Multiple mRNA species for adenovirus type 2 polypeptides III and pVII.

Fractionation of messenger activities isolated from the cytoplasm of HeLa cells late in infection with adenovirus type 2 reveals that viral polypeptides III and pVII are each synthesized from two different-sized mRNA's. the major messenger activity for each protein has the same sedimentation rate as that previously reported by Anderson et al. (Proc. Natl. Acad. Sci. U.S.A. 71:2756-2760, 1974). The minor messenger activities for III and pVII sediment more rapidly and are not aggregates of the major mRNA's for these proteins. The two minor messenger activities cosediment with two polyadenylated RNA species which are labeled late in infection with 32P and whose molecular weights are estimated to be 2.9 x 10(6) and 2.4 x 10(6). Both of these species hybridize to adenovirus type 2 DNA specific for the mRNA family that is 3' coterminal at adenovirus type 2 map position 49.5 and the mRNA family that is 3' coterminal at 62.0. This is consistent with the possibility that these RNAs have 5'-terminal sequences identical to those of the normal mRNA's for III and pVII but are 3' coterminal at map position 62, the normal 3' terminus of the mRNA's for polypeptides II and pVI. These species are not found in polyadenylated RNA isolated from the nucleus, suggesting that the minor mRNA species are cytoplasmic RNAs.     

The araC regulatory gene mRNA contains a leader sequence

Summary An estimation of the size of the araC gene in Escherichia coli B/r was made by sub-cloning restriction fragments of the araC-containing hybrid plasmid pTB1 into the plasmid pBR322. Plasmids which contained a functional araC gene were identified by genetic complementation tests. DNA sequence analysis of the promoter-proximal region of the araC gene revealed that araC mRNA contains a 150 nucleotide leader.     

Cell-free synthesis of glial fibrillary acidic protein

Glial fibrillary acidic (GFA) protein has been synthesized in an RNA-dependent cell-free system derived from rabbit reticulocytes. The cell-free synthesized product appears to have the same size as GFA protein isolated from bovine spinal cord, thus showing that GFA protein does not undergo detectable proteolytic processing.     

Histone acetylation and heterochromatin content of cultured Peromyscus cells

In order to explore the relationship between unacetylated arginine-rich histones and condensed chromatin structure, the extent of histone acetylation was examined in cultured cell lines derived from three species of deer mice. These species differ considerably in their genomic content of heterochromatin but contain essentially the same euchromatin content. Cells of Peromyscus eremicus, containing 34–36% more constitutive heterochromatin than Peromyscus boylii or Peromyscus crinitus cells were found to contain 28–35% more unacetylated histone H4, 22–29% more unacetylated histone H3, and 18–22% more unacetylated histone H2B. This relationship between unacetylated histones and heterochromatin content was further explored by inducing hyperacetylation of P. eremicus and P. boylii histones through treatment of cells with 15 mM sodium butyrate for 24 h. It was found that the percentages of unacetylated histones H3 and H4 remaining after butyrate treatment were proportional to the amount of constitutive heterochromatin in the genome. These data support the concept that a small core of histones in constitutive heterochromatin is inaccessible to acetylation. It was also found that the acetylated state of isolated histones was sensitive to the method of histone extraction. Thus concern must be given to preparative procedures when studying histone acetylation in order to minimize these acetate losses.     

Echinococcus granulosus cysts: Early development in vitro in the presence of serum from infected sheep

When cultured in vitro in the presence of serum from a number of sheep infected with Echinococcus granulosus cysts, varying proportions of oncospheres died within 24 h. Of the survivors, some died during reorganization into cysts; others were able to develop normally but showed evidence of precipitates in the outer layers of the cyst. The lethal effects were removed by heating the serum to 56°C for 30 min and could be restored by the addition of freshly-collected normal sheep serum. In the presence of serum from sheep immunized against E. granulosus, most oncospheres were dead within 24 h, and few or none of the survivors were able to reorganize into cysts.     

Tetrodotoxin-insensitive sodium channels. Binding of polypeptide neurotoxins in primary cultures of rat muscle cells

The binding of 125I-labeled derivatives of scorpion toxin and sea anemone toxin to tetrodotoxin-insensitive sodium channels in cultured rat muscle cells has been studied. Specific binding of 125I-labeled scorpion toxin and 125I-labeled sea anemone toxin was each blocked by either native scorpion toxin or native sea anemone toxin. K0.5 for block of binding by several polypeptide toxins was closely correlated with K0.5 for enhancement of sodium channel activation in rat muscle cells. These results directly demonstrate binding of sea anemone toxin and scorpion toxin to a common receptor site on the sodium channel. Binding of both 125I-labeled toxin derivatives is enhanced by the alkaloids aconitine and batrachotoxin due to a decrease in KD for polypeptide toxin. Enhancement of polypeptide toxin binding by aconitine and batrachotoxin is precisely correlated with persistent activation of sodium channels by the alkaloid toxins consistent with the conclusion that there is allosteric coupling between receptor sites for alkaloid and polypeptide toxins on the sodium channel. The binding of both 125I-labeled scorpion toxin and 125I-labeled sea anemone toxin is reduced by depolarization due to a voltage-dependent increase in KD. Scorpion toxin binding is more voltage-sensitive than sea anemone toxin binding. Our results directly demonstrate voltage-dependent binding of both scorpion toxin and sea anemone toxin to a common receptor site on the sodium channel and introduce the 125I-labeled polypeptide toxin derivatives as specific binding probes of tetrodotoxin-insensitive sodium channels in cultured muscle cells.     

The detection of Fc-IgA receptors on T and non-T,non-B acute leukemic lymphoblasts

Fc-IgA receptors have been described on purified human T-lymphocyte populations from normal individuals. More recently, non-T-cell subpopulations bearing Fc-IgA receptors have also been described. In this study, receptors for the Fc portion of IgA were detected on both T and non-T, non-B leukemic lymphoblasts from 15 patients with acute lymphoblastic leukemia (ALL). From 1.6 to 6.8% of the T lymphoblasts of 7 patients expressed Fc-IgA receptors and 0.5 to 3.9% of the non-T, non-B lymphoblasts of the remaining 8 patients expressed Fc-IgA receptors. The expression of IgA receptors on these cells may reflect the maturational state of these leukemic lymphoblasts. The detection of Fc-IgA receptors on leukemic lymphoblasts suggests that expression of these receptors on lymphoid cells represents an early maturational event.