Oligomerisation of the developmental regulator proline rich homeodomain (PRH/Hex) is mediated by a novel proline-rich dimerisation domain.
Homeodomain proteins regulate multiple developmental pathways by altering gene expression temporally and in a tissue-specific fashion. The Proline Rich Homeodomain protein (PRH/Hex) is a transcription factor and an essential regulator of embryonic development and haematopoiesis. Recent discoveries have implicated self-association as an important feature of transcription factor function. Here, we show using a variety of techniques including gel-filtration, analytical ultracentrifugation, electron microscopy and in vitro cross-linking, that purified recombinant PRH is oligomeric and we use in vivo cross-linking to confirm that this protein exists as oligomers in cells. This is the first demonstration that a homeodomain protein can oligomerise in vivo. Consistent with these findings we show that a fraction of endogenous and exogenous PRH appears as discrete foci within the nucleus and at the nuclear periphery. The N-terminal domain of PRH is involved in the regulation of cell proliferation and transcriptional repression and can make multiple protein-protein interactions. We show that this region of PRH contains a novel proline-rich dimerisation domain that mediates oligomerisation. We propose a model that explains how PRH forms oligomers and we discuss how these oligomers might control transcription.
Soufi
Abdenour
A
Department of Biochemistry, University of Bristol, University Walk, Bristol BS81TD, UK.
Smith
Corinne
C
Clarke
Anthony R
AR
Gaston
Kevin
K
Jayaraman
Padma-Sheela
PS
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002522:Chlorocebus aethiops; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D020014:K562 Cells; D008854:Microscopy, Electron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011392:Proline / Q000737:chemistry; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012996:Solutions; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
C078492:HHEX protein, human; D018398:Homeodomain Proteins; D011994:Recombinant Proteins; D012996:Solutions; D014157:Transcription Factors; D004247:DNA; D011392:Proline