Ecdysone induces transcription and amplification in Sciara coprophila DNA puff II/9A

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.07.018 Byline: Michael S. Foulk, Chun Liang, Nan Wu, Hannah G. Blitzblau, Heidi Smith, Daniel Alam, Maneesh Batra, Susan A. Gerbi Keywords: DNA amplification; Ecdysone; Sciara coprophila; DNA puff; EcRE; Amplification factor Abstract: DNA replication is normally tightly regulated to ensure the production of only one copy of the genome per cell cycle. However, DNA puffs of the salivary gland giant polytene chromosomes of Sciara coprophila undergo DNA amplification during the normal course of development, overriding this control. This developmental strategy provides more template for the production of large amounts of protein needed for pupation. We have focused on DNA puff II/9A, which amplifies [approximately equal to]17-fold over the rest of the genome. Evidence presented here suggests that DNA amplification at this locus is controlled by the steroid hormone ecdysone, the master regulator of insect development. Explanted, pre-amplification stage salivary glands undergo premature amplification when incubated with ecdysone. Injection of ecdysone into pre-amplification stage larvae induces amplification. Ecdysone also induces transcription of the II/9A genes. We report the presence of a putative ecdysone response element directly adjacent to the origin recognition complex (ORC)-binding site in the II/9A origin and demonstrate that it is efficiently bound by the Sciara ecdysone receptor. These results implicate ecdysone in the regulation of DNA amplification in Sciara and suggest the ecdysone receptor may be the elusive amplification factor. This would be a new role for this transcription factor. Author Affiliation: Brown University, 69 Brown St.-J.W. Wilson Laboratory, Providence, RI 02912, USA Article History: Received 17 May 2006; Revised 13 July 2006; Accepted 14 July 2006