Portal de Periódicos da CAPES

Characterization and subcellular localization of 7-8 S RNAs of Novikoff hepatoma.

1981; Elsevier BV; Volume: 256; Issue: 16 Linguagem: Inglês

10.1016/s0021-9258(19)68864-2

1083-351X

R Reddy, W.Y. Li, D Henning, Yuri Choi, Katsuhiko Nohga, H. Busch,

RNA Research and Splicing

Five distinct 7-8 S small nuclear RNAs from Novikoff hepatoma were characterized by fingerprinting and their subcellular localization.Two of these RNAs (7-1 and 7-2) were not found earlier.A 7 S RNA previously reported to be localized to cytoplasm was found in nuclei in amounts of 30-50% of the total.RNA 7-3 was nucleoplasmic and was -different from 7 S RNA.Several RNAs, 7-1, 7-2, 8 A, and 8 B, were found in nucleoli.The RNAs 7-1 , 8 A, and 8 B were released from nucleolar 28 S RNA extracted at 25 "C by heating the RNA to 65 "C.The TI RNase fingerprints of RNAs 8 A and 8 B were very similar.The similarities of the fingerprints of the 7 S RNAs of HeLa and Novikoff hepatoma cells support earlier suggestions that these RNAs are conserved through evolution.Several small RNAs (90-400 nucleotides long) which are not directly involved in protein synthesis have been well characterized (1-17).Based on their nuclear localization, these small RNAs were classified as small nuclear RNAs, small cytoplasmic RNAs, and small nucleolar RNAs.The abundant snRNAs' were named U1, U2, and U3 RNAs, since these were found to be uridylic acid-rich compared to ribosomal RNAs (1).Many of the small RNAs are well characterized and the sequences of all known capped snRNAs, U1 (8-lo), U2 (7, l l ) , U3 (12,13), U4 (14), U5 (7,15), and U6 ( 16) have been defined.Recently, sera from some patients with systemic lupus erythematosus were shown to precipitate small ribonucleoproteins.Four such antibodies (anti-ribonucleoprotein, anti-Sm, anti-La, and anti-Ro) were shown to precipitate distinct sets of ribonucleoproteins (17-19).Recent reports have implicated the uridine-rich snRNAs in processing of heterogeneous nuclear RNAs (20,21) and results supporting this hypothesis have been reported (22,23).In view of the potentially important cellular functions of these small RNAs, the 7-8 S RNAs were analyzed.Of the five distinct RNAs studied, only 7 S RNA had been characterized previously (24,25).The present study shows there are three new distinct nucleolar RNAs which differ from the 8 S and 7-3 RNAs previously analyzed (26, 27). MATERIALS AND METHODSNovikoff hepatoma cells were incubated with ["'Plphosphate for