1. MicroRNA regulation in Arabidopsis thaliana Diane Guo CUHK 6th IncoB, Aug.29, 2007

2. Outline • Background • Characterization of miRNA targets • Interactions between miRNAs and various cellular pathways • Coordinated regulation by miRNAs and transcription factors • Summary

3. microRNA • miRNAs are small endogenous RNA molecules (~22nt) found in plant and animals • Regulate gene expression through targeted mRNA cleavage or translational repression • Play critical roles in a variety of cellular processes such as development, cell proliferation, apoptosis, and stress response, etc

4. MiRNA processing and activity (borrowed from Ambion)

5. Mode of miRNA action in plants and animals (borrowed from Ambion)

6. Table 1 GO terms of miRNA targets (molecular function)

7. Table 2 Feature of miRNA target

8. Table 2 Feature of miRNA target

9. MiRNAs more frequently target genes with less transcription factor binding site

10. Summary • We systematically analyzed the characteristics of miRNA targets. MiRNAs with multi-gene families are more likely to target TFs, and miRNAs represented by single gene tend to target non-TFs. • To systematically investigate the interactions between miRNAs and various cellular pathways, we analyzed the miRNA targets distribution in the pathways and found that miRNAs regulate the pathway through selectively interacting with positive regulatory modules and highly connected nodes. • We found that miRNA preferentially target genes bearing less TFBSs. This suggests that the post-transcriptional regulation by miRNAs is coordinated with regulation at the transcriptional level by transcription factors.

11. Acknowledgement CUHK: Zhang Qing NEAU: Li Yong Zhu Yanming