The basic domain of ATH5 mediates neuron-specific promoter activity during retina development.
In the developing retina, the gene encoding the beta3 subunit of the neuronal nicotinic receptor, a specific marker of retinal ganglion cells, is under the direct control of the atonal homolog 5 (ATH5) basic helix-loop-helix (bHLH) transcription factor. Although quite short (143 bp in length), the beta3 promoter has the remarkable capacity to discriminate between ATH5 and the other neuronal bHLH proteins expressed in the developing nervous system. We have identified three amino acids within the basic domain that confer specificity to the ATH5 protein. These residues do not mediate direct DNA binding but are required for interaction between ATH5 and chromatin-associated proteins during retina development. When misexpressed in neurons, the myogenic bHLH factor MyoD is also able to activate the beta3 gene. This, however, is achieved not by binding of the protein to the promoter but by dimerization of MyoD with a partner, a process that depends not on the basic domain but on the HLH domain. By sequestering an E-box-binding protein, MyoD relieves the active repression that blocks the beta3 promoter in most neurons. The mechanisms used by bHLH proteins to activate beta3 thus highlight how ATH5 is selected by the beta3 promoter and coordinates the derepression and transcriptional activation of the beta3 gene during the specification of retinal ganglion cells.
Skowronska-Krawczyk
Dorota
D
University of Lausanne, Eye Hospital Jules Gonin, Switzerland. Dorota.Skowronska@biochem.unige.ch
Matter-Sadzinski
Lidia
L
Ballivet
Marc
M
Matter
Jean-Marc
JM
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology*; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D002642:Chick Embryo; D002645:Chickens; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D004247:DNA / Q000737:chemistry; D017931:DNA Primers / Q000737:chemistry; D019281:Dimerization; D018274:Electroporation; D018507:Gene Expression Regulation, Developmental; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017570:MyoD Protein / Q000378:metabolism; D009420:Nervous System; D009474:Neurons / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D012160:Retina / Q000196:embryology*; D012165:Retinal Ganglion Cells / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D013997:Time Factors; D014162:Transfection
D051792:Basic Helix-Loop-Helix Proteins; D015500:Chloramphenicol O-Acetyltransferase; D002843:Chromatin; D004247:DNA; D017931:DNA Primers; D005982:Glutathione Transferase; D017570:MyoD Protein; D012333:RNA, Messenger