Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 102, Issue 51, Pages 18730-18735Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0507693102
Keywords
acclimation; copper homeostasis; hypoxia; metal; transcription factor
Categories
Funding
- NIGMS NIH HHS [GM42143, R01 GM042143, R37 GM042143] Funding Source: Medline
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The CRR1 (Copper Response Regulator) locus, required for both activating and repressing target genes of a copper- and hypoxiasensing pathway in Chlamydomonas, encodes a 1,232-residue candidate transcription factor with a plant-specific DNA-binding domain named SBP, ankyrin repeats, and a C-terminal Cys-rich region, with similarity to a Drosophila metallothionein. The recombinant SBP domain of Crr1 shows zinc-dependent binding to functionally defined copper-response elements associated with the CYC6 and CPX1 promoters that contain a critical GTAC core sequence. Competition experiments indicate equivalent selectivity for copper-response elements from either promoter and 10-fold greater selectivity for the wild-type sequence vs. a sequence carrying a single mutation in the GTAC core. The SBP domain of Chlamydomonals Crr1 binds also to a related GTAC-containing sequence in the Arabidopsis AP1 promoter that is the binding site of a defining member of the SBP family of DNA-binding proteins. Chlamydomonas Crr1 is most similar to a subset of the Arabidopsis SBP domain proteins, which include SPL1, SPL7, and SPL12. The abundance of the CRR1 mRNA is only marginally copper-responsive, and although two mRNAs that differ with respect to splicing of the first intron are detected, there is no indication that the splicing event is regulated by metal nutrition or hypoxia. It is likely that the dramatic copper-responsive action of Crr1 occurs at the level of the polypeptide.
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