PMID- 15620659 OWN - NLM STAT- MEDLINE DCOM- 20050502 LR - 20191210 IS - 0960-9822 (Print) IS - 0960-9822 (Linking) VI - 14 IP - 24 DP - 2004 Dec 29 TI - The degradation of HFR1, a putative bHLH class transcription factor involved in light signaling, is regulated by phosphorylation and requires COP1. PG - 2296-301 AB - All developmental transitions throughout the life cycle of a plant are influenced by light. In Arabidopsis, multiple photoreceptors including the UV-A/blue-sensing cryptochromes (cry1-2) and the red/far-red responsive phytochromes (phyA-E) monitor the ambient light conditions. Light-regulated protein stability is a major control point of photomorphogenesis. The ubiquitin E3 ligase COP1 (constitutively photomorphogenic 1) regulates the stability of several light-signaling components. HFR1 (long hypocotyl in far-red light) is a putative transcription factor with a bHLH domain acting downstream of both phyA and the cryptochromes. HFR1 is closely related to PIF1, PIF3, and PIF4 (phytochrome interacting factor 1, 3 and 4), but in contrast to the latter three, there is no evidence for a direct interaction between HFR1 and the phytochromes. Here, we show that the protein abundance of HFR1 is tightly controlled by light. HFR1 is an unstable phosphoprotein, particularly in the dark. The proteasome and COP1 are required in vivo to degrade phosphorylated HFR1. In addition, HFR1 can interact with COP1, consistent with the idea of COP1 directly mediating HFR1 degradation. We identify a domain, conserved among several bHLH class proteins involved in light signaling , as a determinant of HFR1 stability. Our physiological experiments indicate that the control of HFR1 protein abundance is important for a normal de-etiolation response. FAU - Duek, Paula D AU - Duek PD AD - Department of Molecular Biology, University of Geneva, 30 quai Ernest Ansermet, 1211 Geneve 4, Switzerland. FAU - Elmer, Mireille V AU - Elmer MV FAU - van Oosten, Vivian R AU - van Oosten VR FAU - Fankhauser, Christian AU - Fankhauser C LA - eng PT - Comparative Study PT - Journal Article PT - Research Support, Non-U.S. Gov't PL - England TA - Curr Biol JT - Current biology : CB JID - 9107782 RN - 0 (Arabidopsis Proteins) RN - 0 (CRY1 protein, Arabidopsis) RN - 0 (Cryptochromes) RN - 0 (DNA Primers) RN - 0 (DNA, Complementary) RN - 0 (DNA-Binding Proteins) RN - 0 (Flavoproteins) RN - 0 (HFR1 protein, Arabidopsis) RN - 0 (Nuclear Proteins) RN - 0 (Transcription Factors) RN - 11121-56-5 (Phytochrome) RN - EC 2.3.2.27 (AT2G32950 protein, Arabidopsis) RN - EC 2.3.2.27 (Ubiquitin-Protein Ligases) SB - IM MH - Agrobacterium tumefaciens MH - Arabidopsis/*metabolism MH - Arabidopsis Proteins/genetics/*metabolism MH - Blotting, Western MH - Cryptochromes MH - DNA Primers MH - DNA, Complementary/genetics MH - DNA-Binding Proteins/genetics/*metabolism MH - Flavoproteins/physiology MH - Genetic Vectors MH - Immunoprecipitation MH - *Light MH - Nuclear Proteins/genetics/*metabolism MH - Phosphorylation MH - Phytochrome/physiology MH - Plants, Genetically Modified MH - *Signal Transduction MH - Transcription Factors/*metabolism MH - Two-Hybrid System Techniques MH - Ubiquitin-Protein Ligases EDAT- 2004/12/29 09:00 MHDA- 2005/05/03 09:00 CRDT- 2004/12/29 09:00 PHST- 2004/08/19 00:00 [received] PHST- 2004/10/06 00:00 [revised] PHST- 2004/10/19 00:00 [accepted] PHST- 2004/12/29 09:00 [pubmed] PHST- 2005/05/03 09:00 [medline] PHST- 2004/12/29 09:00 [entrez] AID - S0960-9822(04)00957-1 [pii] AID - 10.1016/j.cub.2004.12.026 [doi] PST - ppublish SO - Curr Biol. 2004 Dec 29;14(24):2296-301. doi: 10.1016/j.cub.2004.12.026.