The role of LANP and ataxin 1 in E4F-mediated transcriptional repression

The leucine-rich acidic nuclear protein (LANP) belongs to the INHAT family of corepressors that inhibits histone acetyltrans-ferases. The mechanism by which LANP restricts its repression to specific genes is unknown. Here, we report that LANP forms a complex with transcriptional repressor E4F and modulates its activity. As LANP interacts with ataxin 1-a protein mutated in the neurodegenerative disease spinocerebellar ataxia type 1 (SCA1)-we tested whether ataxin 1 can alter the E4F-LANP interaction. We show that ataxin 1 relieves the transcriptional repression induced by the LANP-E4F complex by competing with E4F for LANP. These results provide the first functional link, to our knowledge, between LANP and ataxin 1, and indicate a potential mechanism for the transcriptional aberrations observed in SCA1.