Abstracts (poster) - Wissenschaft Online

Filip Senigl, Jiri Plachy, Jiri Hejnar
The CpG island core element protects retroviral vectors from
transcriptional silencing
Unmethylated CpG islands are known to maintain adjacent promoters transcriptionally
active. In the adenosine phosphoribosyltransferase gene-adjacent CpG island, the
protection from transcriptional silencing can be attributed to the short CpG-rich core
element containing Sp1 binding sites. We report here the insertion of this CpG island
core element, IE, into the long terminal repeat of a retroviral vector derived from Rous
sarcoma virus, which normally suffers from progressive transcriptional silencing in
mammalian cells. IE insertion into specific position between enhancer and promoter
sequences led to efficient protection of the integrated vector from silencing and gradual
CpG methylation in rodent and human cells. Individual cell clones with IE-modified
reporter vectors display high level of reporter expression for a sustained period and
without substantial variegation in the cell culture. The presence of Sp1 binding sites is
necessary for the protective effect of IE. Modified vectors with IE insertions are also
refractory to the transcriptional silencing during integration as evidenced by colonyforming
assay. We suggest that our strategy of anti-silencing protection by CpG island
core element may prove generally useful in retroviral vectors.
contact:
Jiri Hejnar
Institute of Molecular Genetics
hejnar@img.cas.cz
Videnska 1083
CZ-14220 Prague 6 (Czechia)