On July 11, 2016, Chirlmin Joo, associate professor of Delft University, visited Institute of Biophysics, Chinese Academy of Sciences and gave a lecture entitled “Why Argonaute is needed to make microRNA target search fast and reliable ” in the library. Professor WANG Yanli hosted this lecture, and many researchers and graduate students listened the interesting report. 

Associate professor Chirlmin Joo got his PhD degree from University of Illinois at Urbana-Champaign and then pursued a postdoctoral training in Seoul National University. Now he is the associate professor and principle investigator in the Department of BioNanoScience, Delft University of Technology. His research focuses on single-molecule, such as microRNA, CRISPR, protein sequencing. 

During his lecture, Doctor Chirlmin Joo gave a brief introduction of Fluorescence Resonance Energy Transfer (FRET). MicroRNA (miRNA) interferes with the translation of cognate messenger RNA (mRNA) by finding, preferentially binding, and marking it for degradation. To facilitate the search process, Argonaute (Ago) proteins come together with miRNA, forming a dynamic search complex. By using single-molecule FRET to directly visualize how human Argonaute-2 (Ago2) searches for and identifies target sites in RNAs complementary to its miRNA guide, and thier results suggest that Ago2 initially scans for target sites with complementarity to nucleotides 2–4 of the miRNA. Associate professor Chirlmin Joo discussed how Argonaute used these mechanisms to overcome so-called the speed-stability paradox in target search and efficiently identify miRNA target sites within the vast and dynamic agglomeration of RNA molecules in the cell. Recent observations with bacterial Ago proteins were also presented. 

This lecture was inspiring and very impressive for all the audience. After the lecture, associate professor Chirlmin Joo and the audience shared their views and interests on the issues of both concern.