ANRIL/CDKN2B-AS shows two-stage clade-specific evolution and becomes conserved after transposon insertions in simians.
BACKGROUND
Many long non-coding RNA (lncRNA) genes identified in mammals have multiple exons and functional domains, allowing them to bind to polycomb proteins, DNA methyltransferases, and specific DNA sequences to regulate genome methylation. Little is known about the origin and evolution of lncRNAs. ANRIL/CDKN2B-AS consists of 19 exons on human chromosome 9p21 and regulates the expression of three cyclin-dependent kinase inhibitors (CDKN2A/ARF/CDKN2B).


RESULTS
ANRIL/CDKN2B-AS originated in placental mammals, obtained additional exons during mammalian evolution but gradually lost them during rodent evolution, and reached 19 exons only in simians. ANRIL lacks splicing signals in mammals. In simians, multiple transposons were inserted and transformed into exons of the ANRIL gene, after which ANRIL became highly conserved. A further survey reveals that multiple transposons exist in many lncRNAs.


CONCLUSIONS
ANRIL shows a two-stage, clade-specific evolutionary process and is fully developed only in simians. The domestication of multiple transposons indicates an impressive pattern of "evolutionary tinkering" and is likely to be important for ANRIL's structure and function. The evolution of lncRNAs and that of transposons may be highly co-opted in primates. Many lncRNAs may be functional only in simians.
Sha
S
He
Weiling
W
Gu
Yize
Y
Li
Bioinformatics Section, School of Basic Medical Sciences, Southern Medical University, Shatai Road, Guangzhou 510515, China. hao.zhu@ymail.com.
Hao
H
Zhu
D000818:Animals; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D004251:DNA Transposable Elements; D019143:Evolution, Molecular; D005091:Exons; D015186:Hominidae / Q000235:genetics; D006801:Humans; D008322:Mammals / Q000235:genetics*; D012326:RNA Splicing; D062085:RNA, Long Noncoding / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid
C561518:CDKN2B antisense RNA, human; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D004251:DNA Transposable Elements; D062085:RNA, Long Noncoding