Fig 6. Ube3a unsilencing is TOP1cc-dependent.
(A) Ube3am-/p+::Top1fl/fl (AS) cortical neuron cultures were transfected with tdTomato-P2A-CRE and GFP, GFP-TOP1, or the TOP1 cleavage complex mimetic GFP-TOP1 T718A at DIV 6. Cells were then fixed at DIV 13. (B) Quantification of UBE3A immunostaining. Values are normalized to UBE3A intensity in the GFP control. Mean ± s.e.m., unpaired student’s t-test; * p < 0.05, n = 5 culture sets. (C) Model depicting TOP1 regulation of gene transcription in neurons. Most genes (n = 500) that are downregulated following TOP1 disruption are TOP1cc-dependent and long (on average ~318 kb), while a minority of genes (n = 33) are TOP1cc-independent and short (on average ~43 kb). Expression of some genes (n = 80), are sensitive to TOP1cc-dependent or -independent mechanisms and are exceptionally long (on average ~444 kb). Listed are potential factors that may coordinate with TOP1 to allow for these distinct mechanisms of TOP1-dependent gene regulation.