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T S Ro-Choi

Publications and source records attributed to T S Ro-Choi.

At least 19 recordsLinked to original sources
PubMed1999

Nuclear snRNA and nuclear function (discovery of 5' cap structures in RNA).

In view of the fact that eukaryotic gene expression starts in the nucleus, it is important to have a thorough understanding of nuclear macromolecular structure and function. Newly discovered snRNAs are eukaryotic cell specific and have unique subnuclear compartmental localizations. There are over 200 nucleolar-specific RNAs that include some abundant U3, U8, and U13 RNAs. Extranucleolar-nuclear-specific RNAs (snRNA) are 4.5S RNA I, II, III, 5S RNA III, U1, U2, U4, U5, and U6, in addition to over 500 different RNA species reported up to now. In particular, some snoRNAs and snRNAs have trimethylguanosine cap structures that are not present in bacteria. They have crucial roles in gene expression, such as transcription (U3 snoRNA), processing (U3, U8, U13, U14, U22, and 7-2/MRP), methylation (U14-16, U18, U20-21, and U24-63), pseudouridylation (E2, E3, U19, U23, and U64-72), and hnRNA splicing (U1, U2, U4, U5, and U6 snRNA).

Base Sequence↗
PubMed1976

Effects of alpha-amanitin, cycloheximide, and thioacetamide on low molecular weight nuclear RNA.

Studies were made on the effects of alpha-amanitin, cycloheximide, and thioacetamide on synthesis and content of low molecular weight nuclear RNA. Cycloheximide, an inhibitor of protein synthesis and the synthesis of 45S pre-rRNA and 5S RNA, also inhibited synthesis of nuclear U1 and U3 RNAs. alpha-Amanitin, an inhibited the synthesis of U1 and U2 low molecular weight nuclear RNA. Thioacetamide, which induces nucleolar hypertrophy and increased nucleolar RNA polymerase activity, markedly increased synthesis of 5.8S RNA and U3 RNA. These results show that syntheses of individual low molecular weight nuclear (LMWN) RNAs are controlled by different regulatory mechanisms. In particular, there appears to be a specific relationship between U3 RNA and functional states of the nucleolus.

Acetamides↗
PubMed1975

Nuclear ribonucleoprotein complexes containing U1 and U2 RNA.

Nuclear ribonucleoprotein (RNP) complexes that contain the U1 and U2 RNA of chromatin of Novikoff hepatoma cells were extracted with 0.01 M Tris-HCl (pH 8.0) after the nuclei were initially washed with 0.075 M NaCl and 0.025 M EDTA (pH 8.0). These RNP complexes were purified by chromatography on Sepharose 6B columns and centrifugation on sucrose density gradients. The identity of the U1 and U2 RNA in these particles was established by their electrophoretic mobility in polyacrylamide gels and their T1 RNase fingerprints which were identical with those of authentic U1 and U2 RNA (R. Reddy et al. (1974), J. Biol. Chem.249, 6486-6494; H. Shibata et al. (1974), Mol. Cell. Biochem. 4, 3-19). The nuclear riboncleoproteins had a buoyant density of 1.47 g/ml in CsCl gradients. Two-dimensional polyacrylamide gel electrophoresis of their proteins showed these RNP complexes contain 10 polypeptide spots, of which two are phosphorylated in vivo.

Animals↗
PubMed1975

The primary nucleotide sequence of nuclear U-2 ribonucleic acid. The 5'-terminal portion of the molecule.

The nuclear U-2 RNA which is highly modified (Reddy, R., Ro Choi, T.S., Henning, D., Shibata, H., Choi, Y.C., and Busch H. (1972) J. Biol. Chem. 247, 7245-7250) contains 13 pseudouridylic acid residues, 10 2'-O-methylated nucleotides and two modified bases including N-2,2, 7-trimethyl guanylic acid in its 5'-terminal portion (69 nucleotides). With the determination of this sequence and its overlap with the 3' portion of the molecule (nucleotides 70 to 196), the over-all nucleotide sequence of this RNA is:(see article). The concentration of modified nucleotides in its 5' portion is greater than for any RNA sequenced thus far.

Base Sequence↗
PubMed1975

Nucleotide sequence of U-2 ribonucleic acid. The sequence of the 5'-terminal oligonucleotide.

The nucleotide sequences were determined for the 5'-oligonucleotides obtained by complete pancreatic RNase digestion (P25) and complete T1 RNase digestion (T27) of U-2 RNA. Complete digestion of oligonucleotide P25 with snake venom phosphodiesterase produced pm3 2,2,7G, pAm, pUm, and pCp in approximately equimolar ratios. Partial digestion of these oligonucleotides with snake venom phosphodiesterase produced -Um-C-Gp and pAm-Um, indicating the sequence of the 3'-terminal portion of the 5'-oligonucleotide is pAm-Um-C-Gp. The 5'-terminal oligonucleotide did not contain a 5'-phosphate and no free nucleoside was released from the 5' end by venom phosphodiesterase digestion. Since free pm3 2,2,7G was released by digestion with nucleotide pyrophosphatase and limited digestion with snake venom phosphodiesterase, this nucleotide is apparently linked to pAm in a pyrophosphate linkage. Mass spectrometry and thin layer chromatography in borate systems showed the ribose of m3 2, 2, 7G contains no 2'O-methyl residue. Moreover, the finding that the ribose of m3 2, 2, 7G was oxidized by NaIO4 and reduced by KB3H4 in intact U-2 RNA rules out other linkages involving the 2' and 3' positions. Accordingly, it is concluded that the structure of the 5'-terminal pentanucleotide of U-2 RNA is(see article).

Alkaline Phosphatase↗