The brain-specific actin-related protein ArpN alpha interacts with the transcriptional co-repressor CtBP

Actin-related protein (Arp) is found in many chromatin remodeling and histone acetyltransferase complexes. We previously identified ArpN alpha as an isoform of ArpN beta/BAF53, which is included in mammalian SWI/SNF chromatin remodeling complex, and showed that ArpN alpha is a potential component of the complex. Although it has a structure highly similar to ArpN beta/BAF53, ArpN alpha is expressed exclusively in brain and in neural differentiated embryonal carcinoma cells. Since ArpN alpha possesses a region that shows low similarity to ArpN beta/BAF53, we hypothesized that proteins interacting with this region contribute to the ArpN alpha-specific function in brain. Here we showed that ArpN alpha, but not ArpN beta/BAF53, interacts with the transcriptional co-repressor CtBP (C-terminal binding protein). Transactivation by the SWI/SNF complex and glucocorticoid receptor was repressed by the CtBP in the presence of ArpN alpha. These findings suggest that SWI/SNF complex containing ArpN alpha might regulate certain genes involved in brain development and/or its function differently from SWI/SNF complex containing ArpN beta/BAF53.