Xenopus laevis c-myc I and II genes: molecular structure and developmental expression.
The structure of the two Xenopus laevis c-myc I and c-myc II genes has been investigated by isolating and sequencing genomic and cDNAs clones. In oocytes, c-myc I mRNAs represent 80-90% of the overall amount of c-myc transcripts. The c-myc I expression is controlled primarily by two differentially regulated tandem promoters P1 and P2 which are separated by 50 bases. During oogenesis, maternal c-myc I mRNAs, are transcribed from both promoters whereas zygotic transcripts seem to initiate only from the P2 promoter. Sequence comparison between the promoter regions of c-myc I and II genes reveals the insertion in the c-myc I promoter region, between positions -831 and -389 relative to the P1 start site of a repetitive element. Comparison of X.laevis and mammalian c-myc promoter sequences reveals furthermore the conservation of cis-regulatory elements, including a motif known to be a negative regulator of the human c-myc transcription, a purine rich region, a binding site for the E2-F transcription factor and three SP1 binding sites. Finally, we report characterization of a new c-myc I mRNA which differ at the 5' end. Transcripts are possibly initiated at a putative alternative promoter located further upstream in the genome, and undergoes alternative splicing.
Principaud
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E
Université de Genève, Département de Biologie Cellulaire, Switzerland.
Spohr
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G
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000235:genetics*
C489427:MYC protein, human; C489428:Myc protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D029867:Xenopus Proteins; C069483:c-Myc1 protein, Xenopus; C069482:c-myc II protein, Xenopus; D004247:DNA