad) and treated as described above.
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Figure 1: vlp1B. recurrentis A1 is plasmid encoded and duplicated in isolate A1. A: Plasmid (lane 1 to 4) and chromosome-rich (lane 5 to 8) DNA were digested with EcoRI (lane 1 and 5), HindIII (lane 2 and 6), XbaI (lane 3 and 7), and DraI (lane 4 and 8), transferred to a membrane and hybridised under high stringency with the 715 bp vlp1 probe. B: Plasmid DNA from isolate A1 (lane 1 to 3) and isolate A17 (lanes 4 to 6) and total DNA from isolate A17 (lane 7) were digested with HindIII (lane 1 and 4), EcoRI (lane 2, 5, and 7), XbaI (lane 3 and 6), and treated as described above. C: Intact plasmids from isolate A1 (lane 1) and isolate A17 (lane 2) were separated by field inversion gel electrophoresis (predefined program P1, Biorad) and treated as described above.

Mentions: Ungapped DNA sequence alignment of the two forms of vlp1B. recurrentis A1 The upper row represents the sequence derived from the slower migrating 54 kbp plasmid of figure 1C. The sequence corresponding to the UP element consensus found in the bottom row sequence is italicised. The putative '-35' and '-10' elements and ribosome binding sites are underlined. Translation start sites are shown in bold. Region complementary to LLS1 and LLS2 probes are double-underlined. Accession number for both sequences are given in the methods section.


Characterisation of silent and active genes for a variable large protein of Borrelia recurrentis.

Vidal V, Cutler S, Scragg IG, Wright DJ, Kwiatkowski D - BMC Infect. Dis. (2002)

vlp1B. recurrentis A1 is plasmid encoded and duplicated in isolate A1. A: Plasmid (lane 1 to 4) and chromosome-rich (lane 5 to 8) DNA were digested with EcoRI (lane 1 and 5), HindIII (lane 2 and 6), XbaI (lane 3 and 7), and DraI (lane 4 and 8), transferred to a membrane and hybridised under high stringency with the 715 bp vlp1 probe. B: Plasmid DNA from isolate A1 (lane 1 to 3) and isolate A17 (lanes 4 to 6) and total DNA from isolate A17 (lane 7) were digested with HindIII (lane 1 and 4), EcoRI (lane 2, 5, and 7), XbaI (lane 3 and 6), and treated as described above. C: Intact plasmids from isolate A1 (lane 1) and isolate A17 (lane 2) were separated by field inversion gel electrophoresis (predefined program P1, Biorad) and treated as described above.
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Related In: Results  -  Collection

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Figure 1: vlp1B. recurrentis A1 is plasmid encoded and duplicated in isolate A1. A: Plasmid (lane 1 to 4) and chromosome-rich (lane 5 to 8) DNA were digested with EcoRI (lane 1 and 5), HindIII (lane 2 and 6), XbaI (lane 3 and 7), and DraI (lane 4 and 8), transferred to a membrane and hybridised under high stringency with the 715 bp vlp1 probe. B: Plasmid DNA from isolate A1 (lane 1 to 3) and isolate A17 (lanes 4 to 6) and total DNA from isolate A17 (lane 7) were digested with HindIII (lane 1 and 4), EcoRI (lane 2, 5, and 7), XbaI (lane 3 and 6), and treated as described above. C: Intact plasmids from isolate A1 (lane 1) and isolate A17 (lane 2) were separated by field inversion gel electrophoresis (predefined program P1, Biorad) and treated as described above.
Mentions: Ungapped DNA sequence alignment of the two forms of vlp1B. recurrentis A1 The upper row represents the sequence derived from the slower migrating 54 kbp plasmid of figure 1C. The sequence corresponding to the UP element consensus found in the bottom row sequence is italicised. The putative '-35' and '-10' elements and ribosome binding sites are underlined. Translation start sites are shown in bold. Region complementary to LLS1 and LLS2 probes are double-underlined. Accession number for both sequences are given in the methods section.

Bottom Line: This isolate was found to carry silent and expressed copies of the vlp1B. recurrentis A1 gene on plasmids of 54 kbp and 24 kbp respectively, whereas a different isolate, A17, had only the silent vlp1B. recurrentis A17 on a 54 kbp plasmid.Taken together these results suggest that antigenic variation in B. recurrentis may result from recombination of variable large and small protein genes at the junction between lipoprotein leader sequence and mature protein coding region.However, this hypothetical model needs to be validated by further identification of expressed and silent variant protein genes in other B. recurrentis isolates.

View Article: PubMed Central - HTML - PubMed

Affiliation: Molecular Infectious Disease Group, Weatherall Institute of Molecular Medicine, Oxford, UK. vfvidal@yahoo.fr

ABSTRACT

Background: We report the characterisation of the variable large protein (vlp) gene expressed by clinical isolate A1 of Borrelia recurrentis; the agent of the life-threatening disease louse-borne relapsing fever.

Methods: The major vlp protein of this isolate was characterised and a DNA probe created. Use of this together with standard molecular methods was used to determine the location of the vlp1B. recurrentis A1 gene in both this and other isolates.

Results: This isolate was found to carry silent and expressed copies of the vlp1B. recurrentis A1 gene on plasmids of 54 kbp and 24 kbp respectively, whereas a different isolate, A17, had only the silent vlp1B. recurrentis A17 on a 54 kbp plasmid. Silent and expressed vlp1 have identical mature protein coding regions but have different 5' regions, both containing different potential lipoprotein leader sequences. Only one form of vlp1 is transcribed in the A1 isolate of B. recurrentis, yet both 5' upstream sequences of this vlp1 gene possess features of bacterial promoters.

Conclusion: Taken together these results suggest that antigenic variation in B. recurrentis may result from recombination of variable large and small protein genes at the junction between lipoprotein leader sequence and mature protein coding region. However, this hypothetical model needs to be validated by further identification of expressed and silent variant protein genes in other B. recurrentis isolates.

Show MeSH
Related in: MedlinePlus