Pseudouridylate

Posttranslational modification of preformed polynucleotides can generate additional bases such as pseudouridine, in which D-ribose is linked to C-5 of uracil by a carbon-to-carbon bond rather than by a P-N-glycosidic bond. The nucleotide pseudouridylic acid T arises by rearrangement of UMP of a preformed tRNA. Similarly, methylation by S-adenosylmethionine of a UMP of preformed tRNA forms TMP (thymidine monophosphate), which contains ribose rather than de-oxyribose. 

The substituents at the 5 or 6 position of the pyrimidine base have no relation to the susceptibility to RNase T2. Madison and Holley 93) have shown that RNase T2 is able to split the phosphodiester bonds of pseudouridylic acid and 5,6-dihydrouridylic acid. Recently, Saneyoshi et al. 86) have found a new minor constituent, Vp, with 5-methyl cytidine 3 -phosphate and other mononucleotides on the two-dimensional paper chromatogram of RNase T2 exhaustive digest of E. coli tRNAVal later the structure of V was proved to be uridine-5-oxyacetic acid 94). 

Darzacq X, Jady BE, Verheggen C, Kiss AM, Bertrand E, Kiss T. Cajal body-specific small nuclear RNAs a novel class of 2 -0-methylation and pseudouridylation guide RNAs. EMBO J. 2002 21(11) 2746-2756. 

The types of nucleoside or nucleotide modifications range from alterations of the base component to changes in the sugar or phosphate moieties. The natural modifications include pseudouridylation (generation of a C-glycoside), methylation. 

Many unusual nucleotides have been found as minor components of nucleic acids, especially in the soluble or transfer ribonucleic acids. Most of these minor components contain methylated aglycons in their structure. A review of these nucleotides has been presented by Dekker, and general techniques for their isolation as nucleosides have been reported by Hall. In addition, 5,6-dihydrouridylic acid (34) has been isolated by enzymic hydrolysis of certain transfer ribonucleic acids from yeast, and 4-thiouridylic acid (35) was obtained from the alkaline hydrolyzate of transfer ribonucleic acid from Escherichia coli. A nucleotide whose ultraviolet absorption spectrum was very similar to that of 2-thiouridine has been reported to be present in transfer ribonucleic acid. Although the a anomer (36) of cytidylic acid has been detected (and identified) in a yeast ribonucleic acid hydrolyzate, it is not certain whether this -cytidylic acid is a minor component of ribonucleic acid or an artifact produced during the alkaline hydrolysis. Among the minor nucleotide components of transfer ribonucleic acid, pseudouridylic acid (37)89-98 jg unique, in that the D-ribosyl moiety is linked to the aglycon... 

Matsushita, T. and F.F. Davis Studies of pseudouridylic acid synthetase from various sources Biochim. Biophys. Acta 238 (1971) 165-173. 

F ure 28 The Process of Pseudouridylation. [2344] Reference Appendix 2, Explanations to the Figures... 

Figure 28. Pseudouridylation [2344] H/ACA-hox signature hairpin adenine cytosine adenine. Functional in archaea. Appear in first stem loop in Ciona intestinalis. Described in Giardia and Trichomonas. Human box H/ACA analyzed (Chen XS Penny D Collins U BMC Genomics 2011 12 550. Kiss AM J y B Bertrand E Kiss T Mol CeU Biol 2004 21 5797-5807).

Figure 29-3. Structure of tRNA. Left sequence and projection of the conformation. The numbering corresponds to the phenyl alanine specific tRN A of yeast. A, Adenyl nucleoside C, cytosyl nucleoside G, guanidyl nucleoside T, thymidyl nucleoside U, uridyl nucleoside. In the case of the pseudouridyl residue the base is joined to the sugar via the C Pu is a purine nucleotide, Py is a pyrimidine nucleotide, and H is what is known as a hypermodified purine nucleotide. The other positions can be taken by any desired nucleotide, but must be complementary in the case of the hydrogen bonds signified by —. w, Wobble base. Right Spatial structure.

Ofengand, J., Henes, C. The function of pseudouridylic acid in transfer ribonucleic acid II. Inhibition of amino acyl transfer ribonucleic acid-ribosome complex formation by ribothymidylylpseudouridylyl-cytidylyl-guanosine 3 -phosphate, J. biol. Chem. 244, 6241-6253 (1969)... 

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