SB2013 L04gr5: Difference between revisions

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Figure 2 shows the possible dimerization of VlsE.

=Antigenic Variation=

Antigenic variation is the process by which an organism is able to evade its host’s immune system. The antigenic variation that occurs in VlsE uses a complex genetic conversion mechanism that is seen to be concentrated in the VRs. The complex genetic system for VlsE is located near the right telomere on a 28-kb linear plasmid (lp28-1) in strains of ''B. burgdorferi''. This [http://en.wikipedia.org/wiki/Locus_%28genetics%29 locus] has been shown to be a crucial element for the persistence and virulence of Lyme disease (Bankhead and Chaconas ~~2007)~~. The ''vls'' antigenic variation locus consists of a ''vls'' expression site (''vlsE'') and 15 silent vls cassettes that reside just upstream of the site. The ''vlsE'' cassette region, which is the variable domain and does not include the invariable amino or carboxyl termini, has approximately 92% DNA sequence identity with the silent vls cassettes. However, the silent ''vls'' cassettes lack promoter sequences and are therefore not expressed. Throughout the course of infection, the sequences for the flanking termini and the silent ''vls'' cassettes are conserved while the vlsE sequence is recombined. This suggests that the genetic variation mechanism occurs by copying segments of the 15 silent vls cassettes and completely replacing corresponding segments of ''vlsE'' sequences. The resulting differences are centralized in the highly variable regions of the ''vls'' cassettes. This allows for the constant evolution of the VR structures and evades the antibodies of the host immune system.

Antigenic variation is the process by which an organism is able to evade its host’s immune system. The antigenic variation that occurs in VlsE uses a complex genetic conversion mechanism that is seen to be concentrated in the VRs. The complex genetic system for VlsE is located near the right telomere on a 28-kb linear plasmid (lp28-1) in strains of ''B. burgdorferi''. This [http://en.wikipedia.org/wiki/Locus_%28genetics%29 locus] has been shown to be a crucial element for the persistence and virulence of Lyme disease <ref name="Bankhead and Chaconas" />. The ''vls'' antigenic variation locus consists of a ''vls'' expression site (''vlsE'') and 15 silent vls cassettes that reside just upstream of the site. The ''vlsE'' cassette region, which is the variable domain and does not include the invariable amino or carboxyl termini, has approximately 92% DNA sequence identity with the silent vls cassettes. However, the silent ''vls'' cassettes lack promoter sequences and are therefore not expressed. Throughout the course of infection, the sequences for the flanking termini and the silent ''vls'' cassettes are conserved while the vlsE sequence is recombined. This suggests that the genetic variation mechanism occurs by copying segments of the 15 silent vls cassettes and completely replacing corresponding segments of ''vlsE'' sequences. The resulting differences are centralized in the highly variable regions of the ''vls'' cassettes. This allows for the constant evolution of the VR structures and evades the antibodies of the host immune system.

==''Variable Regions''==

SB2013 L04gr5: Difference between revisions

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@@ Line 26: / Line 26: @@
 Figure 2 shows the possible dimerization of VlsE.
 =Antigenic Variation=
-Antigenic variation is the process by which an organism is able to evade its host’s immune system.  The antigenic variation that occurs in VlsE uses a complex genetic conversion mechanism that is seen to be concentrated in the VRs. The complex genetic system for VlsE is located near the right telomere on a 28-kb linear plasmid (lp28-1) in strains of ''B. burgdorferi''.  This [http://en.wikipedia.org/wiki/Locus_%28genetics%29 locus] has been shown to be a crucial element for the persistence and virulence of Lyme disease (Bankhead and Chaconas 2007).  The ''vls'' antigenic variation locus consists of a ''vls'' expression site (''vlsE'') and 15 silent vls cassettes that reside just upstream of the site.  The ''vlsE'' cassette region, which is the variable domain and does not include the invariable amino or carboxyl termini, has approximately 92% DNA sequence identity with the silent vls cassettes.  However, the silent ''vls'' cassettes lack promoter sequences and are therefore not expressed.  Throughout the course of infection, the sequences for the flanking termini and the silent ''vls'' cassettes are conserved while the vlsE sequence is recombined.  This suggests that the genetic variation mechanism occurs by copying segments of the 15 silent vls cassettes and completely replacing corresponding segments of ''vlsE'' sequences.  The resulting differences are centralized in the highly variable regions of the ''vls'' cassettes.  This allows for the constant evolution of the VR structures and evades the antibodies of the host immune system.
+Antigenic variation is the process by which an organism is able to evade its host’s immune system.  The antigenic variation that occurs in VlsE uses a complex genetic conversion mechanism that is seen to be concentrated in the VRs. The complex genetic system for VlsE is located near the right telomere on a 28-kb linear plasmid (lp28-1) in strains of ''B. burgdorferi''.  This [http://en.wikipedia.org/wiki/Locus_%28genetics%29 locus] has been shown to be a crucial element for the persistence and virulence of Lyme disease <ref name="Bankhead and Chaconas" />.  The ''vls'' antigenic variation locus consists of a ''vls'' expression site (''vlsE'') and 15 silent vls cassettes that reside just upstream of the site.  The ''vlsE'' cassette region, which is the variable domain and does not include the invariable amino or carboxyl termini, has approximately 92% DNA sequence identity with the silent vls cassettes.  However, the silent ''vls'' cassettes lack promoter sequences and are therefore not expressed.  Throughout the course of infection, the sequences for the flanking termini and the silent ''vls'' cassettes are conserved while the vlsE sequence is recombined.  This suggests that the genetic variation mechanism occurs by copying segments of the 15 silent vls cassettes and completely replacing corresponding segments of ''vlsE'' sequences.  The resulting differences are centralized in the highly variable regions of the ''vls'' cassettes.  This allows for the constant evolution of the VR structures and evades the antibodies of the host immune system.
 ==''Variable Regions''==