Biology Reference
In-Depth Information
Alu sequence
DM
5
Exon
3
dsRBD1
dsRBD2
Alu sequence
Figure 3.3. Transcripts encoding Alu repeat elements are often present in introns of transcripts. If
two are present in opposite orientation less than 2 kb apart they can base pair with the
other and form a duplex structure that is edited by ADARs.
may act to inhibit retrotransposition; however, there is no real evidence to either
support or contradict this hypothesis and editing of
Alu-
containing transcripts
may have a novel biological role.
Recently, massively parallel amplification and deep-sequencing were
performed to find potential human editing sites in nonrepetitive sequences at
computationally predicted editing sites. Amplification of these small regions
using unique linked primers that form a “padlock” across potential editing sites
and high-throughput sequencing (Li
, 2009) identified 10 known edited
transcripts, along with 207 new transcripts that were edited in two tissues greater
than 5%. The number of new edited transcripts increased dramatically when the
stringent selection criteria were relaxed as many transcripts showed low levels of
editing (
et al.
5%) and were only edited in one tissue. Of the sites identified, 55
occurred in coding regions and 38 led to amino acid changes. Editing of tran-
scripts also varied between tissues and within brain regions. Next generation
sequencing technology has made the identification and verification of novel
editing sites easier; however, the functional consequences of these newly identi-
fied editing events have yet to be elucidated.
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IX. CONSEQUENCES OF INOSINE IN TRANSCRIPTS
Deamination of adenosine bases in RNA results in transcripts that contain one or
many inosine bases, which can have different consequences for the cell. If editing
occurred within coding sequences, the inosine base is read as guanosine by the
translation machinery which can lead to a recoding event so that a different
amino acid is inserted that can change the properties of proteins as is the case with
