RESUMO
The par-2 gene of Caenorhabditis elegans functions in early embryogenesis to ensure an asymmetric first cleavage and the segregation of cytoplasmic factors. Both processes appear to be required to generate daughter blastomeres with distinct developmental potential. We isolated an allele of par-2 by using a screen for maternal-effect lethal mutations in a strain known for its high frequency of transposition events. A transposable element was found to be linked to this allele. Sequences flanking the site of transposon insertion were cloned and found to rescue the par-2 mutant phenotype. DNA in the par-2 region hybridized to a 2.3-kb germ-line-enriched mRNA. The cDNA corresponding to this germ-line-enriched message was cloned, sequenced, and used to identify the molecular lesions associated with three par-2 alleles. Sequence analysis of the par-2 cDNA revealed that the predicted protein contained two distinct motifs found in other known proteins: an ATP-binding site and a cysteine-rich motif which identifies the par-2 gene product as a member of a growing class of putative zinc-binding proteins.
Assuntos
Trifosfato de Adenosina/metabolismo , Blastômeros/fisiologia , Proteínas de Caenorhabditis elegans , Caenorhabditis elegans/genética , Proteínas de Helminto/biossíntese , Dedos de Zinco/genética , Alelos , Sequência de Aminoácidos , Animais , Sequência de Bases , Sítios de Ligação , Northern Blotting , Southern Blotting , Caenorhabditis elegans/embriologia , Cromossomos Artificiais de Levedura , Clonagem Molecular , Sequência Consenso , DNA/análise , DNA/metabolismo , Primers do DNA , Embrião não Mamífero/fisiologia , Proteínas de Helminto/genética , Humanos , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Polimorfismo Genético , RNA Mensageiro/biossíntese , RNA Mensageiro/metabolismo , Mapeamento por Restrição , Homologia de Sequência de AminoácidosRESUMO
Nucleotide sequence analysis revealed that a DNA length polymorphism 5' to the human antithrombin III gene is due to the presence of 32bp or 108bp nonhomologous nucleotide sequences (variable segments) 345bp upstream from the translation initiation codon. Sequences at the 3' borders of both variable segments can form intrastrand inverted repeat structures with sequences further downstream. An inverted repeat is also found immediately 5' to the site where the variable segments are located. Thus, cruciform structures may form flanking the variable segments of both alleles of this DNA length polymorphism. DNA secondary structure may be detected with single strand specific nucleases. S1 nuclease sensitive sites were mapped in recombinant plasmids containing the cloned alleles of the ATIII length polymorphism. The site most sensitive to S1 is located upstream from the variable segments in an AT-rich segment flanked by 6bp direct repeats. A region of lesser nuclease sensitivity was also observed in the AT-rich loops formed between the inverted repeats 5' to the variable segments.
