RT Journal Article
SR Electronic
T1 Super-Resolution Microscopy Reveals Structural Mechanisms Driving the Nanoarchitecture of a Viral Chromatin Tether
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 181016
DO 10.1101/181016
A1 Margaret J. Grant
A1 Matthew S. Loftus
A1 Aiola P. Stoja
A1 Dean H. Kedes
A1 Malcolm Mitchell Smith
YR 2017
UL http://biorxiv.org/content/early/2017/12/15/181016.abstract
AB By tethering their circular genomes (episomes) to host chromatin, DNA tumor viruses ensure retention and segregation of their genetic material during cell divisions. Despite functional genetic and crystallographic studies, there is little information addressing the three-dimensional structure of these tethers in cells, issues critical for understanding persistent infection by these viruses. Here, we have applied direct stochastic optical reconstruction microscopy (dSTORM) to establish the nanoarchitecture of tethers within cells latently infected with the oncogenic human pathogen, Kaposi's sarcoma-associated herpesvirus (KSHV). Each KSHV tether comprises a series of homodimers of the latency-associated nuclear antigen (LANA) that bind with their C-termini to the tandem array of episomal terminal repeats (TRs) and with their N-termini to host chromatin. Super-resolution imaging revealed that individual KSHV tethers possess similar overall dimensions and, in aggregate, fold to occupy the volume of a prolate ellipsoid. Using plasmids with increasing numbers of TRs, we found that tethers display polymer power-law scaling behavior with a scaling exponent characteristic of active chromatin. For plasmids containing a two-TR tether, we determined the size, separation, and relative orientation of two distinct clusters of bound LANA, each corresponding to a single TR. From these data, we have generated a three-dimensional model of the episomal half of the tether that integrates and extends previously established findings from epi-fluorescent, crystallographic, and epigenetic approaches. Our findings also validate the use of dSTORM in establishing novel structural insights into the physical basis of molecular connections linking host and pathogen genomes.