Talk abstracts

Talk on Saturday 11:00-11:20am submitted by Feng Xiao

Novel mechanism of hexamer assembly in protein/RNA interactions revealed by single molecule imaging.

Feng Xiao (Biomedical Engineering, University of Cincinnati), Hui Zhang (Biomedical Engineering, University of Cincinnati), Peixuan Guo (Biomedical Engineering, University of Cincinnati)

Abstract:
Many DNA or RNA-binding proteins form a hexameric ring, but the mechanism of hexamer assembly is poorly understood. The pRNA of bacteriophage phi29 DNA packaging motor also forms a hexameric ring. It is generally believed that the specificity in Protein/RNA interaction relies on molecular contact through a surface charge or 3D structure matching. Here we used single molecule studies to elucidate a mechanism suggesting that the specificity and affinity in Protein/RNA interaction relies on RNA static ring formation. A combined pRNA ring-forming group was very specific for motor binding, but the isolated individual members of the ring-forming group bind to the motor nonspecifically. pRNA did not form hexamer prior to motor binding. Only those RNAs that formed a static ring, via the interlocking loops, stayed on the motor. Single interlocking loop interruption resulted in pRNA falling off the motor. Extension or reduction of the ring circumference failed in motor-binding. This new mechanism was tested by redesigning two artificial RNAs that formed hexamer and drove the motor to package DNA and produce infectious virion phi29. Single molecule imaging confirmed that the copy number of pRNA on the motor is the common multiple of two and three, that is, a hexamer. This novel mechanism will be presented at this RNA meeting.

Keywords: phi29, pRNA, connector