Tiny player join transcription initiation

  In a decade, small non-protein coding RNAs - snoRNAs, miRNAs, siRNAs, piRNAs - have been spotlighted as regulators of gene expression at many pathway and tissues. Each class of small RNAs is classified by specific size, biogenesis, and mechanism, and plays a pivotal role in a wide range of biochemical processes beyond the strong bias that introns are just evolutionary debris. Recently, Taft group suggested a novel class of small RNA which may be common characteristics of the transcription initiation, and therefore named as ‘Transcription initiation RNAs (tiRNAs)’

  In the analysis of human, chicken and drosophila RNA sequences, the length of tiRNAs ranged 12-29 nucleotides, which is relatively shorter than any other classes of small RNAs, and in the collaboration with FANTOM 4 project the modal size of them was identified as 18 nucleotides. Remarkably, tiRNAs map to translation start sites (-60 to +120 nucleotides) and are originated from the same strand with TSSs. Moreover, the association with high G+C promoters and major distribution at downstream of TSSs were also found. Inferring from above evidences, Taft groups proposed that tiRNAs may be the result of RNAPII backtracking and stalling.

Joon Yong An

(42057505)

For more read, http://www.nature.com/ng/journal/v41/n5/full/ng.312.html