Nucleosomes are depleted at the VSG expression site transcribed by RNA polymerase I in African trypanosomes.
Eukaryot Cell
; 9(1): 148-54, 2010 Jan.
Article
en En
| MEDLINE
| ID: mdl-19915072
ABSTRACT
In most eukaryotes, RNA polymerase I (Pol I) exclusively transcribes long arrays of identical rRNA genes (ribosomal DNA [rDNA]). African trypanosomes have the unique property of using Pol I to also transcribe the variant surface glycoprotein VSG genes. VSGs are important virulence factors because their switching allows trypanosomes to escape the host immune system, a mechanism known as antigenic variation. Only one VSG is transcribed at a time from one of 15 bloodstream-form expression sites (BESs). Although it is clear that switching among BESs does not involve DNA rearrangements and that regulation is probably epigenetic, it remains unknown why BESs are transcribed by Pol I and what roles are played by chromatin structure and histone modifications. Using chromatin immunoprecipitation, micrococcal nuclease digestion, and chromatin fractionation, we observed that there are fewer nucleosomes at the active BES and that these are irregularly spaced compared to silent BESs. rDNA coding regions are also depleted of nucleosomes, relative to the rDNA spacer. In contrast, genes transcribed by Pol II are organized in a more compact, regularly spaced, nucleosomal structure. These observations provide new insight on antigenic variation by showing that chromatin remodeling is an intrinsic feature of BES regulation.
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Trypanosoma brucei brucei
/
ARN Polimerasa I
/
Nucleosomas
/
Glicoproteínas Variantes de Superficie de Trypanosoma
Idioma:
En
Revista:
Eukaryot Cell
Asunto de la revista:
BIOLOGIA MOLECULAR
Año:
2010
Tipo del documento:
Article
País de afiliación:
Estados Unidos