The POU factor Oct-25 regulates the Xvent-2B gene and counteracts terminal differentiation in Xenopus embryos.
The Xvent-2B promoter is regulated by a BMP-2/4-induced transcription complex comprising Smad signal transducers and specific transcription factors. Using a yeast one-hybrid screen we have found that Oct-25, a Xenopus POU domain protein related to mammalian Oct-3/4, binds as an additional factor to the Xvent-2B promoter. This interaction was further confirmed by both in vitro and in vivo analyses. The Oct-25 gene is mainly transcribed during blastula and gastrula stages in the newly forming ectodermal and mesodermal germ layers. Luciferase reporter gene assay demonstrated that Oct-25 stimulates transcription of the Xvent-2B gene. This stimulation depends on the Oct-25 binding site and the bone morphogenetic protein-responsive element. Furthermore, Oct-25 interacts in vitro with components of the Xvent-2B transcription complex, like Smad1/4 and Xvent-2. Overexpression of Oct-25 results in anterior/posterior truncations and lack of differentiation for neuroectoderm- and mesoderm-derived tissues including blood cells. This effect is consistent with an evolutionarily conserved role of class V POU factors in the maintenance of an undifferentiated cell state. In Xenopus, the molecular mechanism underlying this process might be coupled to the expression of Xvent proteins.
Abteilung Biochemie, Universität Ulm, Albert-Einstein-Allee 11, D-89081, Germany.
Ying
Y
Cao
Sigrun
S
Knöchel
Cornelia
C
Donow
Josef
J
Miethe
Eckhard
E
Kaufmann
Walter
W
Knöchel
D000818:Animals; D001483:Base Sequence; D001757:Blastomeres / Q000166:cytology / Q000502:physiology; D002454:Cell Differentiation; D003001:Cloning, Molecular; D018983:DNA Footprinting; D017931:DNA Primers; D003850:Deoxyribonuclease I; D004625:Embryo, Nonmammalian / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics*; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics*
D017931:DNA Primers; D018398:Homeodomain Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; C099992:ventx2.1 protein, Xenopus; D003850:Deoxyribonuclease I