Revealing Structure and Dynamics of Telomere Maintenance Proteins on DNA: One Molecule at a Time

Abstract

Telomeres play important roles in maintaining the stability of linear chromosomes. A specialized protein complex, called shelterin or telosome, binds to and protects telomeres at chromosome ends. Telomere maintenance involves dynamic actions of multiple proteins interacting with long repetitive sequences and complex dynamic DNA structures, such as T-loops. Furthermore, it was shown recently that in contrast to cohesion along chromosome arms, sister telomere association is a specialized process requiring a tighter association provided by the cohesin subunit SA1 in conjunction with specific proteins from the shelterin complex. To better understand the telomere maintenance pathways, we established complementary single-molecule imaging platforms: a newly developed Dual-Resonance-frequency-Enhanced Electrostatic force Microscopy (DREEM) technique capable of revealing DNA paths in protein-DNA complexes, fluorescence imaging of quantum dot-labeled proteins for tracking dynamics of proteins on DNA tightropes, and a nanochannel based imaging platform for studying protein-mediated DNA-DNA pairing/looping in real time. I will highlight our recent results on: 1) Revealing DNA paths inside TRF2 complexes during DNA compaction through DREEM. 2) Cohesin SA1 and shelterin protein TRF1 mediated sister telomere cohesion. 3) Dynamics of SA1 and TRF1 mediated DNA-DNA pairing inside nanochannels.