The orphan receptor BmHNF-4 of the silkmoth Bombyx mori: ovarian and zygotic expression of two mRNA isoforms encoding polypeptides with different activating domains.
Two silkmoth nuclear receptor isoforms, BmHNF-4a and BmHNF-4b, that are related to the mammalian orphan receptor HNF-4, were characterized. Their characterization revealed that they differ from each other only in their 5' UTR and N-terminus of the predicted polypeptides. In ovarian tissue, the two receptors are expressed as a delayed response to 20-hydroxy-ecdysone and their expression increases during vitellogenesis. BmHNF-4 mRNA is localized in the cytoplasm of follicular cells and a binding activity that recognizes a mammalian HNF-4 response element is present in follicular cell nuclear extracts. BmHNF-4 mRNA is also present in the oocyte, the unfertilized egg and the early embryo, thus displaying a behavior reminiscent of maternal mRNA. Both mRNA isoforms are found in the embryo following fertilization and their abundance is modulated during ensuing embryogenesis. In contrast to the rather limited distribution of HNF-4 in mammalian tissues, BmHNF-4 is expressed in most larval and pharate adult tissues of the silkmoth.
Swevers
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Department of Medical Biochemistry, The University of Calgary, 3330 Hospital Dr. N.W., Calgary, Alberta T2N 4N1, Canada.
Iatrou
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005260:Female; D051557:Hepatocyte Nuclear Factor 4; D017403:In Situ Hybridization; D008675:Metamorphosis, Biological; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D009866:Oogenesis; D010053:Ovary / Q000254:growth & development / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015053:Zygote / Q000254:growth & development / Q000378:metabolism*
D004268:DNA-Binding Proteins; D051557:Hepatocyte Nuclear Factor 4; D016376:Oligonucleotides, Antisense; D010750:Phosphoproteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors