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FACT plays a major role in histone dynamics affecting VSG expression site control in T rypanosoma brucei
Author(s) -
Denninger Viola,
Rudenko Gloria
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12812
Subject(s) - biology , chromatin , microbiology and biotechnology , micrococcal nuclease , derepression , histone , gene knockdown , transcription (linguistics) , rna polymerase ii , promoter , genetics , gene expression , nucleosome , gene , psychological repression , linguistics , philosophy
Summary Chromatin remodelling is involved in the transcriptional regulation of the RNA polymerase I transcribed variant surface glycoprotein ( VSG ) expression sites ( ESs ) of T rypanosoma brucei . We show that the T . brucei FACT complex contains the P ob3 and S pt16 subunits, and plays a key role in ES silencing. We see an inverse correlation between transcription and condensed chromatin, whereby FACT knockdown results in ES derepression and more open chromatin around silent ES promoters. Derepressed ESs show increased sensitivity to micrococcal nuclease ( MNase ) digestion, and a decrease in histones at silent ES promoters but not telomeres. In contrast, FACT knockdown results in more histones at the active ES , correlated with transcription shut‐down. ES promoters are derepressed in cells stalled at the G 2/ M cell cycle stage after knockdown of FACT , but not in G 2/ M cells stalled after knockdown of cyclin 6. This argues that the observed ES derepression is a direct consequence of histone chaperone activity by FACT at the G 2/ M cell cycle stage which could affect transcription elongation, rather than an indirect consequence of a cell cycle checkpoint. These experiments highlight the role of the FACT complex in cell cycle‐specific chromatin remodelling within VSG ESs .