Novel cysteine-rich motif and homeodomain in the product of the Caenorhabditis elegans cell lineage gene lin-11

The unc-86 gene product couples cell lineage and cell identity in C. elegans

The C. elegans gene unc-86 is required in several distinct neuroblast lineages for daughter cells to become different from their mothers, and is also required for the specification of particular neural identities. Consistent with the fact that unc-86 encodes a POU domain protein, we find that the unc-86 protein is localized to the nucleus. In the affected lineages, unc-86 protein appears within a few minutes after cell division in the nuclei of those daughter cells that are transformed by unc-86 mutations. Thus, expression of unc-86 protein is dependent on cell lineage. unc-86 protein is not asymmetrically segregated at further divisions. unc-86 protein also appears shortly after cell division in the nuclei of particular identified differentiating neurons; at least some of these neurons are nonfunctional in unc-86 mutants.

A TaqI RFLP for the human arylsulfatase A gene

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Homeobox containing genes in the nematode Caenorhabditis elegans

We designed a unique 36-mer oligonucleotide probe, based on the most highly conserved amino acid sequences of Antennapedia-like homeodomains and the codon bias of Caenorhabditis elegans. This probe was then used to isolate four classes of genes from a C. elegans genomic library. Sequencing reveals that we have isolated three new homeobox genes, designated ceh-1, ceh-9 and ceh-10. The fourth homeobox gene, ceh-11, has recently been described by Schaller et al (Nucleic Acids Res. 18, 2033-2036). The amino acid sequence of ceh-1 is 87% similar to the honeybee H40 homeodomain, 85% similar to the Drosophila NK-1 homeodomain and 82% similar to the chicken CHox3 homeodomain. The sequence ceh-10 appears to be a member of the paired class of homeodomains. The other two sequences, ceh-9 and ceh-11, remain unclassified. Three of the four sequences have at least one intron within the homeobox region. Transcripts of ceh-10 and ceh-11 are present in embryonic RNA but are greatly diminished in later developmental stages. Three of the four new genes have been placed on the C. elegans genomic map.

cDNA sequence analysis of a 29-kDa cysteine-rich surface antigen of pathogenic Entamoeba histolytica

A gamma gt11 cDNA library was constructed from poly(U)-Sepharose-selected Entamoeba histolytica trophozoite RNA in order to clone and identify surface antigens. The library was screened with rabbit polyclonal anti-E. histolytica serum. A 700-base-pair cDNA insert was isolated and the nucleotide sequence was determined. The deduced amino acid sequence of the cDNA revealed a cysteine-rich protein. DNA hybridizations showed that the gene was specific to E. histolytica since the cDNA probe reacted with DNA from four axenic strains of E. histolytica but did not react with DNA from Entamoeba invadens, Acanthamoeba castellanii, or Trichomonas vaginalis. The insert was subcloned into the expression vector pGEX-1 and the protein was expressed as a fusion with the C terminus of glutathione S-transferase. Purified fusion protein was used to generate 22 monoclonal antibodies (mAbs) and a mouse polyclonal antiserum specific for the E. histolytica portion of the fusion protein. A 29-kDa protein was identified as a surface antigen when mAbs were used to immunoprecipitate the antigen from metabolically 35S-labeled live trophozoites. The surface location of the antigen was corroborated by mAb immunoprecipitation of a 29-kDa protein from surface-125I-labeled whole trophozoites as well as by the reaction of mAbs with live trophozoites in an indirect immunofluorescence assay performed at 4 degrees C. Immunoblotting with mAbs demonstrated that the antigen was present on four axenic isolates tested. mAbs recognized epitopes on the 29-kDa native antigen on some but not all clinical isolates tested.

Two human TNF receptors have similar extracellular, but distinct intracellular, domain sequences

Tumor necrosis factor (TNF) is a cytokine with a wide range of biological activities in inflammatory and immunologic responses. These activities are mediated by specific cell surface receptors of 55 kDa and 75 kDa apparent molecular masses. A 75-kDa TNF receptor cDNA was isolated using partial amino acid sequence information and the polymerase chain reaction (PCR). When expressed in COS-1 cells, the cDNA transfers specific TNF-binding properties comparable to those of the native receptor. The predicted extracellular region contains four domains with characteristic cysteine residues highly similar to those of the 55-kDa TNF receptor, the nerve growth factor (NGF) receptor, and the CDw40 and OX40 antigens. The consensus sequence of the TNF receptor extracellular domains also has similarity to the cysteine-rich sequence motif LIM. In marked contrast to the extracellular regions, the intracellular domains of the two TNF receptors are entirely unrelated, suggesting different modes of signaling and function.

Insulin gene enhancer binding protein Isl-1 is a member of a novel class of proteins containing both a homeo- and a Cys-His domain

The activity of the rat insulin I gene enhancer is mainly dependent on two cis-acting protein-binding domains. Here we report the isolation of a complementary DNA encoding a protein, Isl-1, that binds to one of these domains. Isl-1 contains a homeodomain with greatest similarity to those of the Caenorhabditis elegans proteins encoded by mec-3 and lin-11. In addition, Isl-1, like the lin-11 and mec-3 gene products, contains a novel Cys-His domain which is reminiscent of known metal-binding regions. Together these proteins define a novel class of proteins containing both a homeo- and a Cys His-domain. Isl-1 is preferentially expressed in cells of pancreatic endocrine origin. If the structural homologies between Isl-1 and the C. elegans gene products reflect functional similarities, a role for Isl-1 in the development of pancreatic endocrine cells could be envisaged.