Modified nucleotides in T1 RNase oligonucleotides of 18S ribosomal RNA of the Novikoff hepatoma

Abstract

The primary structure of 18S rRNA of the Novikoff hepatoma cells was investigated. Regardless of whether the primary sequence of 18S rRNA is finally determined by RNA sequencing methods or DNA sequencing methods, it is important to identify numbers and types of the modified nucleotides and accordingly the present study was designed to localize the modified regions in T1 RNase derived oligonucleotide. Modified nucleotides found in 66 different oligonucleotide sequences included 2 m62A, 1 m6A, 1 m7G, 1m1cap3psi, 7 Cm, 13 Am, 9 Gm, 11 Um, and 38 psi residues. A number of these modified nucleotides are now placed in defined sequences of T1 RNase oligonucleotides which are now being searched for in larger fragments derived from partial T1 RNase digests of 18S rRNA. Improved homochromatography fingerprinting (Choi et al. (1976) Cancer Res. 36, 4301) of T1 RNase derived oligonucleotides provided a distinctive pattern for 18S rRNA of Novikoff hepatoma ascites cells. The 116 spots obtained by homochromatography contain 176 oligonucleotide sequences.

WBSCR22/Merm1 is required for late nuclear pre-ribosomal RNA processing and mediates N7-methylation of G1639 in human 18S rRNA

“…Bud23 mediates the N 7 -methylation of G1575 in the yeast 18S rRNA (White et al 2008) and this modification is also conserved in human 18S rRNA (m 7 G1639) ( Fig. 3A; Choi and Busch 1978;Piekna-Przybylska et al 2008). We therefore analyzed whether WBSCR22 is required for this modification, which is the only known m 7 G residue in human 18S rRNA (Choi and Busch 1978;Piekna-Przybylska et al 2008).…”

“…3A; Choi and Busch 1978;Piekna-Przybylska et al 2008). We therefore analyzed whether WBSCR22 is required for this modification, which is the only known m 7 G residue in human 18S rRNA (Choi and Busch 1978;Piekna-Przybylska et al 2008). To detect the methylation status of the rRNA in the presence and after depletion of WBSCR22, we took advantage of the specific reactivity of the m 7 G modification to aniline.…”

Pseudouridylation of yeast ribosomal precursor RNA

“…cations e.g. -Um-Gm-4-and -Um-A-*-in yeast 26-S rRNA, -*m-, -Am-C-* and -Um-Gm-*-in HeLa cell 28-S rRNA (8) and -Um-U-*-,-*-Gm-and -*-U-Gm-in 18-S rRNA of,Novikoff hepatoma cells (28). How are all these sites recognized by the modifying enzymes?…”

Sequence of the 3′‐terminal domain of mouse 18 S rRNA

“…They also found an extra G (position 7) that we have not detected; this nucleotide was not detected any more when mouse 18 S rRNA was reverse-transcribed [26] and does not exist in another independently cloned mouse rDNA fragment [28], as indicated by the presence of the Sau3A restriction site (recognition sequence GATC) in identical location as compared with our pMEB3 cloned fragment. This G is not present either in the rat 18 S rRNA as demonstrated by sequencing of a 32 nucleotide-long rRNA fragment (segment 5-36) after in vitro terminal labelling [29] or by homochromatography fingerprinting of total T 1 RNase oligonucleotides of 18 S rRNA [30]. [30].…”

“…This G is not present either in the rat 18 S rRNA as demonstrated by sequencing of a 32 nucleotide-long rRNA fragment (segment 5-36) after in vitro terminal labelling [29] or by homochromatography fingerprinting of total T 1 RNase oligonucleotides of 18 S rRNA [30]. [30]. The phylogenetic conservation seems to rule out that these sequence discrepancies rely upon our sequencing of a non-functional ribosomal gene (such a gene would be expected to have diverged more extensively than a functional one, due to the lack of selective pressure).…”