The ∆3–4, ∆2–6, and ∆5–10 HIF1α variants, as well as
wild-type HIF1α, were introduced into 769-P VHL–/– renal
carcinoma cells, using the doxycycline-inducible retroviral
expression vector described above. Notably, each variant,
except for the ∆5–10 one, preserves the proper reading
frame. An N-terminal hemagglutinin (HA) epitope tag was
introduced to facilitate the detection of wild-type and mutant
HIF1α proteins after induction with doxycycline. Eachvariant migrated in accordance with its predicted molecular
weight and, with the exception of the ∆2–6 variant, was produced
at levels that were similar to those of wild-type HIF1α
(Fig. 6B).