PMID: 26370092

Authors:

Musayev FN, Zarate-Perez F, Bishop C, Burgner JW 2nd, Escalante CR

Title:

Structural Insights into the Assembly of the Adeno-Associated Virus Type 2 Rep68 Protein on the Integration site AAVS1.

Journal:

J Biol Chem. 2015 Sep 14. pii: jbc.M115.669960.

Abstract:

Adeno-Associated virus (AAV) is the only eukaryotic virus with the property of establishing latency by integrating site-specifically into the human genome. The integration site known as AAVS1 is located in chromosome 19 and contains multiple GCTC repeats that are recognized by the AAV non-structural Rep proteins. These proteins are multifunctional, with an N-terminal origin-binding domain (OBD) and a helicase domain joined together by a short linker. As a first step to understand the process of site-specific integration, we set up to characterize the recognition and assembly of Rep68 onto the AAVS1 site. We first determined the X-ray structure of AAV-2 Rep68 OBD in complex with the AAVS1 DNA site. Specificity is achieved through the interaction of a glycine-rich loop that binds the major groove and an alpha-helix that interacts with a downstream minor groove on the same face of the DNA. Although the structure shows a complex with three OBD molecules bound to the AAVS1 site, we show using analytical centrifugation and electron microscopy that the full length Rep68 forms a heptameric complex. Moreover, we determine that a minimum of two direct repeats is required to form a stable complex and melt DNA. Finally, we show that although the individual domains bind DNA poorly, complex assembly requires oligomerization and cooperative between its OBD, helicase and the linker domains.