The architecture of variant surface glycoprotein gene expression sites in Trypanosoma brucei.
Trypanosoma brucei evades the immune system by switching between Variant Surface Glycoprotein (VSG) genes. The active VSG gene is transcribed in one of approximately 20 telomeric expression sites (ESs). It has been postulated that ES polymorphism plays a role in host adaptation. To gain more insight into ES architecture, we have determined the complete sequence of Bacterial Artificial Chromosomes (BACs) containing DNA from three ESs and their flanking regions. There was variation in the order and number of ES-associated genes (ESAGs). ESAGs 6 and 7, encoding transferrin receptor subunits, are the only ESAGs with functional copies in every ES that has been sequenced until now. A BAC clone containing the VO2 ES sequences comprised approximately half of a 330 kb 'intermediate' chromosome. The extensive similarity between this intermediate chromosome and the left telomere of T. brucei 927 chromosome I, suggests that this previously uncharacterised intermediate size class of chromosomes could have arisen from breakage of megabase chromosomes. Unexpected conservation of sequences, including pseudogenes, indicates that the multiple ESs could have arisen through a relatively recent amplification of a single ES.
Berriman
Matthew
M
The Wellcome Trust Sanger Institute, Hinxton CB10 1SA, UK.
Hall
Neil
N
Sheader
Karen
K
Bringaud
Frédéric
F
Tiwari
Bela
B
Isobe
Tomoko
T
Bowman
Sharen
S
Corton
Craig
C
Clark
Louise
L
Cross
George A M
GA
Hoek
Maarten
M
Zanders
Tyiesha
T
Berberof
Magali
M
Borst
Piet
P
Rudenko
Gloria
G
D000818:Animals; D000940:Antigenic Variation; D022202:Chromosomes, Artificial, Bacterial; D016054:DNA, Protozoan / Q000032:analysis; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D016615:Telomere / Q000235:genetics*; D014158:Transcription, Genetic; D014346:Trypanosoma brucei brucei / Q000235:genetics* / Q000378:metabolism*; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D016054:DNA, Protozoan; D014643:Variant Surface Glycoproteins, Trypanosoma