541C Poster - 07. Chromatin, epigenetics and genomics
Saturday April 09, 1:30 PM - 3:30 PM

Authors:
Safiyo Aden; Derrick carper; Heidi J.J Pipkin; Andrew M Arsham

Affiliation: Bemidji State University

Keywords:
e. heterochromatin; e. heterochromatin

Heterochromatin is a key genomic defense against invasive genetic elements, mitigating damage by inhibiting transposition, silencing gene expression, and reducing recombination at insertion sites. How genomes recognize and silence novel threats prior to establishing sequence-specific adaptive defenses like piRNAs is poorly understood. To investigate genome defense against novel repetitive DNA we carried out a transposition mutagenesis screen with a reporter construct expressing the white gene adjacent to a 256-copy tandem array of a 36 nt lac operator sequence from E. coli. Reporter gene expression was robust in the vast majority of transposition mutants recovered, while approximately 1% had variegated eye color suggesting epigenetic silencing by heterochromatin. Mapping of insertion sites by inverse PCR revealed that the lacO reporter construct can trigger silencing of actively transcribed euchromatin. Excision of the lacO array by FLP-FRT recombination suppressed variegation, restoring full reporter gene expression and demonstrating repeat-dependent silencing. Ectopic heterochromatinization a lacO tandem array may model disease processes like the silencing of triplet nucleotide expansions and evolutionary processes like centromere formation.