Loss of CBP acetyltransferase activity by PHD finger mutations in Rubinstein-Taybi syndrome.
Disruption of one copy of the human CREB binding protein (CBP or CREBBP) gene leads to the Rubinstein-Taybi syndrome (RTS), a developmental disorder characterized by retarded growth and mental functions, broad thumbs, broad big toes and typical facial abnormalities. The CREB binding protein (CBP) is an essential transcriptional coactivator for many different transcription factors. CBP has the intrinsic ability to acetylate histones and other proteins, which is regarded as an important step in transcription activation. In vitro studies have shown that this enzymatic activity critically depends on the integrity of a plant homeodomain (PHD)-type zinc finger in the HAT domain of CBP. We therefore investigated whether PHD finger mutations are present in RTS patients. Mutational analysis of 39 patients revealed eight novel heterozygous mutations in the HAT domain of CBP, one of which alters a conserved PHD finger amino acid (E1278K), while a second mutation deletes exon 22, which encodes the central region of the PHD finger. Functional analysis of these RTS-associated PHD finger mutants showed that they lacked in vitro acetyltransferase activity towards histones and CBP itself and displayed reduced coactivator function for the transcription factor CREB. Importantly, in EBV-transformed lymphoblastoid cells from the exon 22 deletion patient we found approximately 50% less endogenous CBP HAT activity. These findings therefore underscore the functional importance of the PHD finger in vivo and imply that reduction of CBP HAT activity, as exemplified here by disruption of the PHD finger, is sufficient to cause RTS.
Kalkhoven
Eric
E
Department of Molecular Cell Biology, MGC Centre for Biomedical Genetics, Leiden University Medical Centre, Wassenaarseweg 72, 2333 AL Leiden, The Netherlands.
Roelfsema
Jeroen H
JH
Teunissen
Hans
H
den Boer
Annemieke
A
Ariyurek
Yavuz
Y
Zantema
Alt
A
Breuning
Martijn H
MH
Hennekam
Raoul C M
RC
Peters
Dorien J M
DJ
D000123:Acetyltransferases / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D015153:Blotting, Western; D002869:Chromosome Aberrations; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics* / Q000378:metabolism*; D005091:Exons; D006579:Heterozygote; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012415:Rubinstein-Taybi Syndrome / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D014407:Tumor Cells, Cultured
D017362:Cyclic AMP Response Element-Binding Protein; D000123:Acetyltransferases