Ectopic heterochromatin triggered by insertion of repetitive DNA is temperature-sensitive
Authors: Melissa Sawyer 1,2; Safiyo Aden 1,2; Zayid Dakane 1,2; Nathan Dupre 1,2; Jack Jurmu 1,2; Hunter Lindsay 1,2; Heidi J.J. Pipkin 1,2; Anthony Ruiz 1,2; Jessica Xiong 1,2; Luke Ziegler 1,2; Andrew M. Arsham 1
Affiliations: 1) Bemidji State University, Bemidji, MN; 2) North Hennepin Community College, Brooklyn Park, MN
Keywords: e. heterochromatin; r. piRNA
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, mobilizing a reporter construct expressing the white gene adjacent to a 256-copy tandem array of the lac operator sequence from E. coli. We isolated insertional mutants with variegated eye color suggesting silencing by heterochromatin. Surprisingly, the observed variegation is exceptionally sensitive to rearing temperature despite different genomic locations and chromatin contexts. Contrary to classical studies of position effect variegation at constitutive heterochromatin, ectopic heterochromatin variegation was suppressed when flies were reared at 18°C and enhanced at 25°C. Suppression of variegation at lower growth temperatures may provide clues to the genetic and biochemical mechanisms of genome defenses against novel invasive DNA.