Crystal structure of the shutoff and exonuclease protein from the oncogenic Kaposi's sarcoma-associated herpesvirus.
The Kaposi's sarcoma-associated herpesvirus protein SOX (shut off and exonuclease) and its Epstein-Barr virus homolog, BGLF5, are active during the early lytic phase and belong to the alkaline nuclease family. Both proteins have been shown to be bifunctional, being responsible for DNA maturation as well as host shutoff at the mRNA level. We present the crystal structure of SOX determined at 1.85 A resolution. By modeling DNA binding, we have identified catalytic residues that explain the preferred 5'-exonuclease activity of the alkaline nucleases. The presence of a crevice suitable for binding duplex DNA supports a role for herpes alkaline nucleases in recombination events preceding packaging of viral DNA. Direct interaction with dsDNA is supported by oligonucleotide binding data. Mutations specifically affecting host shutoff map to a surface region of the N-terminal domain, implying an essential role in protein-protein interactions, and link the RNase activity of the enzyme to mRNA degradation pathways.
Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
Sue-Li
SL
Dahlroth
Daniel
D
Gurmu
Florian
F
Schmitzberger
Henrik
H
Engman
Juergen
J
Haas
Heidi
H
Erlandsen
Pär
P
Nordlund
D018360:Crystallography, X-Ray; D004247:DNA / Q000378:metabolism; D019288:Herpesvirus 8, Human / Q000201:enzymology* / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
D014764:Viral Proteins; D004247:DNA