XrpFI, an amphibian transcription factor composed of multiple polypeptides immunologically related to the GA-binding protein alpha and beta subunits, is differentially expressed during Xenopus laevis development.
XrpFI, first identified in the extract of Xenopus laevis oocyte nuclei, binds to a proximal sequence of the L14 ribosomal protein gene promoter. Its target sequence, 5'-TAACCGGAAGTTTGT-3', is required to fully activate the promoter, and the two G's of the central motif are essential for factor binding and transcriptional activation; our data also suggest that XrpFI may play a role in cap site positioning. The binding site of XrpFI is homologous to the sequence recognized by the family of ets genes. Antibodies specific for Ets-1 and Ets-2 proteins did not react with XrpFI, but those raised against the rat alpha and beta GA-binding proteins both supershifted the retarded bands formed by XrpFI. The Xenopus polypeptides related to GA-binding protein alpha interact with DNA both as monomers and as heterodimers associated with beta-related proteins. Oocyte nuclei contain multiple forms of alpha- and beta-related proteins: the alpha-like proteins remain throughout development, while the pattern of the beta species changes in the embryonic stages examined. beta-like proteins are undetectable in the cleavage period up to the neurula stage, but at later stages, when ribosomal protein genes are actively transcribed, two beta-related polypeptides reappear.
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Dipartimento di Genetica e Biologia Molecolare, Università degli Studi di Roma La Sapienza, Rome, Italy.
Morabito
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Salvati
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Beccari
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Carnevali
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D000818:Animals; D001483:Base Sequence; D004247:DNA; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050783:Proto-Oncogene Proteins c-ets; D012269:Ribosomal Proteins / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D014158:Transcription, Genetic; D014982:Xenopus laevis
D004268:DNA-Binding Proteins; C494043:Ets1 protein, rat; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D012269:Ribosomal Proteins; D014157:Transcription Factors; C041174:ribosomal protein L14; D004247:DNA