ERRATUM
Volume 87, no. 8, p. 4272–4280, 2013. Page 4272: The byline should appear as shown above.
Page 4272, column 2, shaded box: The present address footnote should read “* Present address: Zhijing Huang, Department of Biology, Indiana University, Bloomington, Indiana, USA; Vasanthi Avadhanula, Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.”