The interaction with HMG20a/b proteins suggests a potential role for beta-dystrobrevin in neuronal differentiation.
alpha and beta dystrobrevins are cytoplasmic components of the dystrophin-associated protein complex that are thought to play a role as scaffold proteins in signal transduction and intracellular transport. In the search of new insights into the functions of beta-dystrobrevin, the isoform restricted to non-muscle tissues, we performed a two-hybrid screen of a mouse cDNA library to look for interacting proteins. Among the positive clones, one encodes iBRAF/HMG20a, a high mobility group (HMG)-domain protein that activates REST (RE-1 silencing transcription factor)-responsive genes, playing a key role in the initiation of neuronal differentiation. We characterized the beta-dystrobrevin-iBRAF interaction by in vitro and in vivo association assays, localized the binding region of one protein to the other, and assessed the kinetics of the interaction as one of high affinity. We also found that beta-dystrobrevin directly binds to BRAF35/HMG20b, a close homologue of iBRAF and a member of a co-repressor complex required for the repression of neural specific genes in neuronal progenitors. In vitro assays indicated that beta-dystrobrevin binds to RE-1 and represses the promoter activity of synapsin I, a REST-responsive gene that is a marker for neuronal differentiation. Altogether, our data demonstrate a direct interaction of beta-dystrobrevin with the HMG20 proteins iBRAF and BRAF35 and suggest that beta-dystrobrevin may be involved in regulating chromatin dynamics, possibly playing a role in neuronal differentiation.
Artegiani
Benedetta
B
Department of Cell Biology and Neuroscience, National Center for Rare Diseases, Istituto Superiore di Sanità, Rome 00161, Italy.
Labbaye
Catherine
C
Sferra
Antonella
A
Quaranta
Maria Teresa
MT
Torreri
Paola
P
Macchia
Gianfranco
G
Ceccarini
Marina
M
Petrucci
Tamara C
TC
Macioce
Pompeo
P
D000818:Animals; D019556:COS Cells; D018797:Cell Cycle Proteins; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D002843:Chromatin / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000378:metabolism*; D049029:Dystrophin-Associated Proteins / Q000502:physiology*; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D051379:Mice; D009136:Muscular Dystrophies / Q000378:metabolism; D009474:Neurons / Q000166:cytology*; D051381:Rats; D020349:Surface Plasmon Resonance
D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D049029:Dystrophin-Associated Proteins; C408987:HMG20A protein, human; C000625244:HMG20B protein, human; D006609:High Mobility Group Proteins; C507322:Hmg20a protein, mouse; C400291:Hmg20b protein, mouse; C098885:dystrobrevin