Poster Sessions

V -32

Atreyi Chatterjee

A. Chatterjee, Y. E. Leem, F. Kelly, H. Levin

The chromodomain of Tf1 integrase mediates both binding of cDNA and target site selection.

The LTR retrotransposon Tf1 of Schizosaccharomyces pombe integrates specifically into the promoters of pol II transcribed genes. Its integrase contains a C-terminal chromodomain. The ability of many chromodomains to bind to the N-terminal tails of histone H3 suggested that the chromodomain in Tf1 might play a critical role in directing integration to its target sites. To test this we generated transposons with single amino acids substitutions in highly conserved residues of the chromodomain and we created a chromodomain deleted (CHD ∆) mutant. All of these mutations significantly reduced transposition activity. Most mutants showed no reduction in the production of integrase or cDNA. By measuring the homologous recombination between cDNA and the plasmid copy of Tf1, we found the mutations did not reduce the import of cDNA into the nucleus. Chromatin immunoprecipitation assays revealed that the mutations caused a 3-fold reduction in the binding of integrase to the cDNA. These data indicate that the chromodomain contributed directly to integration. Results of a target plasmid assay showed the deletion of the chromodomain resulted in a drastic reduction in the preference for pol II promoters. Collectively, these data indicate that the chromodomain mediates binding of cDNA and plays a role in efficient targeting.