Polyglutamine represses cAMP-responsive-element-mediated transcription without aggregate formation.
Transcriptional dysregulation, particularly cAMP-responsive-element-mediated transcriptional repression, has been implicated in expanded polyglutamine diseases. However, it has not been clarified whether this transcriptional repression is a cause or result of neurodegeneration. Furthermore, the association between aggregates of expanded polyglutamine stretches and transcriptional repression is not clear. We established isogenic cell lines with polyglutamine stretches, which also expressed d2EGFP under the control of cAMP-responsive elements. In this system, the polyglutamine stretch repressed cAMP-responsive-element-mediated transcription without the formation of macroscopic expanded polyglutamine aggregates. Furthermore, aggregate formation did not have an adverse effect on the repression of transcriptional activity. The results demonstrated that the repression of cAMP-responsive-element-mediated transcription is an early event caused by a soluble form of polyglutamine stretch.