Sp1 deglycosylation after arsenic treatment. (A) Sp1 glycosylation was decreased after arsenic treatment, as detected by immunoblotting (IB) with O-linked GlcNAc-specific antibody (110.6 Ab) after immunoprecipitation (IP) with an anti-Sp1 antibody. The Sp1 antibody-detected signals serve as loading controls. (B) Sp1 deglycosylation was induced by glucose starvation (24 hours) or treatment with DON (40 μM for 24 hours). (C) Decrease in Sp1 glycosylation did not diminish in vivo Sp1 binding on the hTERT promoter, as determined by chromatin immunoprecipitation. (D) Deglycosylation of Sp1 did not result in decreased hTERT expression, as determined by quantitative RT-PCR. Error bars represent standard deviations from triplicate experiments.