title: Human cryptochrome-1 confers light independent biological activity in transgenic Drosophila correlated with flavin radical stability.
abstract: Cryptochromes are conserved flavoprotein receptors found throughout the biological kingdom with diversified roles in plant development and entrainment of the circadian clock in animals. Light perception is proposed to occur through flavin radical formation that correlates with biological activity in vivo in both plants and Drosophila. By contrast, mammalian (Type II) cryptochromes regulate the circadian clock independently of light, raising the fundamental question of whether mammalian cryptochromes have evolved entirely distinct signaling mechanisms. Here we show by developmental and transcriptome analysis that Homo sapiens cryptochrome--1 (HsCRY1) confers biological activity in transgenic expressing Drosophila in darkness, that can in some cases be further stimulated by light. In contrast to all other cryptochromes, purified recombinant HsCRY1 protein was stably isolated in the anionic radical flavin state, containing only a small proportion of oxidized flavin which could be reduced by illumination. We conclude that animal Type I and Type II cryptochromes may both have signaling mechanisms involving formation of a flavin radical signaling state, and that light independent activity of Type II cryptochromes is a consequence of dark accumulation of this redox form in vivo rather than of a fundamental difference in signaling mechanism.
authors.affiliation: Université Paris VI, Paris, France.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Vieira
authors.forename: Alex R
authors.initials: AR
authors.lastname: Jones
authors.forename: Antoine
authors.initials: A
authors.lastname: Danon
authors.forename: Michiyo
authors.initials: M
authors.lastname: Sakuma
authors.forename: Nathalie
authors.initials: N
authors.lastname: Hoang
authors.forename: David
authors.initials: D
authors.lastname: Robles
authors.forename: Shirley
authors.initials: S
authors.lastname: Tait
authors.forename: Derren J
authors.initials: DJ
authors.lastname: Heyes
authors.forename: Marie
authors.initials: M
authors.lastname: Picot
authors.forename: Taishi
authors.initials: T
authors.lastname: Yoshii
authors.forename: Charlotte
authors.initials: C
authors.lastname: Helfrich-Förster
authors.forename: Guillaume
authors.initials: G
authors.lastname: Soubigou
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Coppee
authors.forename: André
authors.initials: A
authors.lastname: Klarsfeld
authors.forename: Francois
authors.initials: F
authors.lastname: Rouyer
authors.forename: Nigel S
authors.initials: NS
authors.lastname: Scrutton
authors.forename: Margaret
authors.initials: M
authors.lastname: Ahmad
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002940:Circadian Rhythm / Q000502:physiology*; D056931:Cryptochromes / Q000302:isolation & purification / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D003624:Darkness; D004330:Drosophila; D005415:Flavins / Q000378:metabolism*; D020869:Gene Expression Profiling; D006801:Humans; D008675:Metamorphosis, Biological / Q000502:physiology*; D046228:Microarray Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*
chemical_list: C538963:CRY1 protein, human; D056931:Cryptochromes; D017931:DNA Primers; D005415:Flavins