ORGANIC
LETTERS
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Vol. XX, No. XX
000–000
Chemical Synthesis of U1 snRNA
Derivatives
Akihiro Ohkubo,*,† Yasushi Kondo,‡ Makoto Suzuki,† Haruki Kobayashi,†
Takashi Kanamori,† Yoshiaki Masaki,† Kohji Seio,† Kiyoshi Nagai,‡ and MitsuoSekine*,†
Department of Life Science, Tokyo Institute of Technology, 4259 Nagatsuta, Midoriku,
Yokohama 226-8501, Japan, and MRC Laboratory of Molecular Biology, Francis Crick
Avenue, Cambridge Biomedical Campus, Cambridge, CB2 0QH, U.K.
aohkubo@bio.titech.ac.jp; msekine@bio.titech.ac.jp
Received July 8, 2013
ABSTRACT
U1 snRNA is an interesting biological tool for splicing correction and regulation of gene expression. However, U1 snRNA has never been chemically
synthesized. In this study, the first chemical synthesis of U1snRNA and its analogues was carried out. Moreover, it was found that the binding affinity
of the modified U1 snRNA with an ethylene glycol linkage to snurportin 1 (nuclear import adaptor) was as high as that of the unmodified RNA.
Uridine-rich small nuclear RNAs (U snRNAs) are
involved in very important pre-mRNA splicing events in
the nucleus of eukaryotic cells.1 Among them, U1snRNA can
recognize the 50-splice site of pre-mRNA. At the first splicing
step, U1snRNA directly binds to the splice site by hybridiza-
tion between the 50-terminal eight nucleotides of U1snRNA
and the complementary sequence of pre-mRNA.2
Splicing disorders are estimated to account for about
15% of disease-causing mutations in humans, and the
majority of genetic mutations are point mutations within
the sequences of splice sites.3 A subset of these defects
should result from mismatched base pairs between
U1snRNA and mutant pre-mRNAs. It was reported in a
recent study that mutant pre-mRNA splicing could be
promoted by modified U1snRNAs that were prepared
using the biological technique in the cell and could hybri-
dize with the mutant pre-mRNA.4 These results indicate
that modified U1snRNA could be useful for splicing
correction in gene therapy.
Additionally, a modified U1snRNA containing the
sequence complementary to the 30-terminal exon of the
targeted gene can downregulate the targeted gene expres-
sion via U1 interference (U1i).5 This downregulation
results from inhibition of mRNA polyadenylation by the
U1 snRNA-binding protein (U1ꢀ70K protein). However,
U1 snRNA has never been chemically synthesized because
U1 snRNA is very long (164 nt) and contains a compli-
cated 50-terminal 2,2,7-N-trimethylguanosine (m32,2,7G)
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† Tokyo Institute of Technology.
‡ MRC Laboratory of Molecular Biology.
€
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r
10.1021/ol401917r
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