ABSTRACT
The lin-31 gene is required for the proper specification of vulval cell fates in the nematode Caenorhabditis elegans and encodes a member of the winged-helix family of transcription factors. Members of this important family have been identified in many organisms and are known to bind specific DNA targets involved in a variety of developmental processes. DNA sequencing of 13 lin-31 alleles revealed six nonsense mutations and two missense mutations within the DNA-binding domain, plus three deletions, one transposon insertion, and one frameshift mutation that all cause large-scale disruptions in the gene. The missense mutations are amino acid substitutions in the DNA-binding domain and probably disrupt interactions of the LIN-31 transcription factor with its DNA target. In addition, detailed phenotypic analysis of all 19 alleles showed similar penetrance for several characteristics examined. From our analysis we conclude: (1) the null phenotype of lin-31 is the phenotype displayed by almost all of the existing alleles, (2) the DNA-binding domain plays a critical role in LIN-31 function, and (3) direct screens for multivulva and vulvaless mutants will probably yield only null (or strong) alleles of lin-31.
Subject(s)
Caenorhabditis elegans Proteins , Caenorhabditis elegans/genetics , DNA-Binding Proteins/genetics , Genes, Helminth , Helminth Proteins/genetics , Transcription Factors/genetics , Vulva/embryology , Alleles , Amino Acid Sequence , Amino Acid Substitution , Animals , Binding Sites , Caenorhabditis elegans/embryology , Codon, Nonsense , DNA Mutational Analysis , DNA, Helminth/genetics , DNA, Helminth/metabolism , DNA-Binding Proteins/physiology , Disorders of Sex Development , Female , Helminth Proteins/physiology , Male , Molecular Sequence Data , Morphogenesis , Multigene Family , Mutation, Missense , Phenotype , Protein Structure, Tertiary , Sequence Alignment , Sequence Deletion , Sequence Homology, Amino Acid , Transcription Factors/physiology , Vulva/abnormalities , Vulva/cytologyABSTRACT
The human beta-globin locus control region (LCR), which consists of four erythroid-specific DNase I hypersensitive sites (HS1-HS4), functions over a long distance to control the transcription, chromatin structure, and replication of the beta-globin genes. We have used stable transfection assays to show that activation of the mitogen-activated protein (MAP) kinase pathway by low concentrations of the phorbol ester phorbol 12-tetradecanoate 13-acetate (TPA) induces enhancer activity of the LCR subregion HS2, but not HS3. Although HS2 enhancer activity is diminished with increasing distance from the promoter, the relative level of induction by TPA is independent of HS2-promoter distance. Mutation of cis-elements within HS2 reveals that the tandem-binding sites for the hematopoietic-specific transcription factor NF-E2 are required for induction by TPA, and induction is conferred by expressing NF-E2 in an NF-E2-null cell line. These results show that MAP kinases target factors functioning through the NF-E2 sites to enhance long-range transactivation by the LCR.