New AUG initiation codons in a long 5' UTR create four dominant negative alleles of the Drosophila C2H2 zinc-finger gene ovo.
Promoters active in the germline produce OVO-A and OVO-B mRNAs encoding isoforms of a putative transcription factor. The isoforms have a common C2H2 zinc-finger domain but different N-termini that include potential effector domains. Single point mutations in three dominant-negative ovoD mutations result in new in-frame initiation codons in OVO-B mRNAs and amino acid substitutions within charged regions of OVO-A proteins. Three lines of evidence suggest that the dominant activity is due to the new initiation codons in OVO-B mRNAs and not the amino acid substitutions in OVO-A. First, we made a fourth ovoD allele by inserting a new in-frame AUG. This ovoD4 allele encodes a nearly full-length OVO-A isoform from OVO-B mRNAs. Second, engineered stop codons in ovoD1 downstream of the new AUG abolished dominant negative activity. Third, a substantial deletion of an OVO-A region encoding a highly charged amino acid domain fully rescued loss-of-function ovo alleles. These data suggest that ovoD mutations result in inappropriate expression of OVO-A in the female germline.
Andrews
J
J
Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA.
Levenson
I
I
Oliver
B
B
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D018387:Codon, Initiator / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics*; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins; D005260:Female; D005298:Fertility / Q000235:genetics; D005799:Genes, Dominant / Q000235:genetics*; D017344:Genes, Insect / Q000235:genetics; D008969:Molecular Sequence Data; D010053:Ovary / Q000254:growth & development; D010641:Phenotype; D017354:Point Mutation / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D019849:Sex Determination Processes; D014157:Transcription Factors / Q000235:genetics*; D016335:Zinc Fingers
D018387:Codon, Initiator; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C089512:ovo protein, Drosophila