Natural antisense transcripts with coding capacity in Arabidopsis may have a regulatory role that is not linked to double-stranded RNA degradation.
BACKGROUND
Overlapping transcripts in antisense orientation have the potential to form double-stranded RNA (dsRNA), a substrate for a number of different RNA-modification pathways. One prominent route for dsRNA is its breakdown by Dicer enzyme complexes into small RNAs, a pathway that is widely exploited by RNA interference technology to inactivate defined genes in transgenic lines. The significance of this pathway for endogenous gene regulation remains unclear.


RESULTS
We have examined transcription data for overlapping gene pairs in Arabidopsis thaliana. On the basis of an analysis of transcripts with coding regions, we find the majority of overlapping gene pairs to be convergently overlapping pairs (COPs), with the potential for dsRNA formation. In all tissues, COP transcripts are present at a higher frequency compared to the overall gene pool. The probability that both the sense and antisense copy of a COP are co-transcribed matches the theoretical value for coexpression under the assumption that the expression of one partner does not affect the expression of the other. Among COPs, we observe an over-representation of spliced (intron-containing) genes (90%) and of genes with alternatively spliced transcripts. For loci where antisense transcripts overlap with sense transcript introns, we also find a significant bias in favor of alternative splicing and variation of polyadenylation.


CONCLUSIONS
The results argue against a predominant RNA degradation effect induced by dsRNA formation. Instead, our data support alternative roles for dsRNAs. They suggest that at least for a subgroup of COPs, antisense expression may induce alternative splicing or polyadenylation.
Jen
Chih-Hung
CH
School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, UK. bmbcj@leeds.ac.uk
Michalopoulos
Ioannis
I
Westhead
David R
DR
Meyer
Peter
P
D017398:Alternative Splicing / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics*; D005091:Exons / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics; D007438:Introns / Q000235:genetics; D046228:Microarray Analysis; D016366:Open Reading Frames / Q000235:genetics*; D026723:Polyadenylation / Q000235:genetics; D020871:RNA Stability / Q000235:genetics*; D016372:RNA, Antisense / Q000235:genetics*; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid
D016372:RNA, Antisense; D012330:RNA, Double-Stranded