The positioning of vsg genes in the genome is tightly linked to regulation of expression; the actively expressed vsg is duplicated into one of the bloodstream expression sites located in the sub-telomeric regions (reviewed in [ 56, 57]).
Taken together, these experiments suggest that regulatory regions that are normally resident on the autosomes and actively drive expression in the testes, have greatly reduced activity in this tissue when they are relocated to the X chromosome.
This analysis suggests that Pax6 actively promotes expression of specific genes in one tissue, i.e. embryonic cortex, while simultaneously repressing their expression in a different cell type, i.e. lens.
In proliferating myoblasts, MyoD is associated with histone deacetylases (HDACs), the histone methyltransferase Suv39h1 and heterochromatin protein HP1, and might actively inhibit expression of its target genes by inducing a local repressive chromatin structure [24], [28], [29].
Increased cytoplasmic HuR levels have previously been described in situations where HuR actively influences expression of cytoplasmic targets [ 18, 47, 48].
To further explore transcriptional regulatory circuits among Tbx3, Nkx2.5, Gata4, and Tbx5, we examined how overexpression of these transcription factors actively regulated expression of other transcription factors.
In basal breast cancers and head and neck squamous cell carcinomas, ΔNp63 α acts as a pro-survival factor and a mediator of chemo-resistance that actively represses expression of pro-apoptotic effectors.
DNA methylation may actively alter gene expression, itself be altered by gene expression, or both methylation and expression may be jointly determined by a distinct genetic feature.
Leu3p binding to UASLEU should actively repress the expression of GFP in the absence of α-IPM and activate transcription in the presence of α-IPM [15].
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