Chemical incorporation of 1-methyladenosine, minor tRNA component, into oligonucleotides

Article abstract of DOI:10.1081/NCN-120022749

The synthesis of suitably protected 1-methyladenosine derivatives has been developed and its successful chemical incorporation into oligonucleotides was achieved.

Full text of DOI:10.1081/NCN-120022749

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Chemical Incorporation of 1-Methyladenosine, Minor
tRNA Component, into Oligonucleotides
E. V. Efimtseva a c , S. N. Mikhailov a , J. Rozenski b , R. Busson b , A. Van Aerschot b & P.
Herdewijn b
a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , Moscow, Russia
b Rega Institute Katholieke Universiteit Leuven , Leuven, Belgium
c Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , Vavilov str. 32,
119991, Moscow, Russia
Published online: 31 Aug 2006.
To cite this article: E. V. Efimtseva , S. N. Mikhailov , J. Rozenski , R. Busson , A. Van Aerschot & P. Herdewijn (2003)
Chemical Incorporation of 1-Methyladenosine, Minor tRNA Component, into Oligonucleotides, Nucleosides, Nucleotides and
Nucleic Acids, 22:5-8, 1113-1115, DOI: 10.1081/NCN-120022749
To link to this article: http://dx.doi.org/10.1081/NCN-120022749
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NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS
Vol. 22, Nos. 5–8, pp. 1113–1115, 2003
Chemical Incorporation of 1-Methyladenosine, Minor tRNA
Component, into Oligonucleotides
1
2
2
E. V. Efimtseva,1, S. N. Mikhailov, J. Rozenski, R. Busson,
*
A. Van Aerschot,2 and P. Herdewijn2
1Engelhardt Institute of Molecular Biology, Russian Academy of Sciences,
Moscow, Russia
2Rega Institute Katholieke Universiteit Leuven,
Leuven, Belgium
ABSTRACT
The synthesis of suitably protected 1-methyladenosine derivatives has been
developed and its successful chemical incorporation into oligonucleotides was
achieved.
Key Words: 1-Methyladenosine; Minor tRNA component; Chemical synthesis;
Oligonucleotides.
Modified nucleosides offer an overwhelming variety of chemistry and potential
biological functions. More than hundred modified nucleosides have been discovered
in nature, most of them occur in tRNAs. The contribution of these modifications to
the functional chemistry, structure and biological activity of the RNAs largely
*Correspondence: Ekaterina V. Efimtseva, Engelhardt Institute of Molecular Biology,
Russian Academy of Sciences, Vavilov str. 32, 119991 Moscow, Russia; Fax: þ7 095 135
1405; E-mail: smikh@imb.ac.ru.
1113
DOI: 10.1081/NCN-120022749
Copyright # 2003 by Marcel Dekker, Inc.
1525-7770 (Print); 1532-2335 (Online)
www.dekker.com

1114
Efimtseva et al.
remains to be discovered. Approximately 25% of all tRNAs have 1-methyladenosine
(m1A) at position 58 in the T loop.
Here we present our results on the preparation of m1A building block and its
successful incorporation into oligonucleotides (ONs). Previously oligoribonucleo-
tides containing m1A (1) were prepared using T4 RNA ligase[1]. To the best of our
knowledge before our recent publication[2] no attempts have been made for chemical
incorporation of m1A into ONs.
a. MMTrCl=Py; b. (ClCH2CO)2O=Py; c. tBuMe2SiCl; d. iPr2NPCl(OCH2CH2CN).
Under alkaline conditions, m1A (1) rearranges to N6-methyladenosine (m6A).[3]
m1A is difficult to handle due to its polar character. We have examined the stability
of 1 under different conditions of deblocking which are used in ON synthesis. In 25%
aq. ammonia the half-time of Dimroth rearrangement of 1 to m6A was 36 h at 20ꢀC.
However, 1 was stable at least for 3 days in 2 M NH3 in MeOH and for 2 days at
20ꢀC in 1M Bu4NF in THF.
Tritylation of the hydroiodide salt of 1[3] gave 2 in 68% yield. The benzoyl and
acetyl groups for base protection of 2 were found to be too stable towards NH3 in
MeOH.[2] Therefore, more labile chloroacetyl group was chosen. Compound 3 was
prepared in 80% yield using chloroacetic anhydride in pyridine with subsequent
cleavage of O-chloroacetyl groups with NH3 in MeOH (0ꢀC, 30 min). After silylation
20-isomer 4 was converted to the phosphoramidite 5 suitable for DNA and RNA
synthesis. Deblocking of base-labile groups should be done in anhydrous condi-
tions (2M NH3in MeOH 60 h, 20ꢀC). Mass spectrometry together with enzymatic
hydrolysis were used to prove ONs structure. The modification destabilizes a DNA
duplex but slightly improves the stability of a hairpin when incorporated into
the loop.
Authors thank KUL Research Council and RFBR for financial support.
REFERENCES
1. Helm, M.; Giege, R.; Florentz, C. A Watson-Crick base-pair-disrupting methyl
group (m1A9) is sufficient for cloverleaf folding of human mitochondrial
tRNALys. Biochemistry 1999, 38, 13,338–13,346.

1-Methyladenosine into Oligonucleotides
1115
2. Mikhailov, S.N.; Rozenski, J.; Efimtseva, E.V.; Busson, R.; Van Aerschot, A.;
Herdewijn, P. Chemical incorporation 1-methyladenosine into oligonucleotides.
Nucleic Acids Res. 2002, 30, 1124–1131.
3. Jones, J.W.; Robins, R.K. Purine nucleosides. III. Methylation studies of
certain naturally occurring purine nucleosides. J. Am. Chem. Soc. 1963, 85,
193–201.