title: Induction of heat-stable enterotoxin receptor activity by a human Alu repeat.
abstract: The heat-stable enterotoxins (ST) elaborated by enterotoxigenic Escherichia coli are a family of small cysteine-rich peptides that bind to specific epithelial receptors in the mammalian intestine, causing a secretory diarrhea. The expression of ST receptors is tightly regulated; they are found primarily in intestine, and their expression is developmentally modulated. One receptor for ST has been cloned, and its cDNA encodes a approximately 120-kDa particulate guanylyl cyclase (guanylyl cyclase-C). Recent studies suggest that there are additional ST receptors that are not homologous to guanylyl cyclase-C. We used an expression cloning strategy to identify intestinal mRNAs that lead to expression of ST receptor activity in transfected cells. Using an ST-specific affinity panning system, we identified a novel 1891-base pair cDNA that does not encode a receptor protein, but instead, consists primarily of untranslated sequence. This cDNA induced receptor activity in both COS and 293 embryonic kidney cells. Northern analysis of the T84 human intestinal cell line, from which this cDNA was cloned, suggests that it is part of a 7.8-kilobase mRNA transcript. This transcript was also identified in human small intestine and colon, as well as in several extra-intestinal tissues. Functional analysis of subcloned fragments reveals that ST binding activity is induced by a 457-base pair human Alu repetitive sequence within the cDNA and that the phenotype is independent of orientation. These findings suggest that a human Alu element induces expression of a unique ST receptor by a transacting mechanism. An unrelated Alu-rich genomic clone did not confer ST binding, suggesting that there may be structural and functional specificity within individual Alu sequences.
authors.affiliation: Howard Hughes Medical Institute, Stanford University Medical Center, California 94305.
authors.forename: J S
authors.initials: JS
authors.lastname: Almenoff
authors.forename: J
authors.initials: J
authors.lastname: Jurka
authors.forename: G K
authors.initials: GK
authors.lastname: Schoolnik
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002460:Cell Line; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D003110:Colonic Neoplasms; D017931:DNA Primers; D018076:DNA, Complementary / Q000032:analysis / Q000378:metabolism; D004768:Enterotoxins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D005260:Female; D015723:Gene Library; D006162:Guanylate Cyclase; D006801:Humans; D007668:Kidney; D008297:Male; D008969:Molecular Sequence Data; D009928:Organ Specificity; D016133:Polymerase Chain Reaction; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000096:biosynthesis; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D001427:Bacterial Toxins; D017931:DNA Primers; D018076:DNA, Complementary; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D018000:Receptors, Peptide; D011994:Recombinant Proteins; C034151:heat stable toxin (E coli); D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled