bHLH - Basic Helix Loop Helix Family Protein Emily Eder HC 70AL - Spring 2005

The Basic Helix Loop Helix What characterizes the proteins in this family? Are there any known functions? –In nonplant eukaryotes? –In plant eukaryotes, namely Arabidopsis? What affect do mutant bHLH proteins have on plants, namely Arabidopsis?

Characterization of bHLH Family Proteins Two distinct regions: –Basic Region –HLH Region Basic Region –involved in DNA binding HLH Region –functions as a dimerization domain

Known functions? Plants? Mammals?

Function of bHLH Family Proteins Important regulatory components of transcription factors Control a diversity of processes: –Cell proliferation –Cell lineage Formation of homodimers and heterodimers

Effect of mutant bHLH Family Proteins in Nonplant Eukaryotes Myogenesis Heart Development Pancreatic Development Neurogenesis

Affect of mutations in bHLH family proteins in plant eukaryotes Certain bHLH proteins affect photomorphogenic responses, including germination, blocking of greening, and expression of some light-regulated genes Phytochromes (primary photoreceptors) affecting induction of germination to floral growth in higher plants

bHLH Family Proteins Two regions - basic and HLH Control a multitude of processes Formation of homodimers and heterodimers Mutants in non-plant eukaryotes have extensive affects Mutant phenotypes in plant eukaryotes, namely Arabidopsis, are constantly being discovered