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H Busch

Publications and source records attributed to H Busch.

At least 199 records · Page 11Linked to original sources
PubMed1981

Ubiquitin - protein conjugates.

The data available at present indicates there are three distinct functions of ubiquitin, two of which are related to protein conjugation. The first of these has been extensively studied by our laboratory and others interested in nucleosomes and changes in chromatin states. The ubiquitin-histone (Ub-2A, Ub-2B) conjugation reaction now appears to be a very dynamic process. In the deconjugation (lyase) reaction, both the histone 2A and the ubiquitin are left intact and in a form which makes possible ready reconjugation. Accordingly, this may be a mechanism for "moment-to-moment" Control of the genome. The second function in which ubiquitin is conjugated involves proteolytic activity. This activity is correlated with protein turnover. In this process, the ubiquitin-protein conjugate apparently serves as a "signal" for the protease cleavage of the protein. The released ubiquitin is also intact and is probably available for reconjugation. In the third function, ubiquitin was suggested to serve as a "hormone". The studies thus far have been carried out primarily on induction of T- and B-lymphocytes, reduction or delay of Coombs' positivity and reduction of spleen weight. The precise physiological role of this reported function is still unclear, particularly because the ubiquitin used was probably not the physiologically active form.

Amino Acid Sequence↗
PubMed1981

Primary and secondary structure of U2 snRNA.

With the improved rapid sequencing techniques, the earlier sequence of U2 RNA of Novikoff hepatoma (Shibata et al, J. Biol. Chem. 250, 3909-3920, 1975) was reanalyzed and modified. The improved sequence of U2 RNA is 188 (or 189) nucleotides long and is in register with a characterized U2 RNA pseudogene (Denison et al, PNAS 78, 810-814, 1981) except for an 11 nucleotide sequence (nucleotides 147-157) which is absent from the pseudogene. From these results, a secondary structure of U2 RNA is proposed which is supported by the preferred cleavage sites with T1-RNase, RNase A and S1 nuclease. Isolated U2 RNA was cleaved by T1-RNase preferentially at positions 64 and 164, whereas U2 RNA in U2-snRNP was cleaved only at position 64, indicating that position 164 is protected in U2-snRNP. As with U1 RNA (Epstein et al, PNAS 78, 1562-1566, 1981) the 5'-end of isolated U2 RNA was not preferentially cleaved by T1-RNase.

Animals↗
PubMed1981

The primary nucleotide sequence of U4 RNA.

U4 RNA is one of the "capped" nuclear snRNAs recently found to be precipitable by anti-Sm antibodies as ribonucleoprotein particles. U4 RNA, along with other snRNAs, has been implicated in hnRNA processing, mRNA transport, or both (Lerner, M. R., Boyle, J., Mount, S., Wolin, S., and Steitz, J. A. (1980) Nature 283, 220-224). Since the proteins bound to different snRNAs appear to be the same, the functions of different snRNPs might be dependent on the RNA components. To help understand the function of U4 RNP, the nucleotide sequence of U4 RNA was determined. The sequence is (formula see text) In addition to the modified nucleotides in the "cap," U4 RNA contains Am at position 63 and m6A at position 98. It also exhibited A-C microheterogeneity at position 97.

Animals↗
PubMed1981

Evidence for a species of nuclear actin distinct from cytoplasmic and muscles actins.

Nuclear actin (protein BJ) has been isolated from the chromatin of Novikoff hepatoma ascites cells and purified to homogeneity by selective extraction, Sepharose CL-6B chromatography, and preparative polyacrylamide gel electrophoresis. A comparison of nuclear and cytoplasmic actins from Novikoff hepatoma cells and rabbit muscle actin was made by amino acid analysis, isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and two-dimensional peptide mapping procedures. By these criteria, all of the proteins compared are actins, but each is chemically distinct. It was concluded, therefore, that nuclear actin is similar to, but not identical with, cytoplasmic actin isolated from Novikoff hepatoma cells. A striking similarity in peptide charge and migration as shown by peptide map analysis was observed for nuclear and rabbit skeletal muscle actins. This may indicate that nuclear actin has the capacity for contractile function. In addition, the actins synthesized in Novikoff hepatoma cells may results from more than two structural genes.

Actins↗
PubMed1981

Protein A24 lyase activity in nucleoli of thioacetamide-treated rat liver releases histone 2A and ubiquitin from conjugated protein A24.

