The mouse homolog of the human amyloid beta protein (AD-AP) gene is located on the distal end of mouse chromosome 16: further extension of the homology between human chromosome 21 and mouse chromosome 16

The human amyloid beta protein is the major constituent of the brain amyloid plaques found in Alzheimer disease. The gene that encodes this protein is located on chromosome 21, and individuals with Down syndrome (trisomy 21) also exhibit an early onset form of Alzheimer disease. We have used the cloned human amyloid beta protein gene and a panel of somatic cell hybrids to map the location of the mouse homolog of this gene. We report here that the mouse gene is located on chromosome 16 within the region 16C3----ter, in common with three other genes which map within the Down syndrome region of human chromosome 21.     

Oxygen concentration profiles and exchange in sediment cores with circulated overlying water

SUMMARY. 1. The overlying water of intact sediment cores was constantly stirred with an impeller at a rate sufficient to mix turbulently the water column and maintain the diffusive boundary layer at a determined thickness. The system allowed standardization of water circulation in laboratory sediment core experiments.
2. Both oxygen concentration and oxygen penetration depth in the sediments decreased, the former by 70% and the latter from 4.2 mm to 2.0 mm, when the overlying water was not stirred for 24 h, as measured with oxygen microelectrodes in a lake sediment core.
3. Oxygen profiles measured in sediment cores in the laboratory were similar to those measured in situ when the overlying water was stirred with an impeller at such a rate that a similar thickness of the diffusive boundary layer at the sediment-water interface developed in the laboratory as that in situ.
4. Sediment oxygen consumption was calculated from: (1) measured oxygen profiles in the diffusive boundary layer and the molecular diffusion coefficient for oxygen in water; (2) the measured oxygen decrease in the top of the sediments and the estimated diffusion coefficient in the sediment; and (3) by oxygen differences in the overlying water after incubation of sediment cores.     

Characterization of the interleukin-1-induced tyrosine phosphorylation of a 41-kDa plasma membrane protein of the human tumor cell line K 562

A 41-kDa protein, which was specifically phosphorylated upon incubation with natural purified murine interleukin 1, was recently identified by us [Martin, M., Lovett, D. H. and Resch, K. (1986) Immunobiology 171, 165-169] in highly purified plasma membranes from the human tumor cell line K 562. An in vitro assay was used to investigate and characterize the phosphorylation induced by interleukin 1, possibly involved in signal transduction and generation. Plasma membranes were incubated with radiolabeled ATP in the presence of purified natural murine interleukin 1, or recombinant human interleukin 1 alpha and the pattern of phosphoproteins was studied after separation by SDS/PAGE and subsequent autoradiography. A 41-kDa protein (pp41) was specifically phosphorylated on a tyrosine residue in the presence of interleukin 1 in a dose- and time-dependent manner. The protein showed a weak background phosphorylation in the absence of monokine. Phosphorylation took place very efficiently at 0 degrees C, whereas phosphatases were not active at that temperature. At 37 degrees C, a rapid dephosphorylation was observed which was inhibited specifically by Zn2+ and vanadate. The interleukin-1-specific induction of the phosphorylation could also be observed after detergent solubilization of the plasma membranes. Affinity labeling with an ATP analogue revealed an ATP-binding and cleaving site at 41 kDa. Interleukin 1 did not induce the phosphorylation of p41 in plasma membranes obtained from a subclone of K 562, which did not respond to interleukin 1 with growth inhibition, as was reported recently for the K 562 mother line [Lovett, D. H., Kozan, B., Hadam, M., Resch, K. and Gemsa, D. (1986) J. Immunol. 136, 340-347]. These data suggest that the interleukin-1 receptor is functionally linked to a protein-tyrosine kinase, which is implicated in its biological function.     

Site in the cat-86 regulatory leader that permits amicetin to induce expression of the gene.

Expression of the plasmid gene cat-86 is induced in Bacillus subtilis by two antibiotics, chloramphenicol and the nucleoside antibiotic amicetin. We proposed that induction by either drug causes the destabilization of a stem-loop structure in cat-86 mRNA that sequesters the ribosome-binding site for the cat coding sequence. The destabilization event frees the ribosome-binding site, permitting the initiation of translation of cat-86 mRNA. cat-86 induction is due to the stalling of a ribosome in a leader region of cat-86 mRNA, which is located 5' to the RNA stem-loop structure. A stalled ribosome that is active in cat-86 induction has its aminoacyl site occupied by leader codon 6. To test the hypothesis that a leader site 5' to codon 6 permits a ribosome to stall in the presence of an inducing antibiotic, we inserted an extra codon between leader codons 5 and 6. This insertion blocked induction, which was then restored by the deletion of leader codon 6. Thus, induction seems to require the maintenance of a precise spatial relationship between an upstream leader site(s) and leader codon 6. Mutations in the ribosome-binding site for the cat-86 leader, RBS-2, which decreased its strength of binding to 16S rRNA, prevented induction. In contrast, mutations that significantly altered the sequence of RBS-2 but increased its strength of binding to 16S rRNA did not block induction by either chloramphenicol or amicetin. We therefore suspected that the proposed leader site that permitted drug-mediated stalling was located between RBS-2 and leader codon 6. This region of the cat-86 leader contains an eight-nucleotide sequence (conserved region I) that is largely conserved among all known cat leaders. The codon immediately 5' to conserved region I differs, however, between amicetin-inducible and amicetin-noninducible cat genes. In amicetin-inducible cat genes such as cat-86, the codon 5' to conserved region I is a valine codon, GTG. The same codon in amicetin-noninducible cat genes is a lysine codon, either AAA or AAG. When the GTG codon immediately 5' to conserved region I in cat-86 was changed to AAA, amicetin was no longer active in cat-86 induction, but chloramphenicol induction was unaffected by the mutation. The potential role of the GTG codon in amicetin induction is discussed.     

