ARMER,apoptotic regulator in the membrane of the endoplasmic reticulum,a novel inhibitor of apoptosis

We have identified a novel protein, apoptotic regulator in the membrane of the endoplasmic reticulum (ARMER), which protects HT1080 fibrosarcoma cells from apoptosis induced by various stimuli. We demonstrate that ARMER is an endoplasmic reticulum (ER) integral membrane protein with four predicted transmembrane domains and a COOH-terminal KKXX ER retrieval motif. We used an inducible expression system (pIND) to study the effects of regulated ARMER overexpression. Cells in which ARMER was overexpressed exhibited protection from multiple apoptotic inducers including serum starvation, doxorubicin, UV irradiation, tumor necrosis factor alpha, and the ER stressors brefeldin A, tunicamycin, and thapsigargin. Analysis of the caspase proteolytic cascade reveals that ARMER inhibits proteolysis of the caspase-9-specific fluorogenic substrate LEHD-AFC as well as endogenous substrates downstream of caspase-9; however, it does not inhibit cytochrome c release or cleavage of caspase-9 itself. Apoptotic stimuli cause endogenous levels of ARMER protein and RNA to decrease, leading to cell death; however, sustaining ARMER protein levels through exogenous expression inhibits apoptosis. These data suggest that ARMER is a novel ER integral membrane protein which protects cells by inhibiting caspase-9 activity and reveal a possible role for ARMER in cell survival.     

Mitochondrial gene order is not conserved in arthropods: prostriate and metastriate tick mitochondrial genomes

The entire mitochondrial genome was sequenced in a prostriate tick, Ixodes hexagonus, and a metastriate tick, Rhipicephalus sanguineus. Both genomes encode 22 tRNAs, 13 proteins, and two ribosomal RNAs. Prostriate ticks are basal members of Ixodidae and have the same gene order as Limulus polyphemus. In contrast, in R. sanguineus, a block of genes encoding NADH dehydrogenase subunit 1 (ND1), tRNA(Leu)(UUR), tRNA(Leu)(CUN), 16S rDNA, tRNA(Val), 12S rDNA, the control region, and the tRNA(Ile) and tRNA(Gln) have translocated to a position between the tRNA(Glu) and tRNA(Phe) genes. The tRNA(Cys) gene has translocated between the control region and the tRNA(Met) gene, and the tRNA(Leu)(CUN) gene has translocated between the tRNA(Ser)(UCN) gene and the control region. Furthermore, the control region is duplicated, and both copies undergo concerted evolution. Primers that flank these rearrangements confirm that this gene order is conserved in all metastriate ticks examined. Correspondence analysis of amino acid and codon use in the two ticks and in nine other arthropod mitochondrial genomes indicate a strong bias in R. sanguineus towards amino acids encoded by AT-rich codons.      

Density-dependent selection migration model with non-monotone fitness functions

This paper studies the classical single locus, diallelic selection model with diffusion for a continuously reproducing population. The phase variables are population density and allele frequency (or allele density). The genotype fitness depend only on population density but include one-hump functions of the density variable. With mild assumptions on genotype fitnesses, we study the geometry of the nullclines and the asymptotic behavior of solutions of the selection model without diffusion. For the diffusion model with zero Neumann boundary conditions, we use this geometric information to show that if the initial data satisfy certain conditions then the corresponding solution to the reaction-diffusion equation converges to the spatially constant stable equilibrium which is closest to the initial data.Research partially supported by NSF grant DMS-8920597Research supported by funds provided by the USDA-Forest Service, Southeastern Forest Experiment Station, Pioneering (Population Genetics of Forest Trees) Research Unit, Raleigh, North Carolina     

Procedures for obtaining high percentages of viable in vitro capacitated hamster sperm

Suspensions of nearly 100% viable golden hamster sperm were prepared by passing washed cauda epididymal sperm through a column of 0.25–0.3 mm glass beads. Incubations of these viable sperm under in vitro capacitation conditions in volumes of 0.1 or 1 ml (2–2.5 × 10⁶/ml) resulted in 85–92% viable sperm after four hours and 45 minutes of incubation. More than 70% of these sperm were judged to have been capacitated after four hours and 45 minutes of incubation on the basis of their having undergone acrosome reactions and the presence of high numbers of sperm exhibiting the activated motility characteristic of capacitated hamster sperm. Thus, for the first time, procedures are available that will yield large numbers of viable capacitated sperm for biochemical analysis and that will also allow other studies of hamster sperm capacitation with minimum interference from molecules released from dead sperm.     

Partial reactions of aminoacyl-tRNA synthetases as functions of pH.

The effect of pH on the properties of the partial reactions of arginyl-tRNA synthetase of E. coli has been investigated. V max of pyrophosphorolysis of arginyl adenylate has a pH optimum at pH 6.1, whereas V max of the transfer of arginine to tRNA has a pH optimum of 8.2. These values correlate with the pH optima of the ATP:PPi exchange and the overall esterification reaction, respectively. Only the pyrophosphorolysis reaction requires a divalent cation; transfer proceeds in the presence of EDTA. Inorganic pyrophosphate inhibits the transfer reaction to an extent independent of the concentration of tRNA; the maximum inhibition is a function of pH, corresponding to the relative rate of pyrophosphorolysis of the common intermediate compared with the rate of transfer. These results show that different groups on the enzyme participate in the rate-limiting steps of the two partial reactions and that these partial reactions have properties consistent with their participation in the overall esterification of arginine with tRNA.     

Nucleotide sequence of a mouse kappa light chain cDNA cloned in a bacterial plasmid.

A mouse MOPC21 cDNA previously cloned in plasmid pMB9(Higuchi $\text{et}\text{al.}$, Proc. Natl. Acad. Sci. 73 (1976) 2136–2140; Wall $\text{et}\text{al.}$, Nucleic Acid Res. 5 (1978) 3113–3128) and is designated pL21-3 has been extensively characterized. Cleavage of pL21-3 with Hpall has shown the insert to be 910 basepairs long, consistent with the length of the entire variable and constant regions and the untranslated regions. Digestion of pL21-3 with various restriction endonucleases has established that the insert sequence starts from parts of the 5′ leader region and extends downstream to include the untranslated 3′ terminus. 131 nucleotides in the variable region corresponding to amino acids 49–91 have been determined.     

Tests of Homogeneity for the Relative Difference between Strata under Inverse Sampling

This paper develops the exact and asymptotic test procedures for detecting whether the relative difference of a given disease between exposure and non-exposure to a risk factor varies between strata under inverse sampling. This paper applies Monte Carlo Simulation to evaluate the performance of the proposed asymptotic test procedures and further demonstrates that these asymptotic procedures can be useful in many situations, especially when either the number of index subjects is large or the probability of possessing the underlying disease is small.