Isolated liver nucleoli from rats treated for 3 days with thioacetamide contained an enzyme activity which specifically degraded conjugate protein A24. Two-dimensional polyacrylamide gel electrophoresis indicated that the amount of protein A24 in chromatin decreased during incubation at 37 degrees C for 60 min with these nucleoli. Concomitantly, a marked increase was found in the content of free ubiquitin, the nonhistone component of protein A24. Incubation of 3H-labeled protein A24 with the thioacetamide-treated liver nucleoli resulted in the linear release of 3H-labeled histone 2A and 3H-free ubiquitin in the presence of phenylmethanesulfonyl fluoride (PMSF) for 2 h. Pretreatment of the nucleoli with trypsin or by heating at 80 degrees C for 10 min inhibited their ability to cleave protein A24. Protein A24 lyase catalyzes the reaction: protein A24 leads to histone 2A plus ubiquitin.

Acetamides↗
PubMed1981

Cloning and characterization of a highly reiterated 5.8-kilobase pair nucleolar EcoRI DNA fragment found in Novikoff hepatoma ascites cells.

The DNA of Novikoff hepatoma ascites cells was found to contain a 3.6-megadalton EcoRI restriction fragment, referred to as EcoRI fragment A (Parker et al., 1979). C0t analyses demonstrated an enrichment of fragment A sequences in Novikoff hepatoma genome relative to normal rat liver DNA. This fragment was cloned in lambda gtWES to determine its molecular structure and sequence organization. The DNA from a positive clone was labeled by nick translation and hybridized to a Southern blot of EcoRI digested Novikoff DNA. Distinct hybrids formed with the region corresponding to fragment A. The greater degree of hybridization to the nucleolar fraction suggested a nucleolar enrichment of fragment A. Fragment A has a PstI site approximately 300 base pairs from one terminus which was used to generate mono-5'-32P-labeled fragments. The larger PStI subfragment, 5500 base pairs, labeled at a single terminus, was used to evolve a restriction enzyme map. The 300 base pair fragment was partially sequenced, revealing the presence of a repetitive sequence "island", TT(GTCT)8(GAAT)5G-. C0t analysis, utilizing the purified clone as a probe, confirmed the enrichment of fragment A sequences in the tumor relative to the normal rat liver control.

Animals↗
PubMed1981

Sequence of a phosphorylation site in nucleolar protein B23.

The sites of phosphorylation in protein B23, a silver-staining preribosomal ribonucleoprotein particle protein, were analyzed by tryptic peptide mapping. Three 32P peptides were found using in vitro labeling of nucleoli. An additional unlabeled phosphopeptide was identified by amino acid analysis. The sequence of the latter was Asp-Thr(P)-Pro-Ala-Lys. These results suggest that protein B23 contains one class of site labeled rapidly in vitro and another type of site phosphorylated only in vivo.

Adenosine Triphosphate↗
PubMed1981

Characterization of cloned rat ribosomal DNA fragments.

Two Charon 4A lambda bacteriophage clones were characterized which contain all and part o the 18S ribosomal DNA of the rat. One clone contained two Eco RI fragments which include the whole 18S ribosomal RNA region and part of 28S ribosomal RNA region. The other clone contained an Eco RI fragment which covers part of 18S ribosomal RNA region. There were differences between the two clones in the non-transcribed spacer regions suggesting that there is heterogeneity in the non-transcribed spacer regions of rat ribosomal genes. The restriction maps of the two clones were compared to the restriction map of the cloned mouse ribosomal DNA. Eco RI, Hind III, Pst I, and Bam HI sites in 18S ribosomal RNA regions were in the same places in mouse and rat DNA but the restriction sites in the 5'-spacer regions were different.

Animals↗
PubMed1981

Nucleolar immunofluorescence in bone marrow specimens of human hematological malignancies.

Leukemic cells and myeloma cells were studied in bone marrow of untreated patients with acute and chronic myeloid leukemia, chronic lymphocytic leukemia, and multiple myeloma to provide more information on the nucleolar immunofluorescence produced by antibodies no nucleoli of HeLa cells. The nucleolar immunofluorescence was mainly observed in myeloblasts of myeloid leukemias an in immature as well as mature cells of the plasmacytic or lymphocytic cell lines of multiple myeloma or chronic lymphocytic leukemia. With respect to the nucleolar immunofluorescence, both positive and negative populations of cells were noted in the specimens of all patients studied.

Antigens, Neoplasm↗