ACTIVITIES OF ADENOVIRUS VIRUS-ASSOCIATED RNAS - PURIFICATION AND CHARACTERIZATION OF RNA-BINDING PROTEINS

Most human adenoviruses encode two virus-associated (VA) RNAs, VA RNA( I) and VA RNA(II), that accumulate to high levels in the cytoplasm of infected cells. The function of VA RNA(I) in blocking the activation o f the cellular kinase PKR is well known, but the role of VA RNA(II) is obscure. Herein we characterize and purify several human proteins tha t interact preferentially with VA RNA(II) in Northwestern blot assays. Two of these proteins were identified as RNA helicase A and NF90, a c omponent of the heterodimeric nuclear factor of activated T cells (NFA T), They copurified with the smaller NFAT subunit, NF45, which did not bind VA RNA(II), and with an unidentified protein, p97, which did bin d VA RNA(II). Both RNA helicase A and NF90 contain two copies of a dou ble-stranded (ds) RNA binding motif and bind strongly to dsRNA. NF90 i nteracts with RNAs in the following order of affinity: dsRNA > VA RNA( II) > VA RNA(I) > single-stranded RNA. Furthermore, VA RNA(II) is more effective than VA RNA(I) as an inhibitor of RNA helicase activity, Th ese data identify RNA helicase A and NF90 as cellular proteins with an affinity for dsRNA and other structured RNA molecules and suggest tha t their functions are subject to regulation by RNA ligands including V A RNA(II).