Molecular cloning of polybromo, a nuclear protein containing multiple domains including five bromodomains, a truncated HMG-box, and two repeats of a novel domain.
A number of transcription factors that act as adaptor proteins have been found to contain an 87 amino acid domain called the bromodomain. In a study to identify and characterise bromodomain proteins expressed in chicken cells, a novel gene has been isolated which encodes five repeats of the bromodomain. In addition, the encoded protein, termed polybromo, contains four other domains: an unusual truncated HMG box, two repeats of a novel domain which we term the BAH domain and a sequence related to a region within the regulatory domain of the DNA cytosine-5 methyltransferase enzyme. Polybromo was found to be related to a yeast protein U19102 which has two bromo domains, a BAH domain and the DNA methyltransferase-related sequence. Antibodies that were raised against polybromo were used in confocal microscopy analysis to show that the 180-kDa polybromo protein is located within the nucleus but excluded from the nucleolus. Gel filtration analysis of nuclear extracts demonstrate that polybromo is part of a large complex with a mass of approximately 2 million dalton.
Chester Beatty Laboratories, Institute of Cancer Research, London, UK.
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Nicolas
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Goodwin
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics*; D004268:DNA-Binding Proteins; D008780:Methyltransferases / Q000235:genetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics*
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C102195:PBRM1 protein, human; D014157:Transcription Factors; D008780:Methyltransferases