Formation of a ribonucleoprotein complex of mouse hepatitis virus involving heterogeneous nuclear ribonucleoprotein A1 and transcription-regulatory elements of viral RNA

The heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) specifically bind s to two transcription-regulatory elements, i.e:, the leader and intergenic sequence, of the negative-strand(template-strand) RNA of mouse hepatitis v irus (MHV) and may play a role in viral RNA transcription. Previous studies based on the defective-interfering RNAs of MHV suggested that these two RN A elements may interact with each other during transcription, although they do not have complementary sequences. In this study, we showed by an in vit ro reconstitution assay that hnRNP Al could mediate the formation of an RNP complex involving these two RNA elements. Both the RNA-binding domains and protein-interacting domain of hnRNP Al contributed to the efficient format ion of the RNP complex; however, the presence of the two RNA-binding domain s alone, without the protein-interacting domain, also resulted in some RNP formation. Omission of hnRNP Al in the reconstitution reaction abolished th e RNP formation, and mutations of the IG sequences significantly inhibited the RNP formation. These findings suggest that the two cis-acting transcrip tion-regulatory sequences of MHV RNA can interact with each other through t he formation of an RNP complex involving a cellular protein hnRNP Al. This RNP complex may participate in MHV RNA transcription, (C) 1999 Academic Pre ss.