M. Knossl et al., Expression of the human endogenous retrovirus HTDV/HERV-K is enhanced by cellular transcription factor YY1, J VIROLOGY, 73(2), 1999, pp. 1254-1261
The human endogenous retrovirus HTDV/HERV-K, which resides in moderate copy
numbers in the human genome, is expressed in a cell-type-specific manner,
predominantly in teratocarcinoma cells. We have analyzed the regulatory pot
ential of the 5' enhancer of the HERV-K long terminal repeat. Protein extra
cts of HERV-expressing teratocarcinoma cell lines (GH and Tera2) and nonexp
ressing HeLa and HepG2 cells form different protein complexes on the enhanc
er sequence as detected by electrophoretic mobility shift assays (EMSA). Us
ing competition EMSAs, DNase I footprinting, and supershift experiments, we
localized the binding site of these complexes to a 20-bp sequence within t
he enhancer and showed that the transcription factor YY1 is one component o
f the HERV-K enhancer complex. Replacement of the YY1 binding site with unr
elated sequences reduced expression of the luciferase gene as a reporter in
transient-transfection assays.