Mutant huntingtin represses CBP, but not p300, by binding and protein degradation.
Huntington's disease can be used as a model to study neurodegenerative disorders caused by aggregation-prone proteins. It has been proposed that the entrapment of transcription factors in aggregates plays an important role in pathogenesis. We now report that the transcriptional activity of CBP is already repressed in the early time points by soluble mutant huntingtin, whereas the histone acetylase activity of CBP/p300 is gradually diminished over time. Mutant huntingtin bound much stronger to CBP than normal huntingtin, possibly contributing to repression. Especially at the later time points, CBP protein level was gradually reduced via the proteasome pathway. In sharp contrast, p300 was unaffected by mutant huntingtin. This selective degradation of CBP was absent in spinocerebellar ataxia 3. Thus, mutant huntingtin specifically affects CBP and not p300 both at the early and later time points, via multiple mechanisms. In addition to the reduction of CBP, also the altered ratio of these closely related histone acetyltransferases may affect chromatin structure and transcription and thus contribute to neurodegeneration.
Cong
Shu-Yan
SY
CBG-Center of Human and Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands.
Pepers
Barry A
BA
Evert
Bernd O
BO
Rubinsztein
David C
DC
Roos
Raymund A C
RA
van Ommen
Gert-Jan B
GJ
Dorsman
Josephine C
JC
D000818:Animals; D050882:CREB-Binding Protein; D050881:E1A-Associated p300 Protein; D005786:Gene Expression Regulation; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000378:metabolism* / Q000503:physiopathology; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D016716:PC12 Cells; D011485:Protein Binding; D051381:Rats; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection
C499524:Htt protein, rat; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D015534:Trans-Activators; D050882:CREB-Binding Protein; C494365:Crebbp protein, rat; D050881:E1A-Associated p300 Protein; C494362:Ep300 protein, rat