Role of 2',5'-oligo(adenylic acid) polymerase in the degradation of ribonucleic acid linked to double-stranded ribonucleic acid by extracts of interferon-treated cells

RNA covalently linked to double-stranded RNA (dsRNA) is preferentially degraded in extracts of interferon-treated HeLa cells [Nilsen, T. W., & Baglioni, C. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 2600-2604]. The size of the dsRNA required for this preferential degradation has been determined by annealing poly(I) of known length to the poly(C) tract of encephalomyocarditis virus (EMCV) RNA or by annealing poly(U) to poly(A) of known length of vesicular stomatitis virus mRNA. The dsRNA must be longer than about 60 base pairs to observe the preferential degradation of RNA. Moreover, triple-stranded regions that do not activate synthesis of 2',5'-oligo(A) and ethidium bromide, which intercalates in dsRNA and blocks 2',5'-olido(A) polymerase activation, prevent this degradation. Ethidium also blocks the degradation of the replicative intermediate of EMCV by extracts of interferon-treated cells. These experiments indicate that synthesis of 2',5'-oligo(A) is required for the degradation of RNA linked to dsRNA. The 2',5'-oligo(A)-dependent endonuclease does not cleave single- or double-stranded DNA, nor does it cleave homopolyribonucleotides. The potential role of the 2',5'-oligo(A) polymerase/endonuclease system in the inhibition of viral RNA replication is discussed.     

Cell surface expression and alloantigenic function of a human class I MHC heavy chain gene (HLA-B7) in transgenic mice

We have introduced the gene encoding the heavy chain of the human MHC class I Ag HLA-B7 into transgenic mice. The gene was shown to be expressed at both the RNA and protein level. Cell surface HLA-B7 was detected on whole spleen cells by immunoprecipitation and on purified T cells by flow cytometry (FACS). Normal mice immunized with H-2-syngeneic B7-transgenic spleen cells generated CTL capable of killing transgenic cells and B7-expressing human JY cells. Anti-HLA mAb blocked the killing of JY cells. These results indicate that the human class I Ag HLA-B7 can be expressed at the surface of transgenic spleen cells in the absence of human beta 2-microglobulin, and that a significant fraction exists in a form recognizable by nontransgenic CTL as a major histocompatibility Ag unrestricted by H-2.     

Genome-wide programmable transcriptional memory by CRISPR-based epigenome editing

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Renal calcium binding protein in the diabetic and vitamin D-depleted rat.

A calcium binding protein has been purified 220 fold from rat kidney. The molecular weight of this protein (26 000-28 000) is more than double that of the duodenal calcium binding protein of the rat. In response to the stimuli of both streptozotocin diabetes and depletion and repletion with vitamin D, changes in the renal protein are minimal. This contrasts markedly with responses of the duodenal protein to the same stimuli: (a) there was marked depression of duodenal calcium binding protein by vitamin D depletion and diabetes; (b) duodenal calcium binding protein was restored by vitamin D treatment of depleted rats. The renal protein appears to be identical with a previously described 28 000 molecular weight protein from the kidney purified by a different technique (Hermsdorf, C.L. and Bronner, F. (1975) Biochim. Biophys. Acta 379, 553-561). In contrast to findings of the current study, previous investigators were unable to isolate the protein from vitamin D-deficient rats and postulated vitamin D dependence. The protein activator of cyclic AMP phosphodiesterase is a calcium binding protein found in many tissues including kidney. Based on lack of response to stimuli we used and similarity in method of isolation and properties, our renal calcium binding protein may be this protein activator.     

The pro region of BPTI facilitates folding.

The in vitro folding pathway of bovine pancreatic trypsin inhibitor (BPTI) has been described previously in terms of the disulfide-bonded intermediates that accumulate during folding of the protein. Folding is slow, occurring in hours at pH 7.3, 25 degrees C. In addition, approximately half of the BPTI molecules become trapped as a dead-end, native-like intermediate. In vivo, BPTI is synthesized as a precursor protein that includes a 13 residue amino-terminal pro region. This pro region contains a cysteine residue. We find that, in vitro, both the rate of formation and the yield of properly folded BPTI are increased substantially in a recombinant model of pro-BPTI. The cysteine residue is necessary for this effect. Moreover, a single cysteine residue, tethered to the carboxy-terminal end of BPTI with a flexible linker of repeating Ser-Gly-Gly residues, is sufficient to assist in disulfide formation. Thus, the pro region appears to facilitate folding by providing a tethered, solvent-accessible, intramolecular thiol-disulfide reagent.