Identification of a family of mastermind-like transcriptional coactivators for mammalian notch receptors.
The molecular mechanisms by which Notch receptors induce diverse biological responses are not fully understood. We recently cloned a mammalian homologue of the Mastermind gene of Drosophila melanogaster, MAML1 (Mastermind-like-1 molecule) and determined that it functions as a transcriptional coactivator for Notch receptors. In this report, we characterize two additional genes in this Mastermind-like gene family: MAML2 and MAML3. The three MAML genes are widely expressed in adult tissues but exhibit distinct expression patterns in mouse early spinal cord development. All MAML proteins localize to nuclear bodies, share a conserved basic domain in their N termini that binds to the ankyrin repeat domain of Notch, and contain a transcriptional activation domain in their C termini. Moreover, as determined by using coimmunoprecipitation assays, each MAML protein was found to be capable of forming a multiprotein complex with the intracellular domain of each Notch receptor (ICN1 to -4) and CSL in vivo. However, MAML3 bound less efficiently to the ankyrin repeat domain of Notch1. Also, in U20S cells, whereas MAML1 and MAML2 functioned efficiently as coactivators with each of the Notch receptors to transactivate a Notch target HES1 promoter construct, MAML3 functioned more efficiently with ICN4 than with other forms of ICN. Similarly, MAML1 and MAML2 amplified Notch ligand (both Jagged2 and Delta1)-induced transcription of the HES-1 gene, whereas MAML3 displayed little effect. Thus, MAML proteins may modify Notch signaling in different cell types based on their own expression levels and differential activities and thereby contribute to the diversity of the biological effects resulting from Notch activation.
Wu
Lizi
L
Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
Sun
Tao
T
Kobayashi
Karla
K
Gao
Ping
P
Griffin
James D
JD
D000595:Amino Acid Sequence; D000818:Animals; D017487:Ankyrins / Q000737:chemistry; D015152:Blotting, Northern; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D029721:Drosophila Proteins; D006801:Humans; D017403:In Situ Hybridization; D019476:Insect Proteins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D005810:Multigene Family; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D051880:Receptors, Notch; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013116:Spinal Cord / Q000196:embryology; D013997:Time Factors; D015534:Trans-Activators / Q000737:chemistry* / Q000235:genetics; D014157:Transcription Factors; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D017487:Ankyrins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D019476:Insect Proteins; D008024:Ligands; C430872:MAML1 protein, human; C467909:MAML2 protein, mouse; C467910:MAML3 protein, mouse; D008565:Membrane Proteins; D009687:Nuclear Proteins; D051880:Receptors, Notch; D015534:Trans-Activators; D014157:Transcription Factors; C085316:mam protein, Drosophila; D008156:Luciferases