SOS-like induction in Bacillus subtilis: induction of the RecA protein analog and a damage-inducible operon by DNA damage in Rec+ and DNA repair-deficient strains.

We quantitated the induction of the Bacillus subtilis Rec protein (the analog of Escherichia coli RecA protein) and the B. subtilis din-22 operon (representative of a set of DNA damage-inducible operons in B. subtilis) following DNA damage in Rec+ and DNA repair-deficient strains. After exposure to mitomycin C or UV irradiation, each of four distinct rec (recA1, recB2, recE4, and recM13) mutations reduced to the same extent the rates of both Rec protein induction (determined by densitometric scanning of immunoblot transfers) and din-22 operon induction (determined by assaying beta-galactosidase activity in din-22::Tn917-lacZ fusion strains). The induction deficiencies in recA1 and recE4 strains were partially complemented by the E. coli RecA protein, which was expressed on a plasmid in B. subtilis; the E. coli RecA protein had no effect on either induction event in Rec+, recB2, or recM13 strains. These results suggest that (i) the expression of both the B. subtilis Rec protein and the din-22 operon share a common regulatory component, (ii) the recA1 and recE4 mutations affect the regulation and/or activity of the B. subtilis Rec protein, and (iii) an SOS regulatory system like the E. coli system is highly conserved in B. subtilis. We also showed that the basal level of B. subtilis Rec protein is about 4,500 molecules per cell and that maximum induction by DNA damage causes an approximately fivefold increase in the rate of Rec protein accumulation.     

Correlation of treponemicidal activity in normal human serum with the presence of IgG antibody directed against polypeptides of Treponema phagedenis biotype Reiter and Treponema pallidum, Nichols strain

Normal human serum (NHS) was shown to have complement-dependent treponemicidal activity against both Treponema pallidum and Treponema phagedenis biotype Reiter (TPR) by employing in vitro-in vivo neutralization and TPR plaque assays, respectively. The molecular basis of NHS treponemicidal activity was studied by immunoblot analysis in conjunction with treponemicidal assays. Five major T. pallidum polypeptide bands (47kDa, 35kDa, 33kDa doublet, and 30 kDa) and three major TPR polypeptide bands (47kDa and 33kDa doublet) bound IgG present in NHS. Absorption of NHS with TPR completely removed both TPR and T. pallidum treponemicidal activity; corresponding immunoblots demonstrated a significant removal of IgG antibody against all three TPR polypeptide bands as well as four T. pallidum polypeptide bands (30kDa, 33kDa doublet, and 35kDa). In contrast, T. pallidum absorption of NHS was found to remove treponemicidal activity against T. pallidum but not TPR; corresponding Western blots showed the complete removal of IgG antibody against all but one T. pallidum polypeptide band (47kDa) but no detectable loss in IgG antibody against the TPR polypeptides. These results suggest that antibody in NHS generated against nonpathogenic, indigenous treponemes is responsible for the T. pallidum treponemicidal activity. Furthermore, the treponemicidal activity against T. pallidum correlated with the presence of IgG antibody against T. pallidum polypeptides of 30kDa, 35kDa, and a 33kDa doublet.     

Analysis of the regulatory sequences needed for induction of the chloramphenicol acetyltransferase gene cat-86 by chloramphenicol and amicetin.

Induction of the chloramphenicol acetyltransferase gene cat-86 in Bacillus subtilis results from the activation of translation of cat-86 mRNA. The inducers, chloramphenicol and amicetin, are thought to enable ribosomes to destabilize a stem-loop structure in cat-86 mRNA that sequesters the ribosome binding site for the cat-86 coding sequence, designated RBS-3. The region of cat-86 mRNA which is 5' to the stem-loop contained two additional ribosome binding sites, RBS-1 and RBS-2, located 84 and 56 nucleotides, respectively, upstream from RBS-3. RBS-1 and RBS-2 were each followed by a potential translation initiation codon and a short open reading frame. Bal 31-generated deletions into the 5' end of the regulatory region that removed RBS-1 but did not enter RBS-2 caused a fourfold decrease in the uninduced and chloramphenicol-induced level of cat-86 expression and a more than 10-fold reduction in the amicetin-induced level of expression. Deletions that removed both RBS-1 and RBS-2 but did not enter the stem-loop abolished both chloramphenicol- and amicetin-inducible expression. These data indicate that RBS-2 and sequences 3' to RBS-2 are minimally essential to chloramphenicol induction. However, the presence of RBS-1 in the mRNA elevated the maximum level of expression obtained during chloramphenicol induction. These studies also demonstrate that induction of cat-86 by amicetin is highly dependent on RBS-1. To determine whether a correlation existed between RBS-1 and amicetin inducibility, we examined the sequence of the regulatory regions for two natural variants of cat-86, cat-66 and cat-57, which are chloramphenicol inducible but are very poorly induced by amicetin. Both contained nucleotide sequence differences from cat-86 in the vicinity of RBS-1 that would prevent translation of the leader peptide associated with RBS-1 in cat-86. In contrast, the regulatory regions got the three genes were virtually identical in the vicinity of RBS-2. These data indicate that efficient induction by amicetin requires sequences that are not essential for induction by chloramphenicol.