Involvement of Rel/NF-kappaB in regulation of ascidian notochord formation.
The Rel/NF-kappaB family is known to be involved in a wide variety of biological processes, including morphogenesis. In the present study, two protochordate cDNA clones encoding Rel/NF-kappaB proteins, named As-rel1 and As-rel2, were isolated from a fertilized egg cDNA library of the ascidian Halocynthia roretzi. The As-rel1 protein is a typical Rel/NF-kappaB family member, containing a Rel homology domain, a nuclear localization sequence and a C-terminal putative transcription activation domain, while the As-rel2 protein is a novel Rel/NF-kappaB family member that lacks a nuclear localization sequence and the C-terminal domain. Northern blot analyses showed that both transcripts were maternally expressed and that their expression changed during development of H. roretzi embryos. Although injection of the As-rel2 mRNA into H. roretzi fertilized eggs had little effect on embryonic development, injection of the As-rel1 mRNA interfered greatly with notochord formation, resulting in a shortened tail with a reduced number of notochord cells. In contrast, embryos co-injected with As-rel1 and As-rel2 mRNA developed normally, indicating that the As-rel2 protein rescued the defect in notochord formation induced by the injection of As-rel1 mRNA alone. These results strongly suggest that the As-rel1 protein functions as a suppressor in ascidian notochord formation, while the As-rel2 protein has an antagonistic effect on the action of the As-rel1 protein.
Shimada
M
M
Department of Biochemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
Satoh
N
N
Yokosawa
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000235:genetics / Q000502:physiology*; D009672:Notochord / Q000254:growth & development*; D010802:Phylogeny; D051996:Transcription Factor RelA; D014561:Urochordata / Q000196:embryology*
D017931:DNA Primers; D016328:NF-kappa B; D051996:Transcription Factor RelA