b HLH Basic Helix Loop Helix Family Protein

b. HLH - Basic Helix Loop Helix Family Protein Emily Eder HC 70 AL - 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 b. HLH proteins have on plants, namely Arabidopsis?

Characterization of b. HLH 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 b. HLH 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 b. HLH Family Proteins in Nonplant Eukaryotes • Myogenesis • Heart Development • Pancreatic Development • Neurogenesis

Affect of mutations in b. HLH family proteins in plant eukaryotes • Certain b. HLH 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

b. HLH 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