Oeiras, 22.10.2015

Herpesviruses establish life-long latent infections. In this stage, a small subset of viral proteins ensures viral genome persistence in the host. Researchers from the Structural Virology Lab and collaborators have now gone one step further in understanding how the Kaposi's sarcoma-associated herpesvirus (KSHV) is able to persist inside the human host, by analysing the structure of one such protein – LANA – which promotes the DNA bending required for viral replication. The work is published in Nucleic Acids Research.

The Kaposi's sarcoma-associated herpesvirus is not pathogenic in healthy individuals but is highly oncogenic in HIV-1-infected and immuno-suppressed individuals. During latency, this herpesvirus (KSHV), persist as multicopy, circularized genomes in the cell nucleus and express a small subset of viral genes. LANA (KSHV latency-associated nuclear antigen) is the predominant gene expressed during latent infection. Researchers have previously shown how this protein is able to literally tie the viral DNA to the host chromosomes but how the binding of LANA promotes viral DNA replication initiation remained elusive.

Proteins such as LANA are thought to induce DNA bending, thereby facilitating DNA replication. In this work, researchers concluded that, in KSHV, LANA forms a bent oligomer assembly of two dimers: the binding of the first dimer promotes the cooperative binding of a second dimer and the formation of a tetramer induces DNA bending. Furthermore, the dimer-dimer assembly forms a hydrophobic pivot point, which gives both bend and rotational freedom for LANA to adopt variable conformations to accommodate multiple binding; this would allow greater freedom in its assembly and contribute to the persistence of the virus in the human host. Surprisingly, a homolog protein from a mouse virus (MHV-68) adopts a rigid linear conformation instead, suggesting that the viruses have evolved different strategies to promote DNA tethering and replication.

This work results from a collaboration between researchers at ITQB, IMM, European Molecular Biology Laboratory (Germany), and Harvard Medical School (USA).

LANA 3D structure exhibiting the rotation that allows variable conformations to accommodate multiple binding and thus contributes to the persistence of the virus in the human host

Original Article

Nucl. Acids Res. (2015) doi: 10.1093/nar/gkv987 (Open Access)

KSHV but not MHV-68 LANA induces a strong bend upon binding to terminal repeat viral DNA

Rajesh Ponnusamy¹, Maxim V. Petoukhov², Bruno Correia¹, Tania F. Custodio¹, Franceline Juillard³, Min Tan³, Marta Pires de Miranda⁴, Maria A. Carrondo¹, J. Pedro Simas⁴, Kenneth M. Kaye³, Dmitri I. Svergun² and Colin E. McVey¹

1 ITQB
2 EMBL c/o DESY (Germany)
3 Brigham and Women's Hospital and Harvard Medical School (USA)
4 Instituto de Microbiologia e Instituto de Medicina Molecular (Portugal)