Mitochondrial HSP70, HSP40, and HSP60 bind to the 3′ untranslated region of the Murine hepatitis virus genome

We have previously shown that mitochondrial-aconitase binds specifically to the 3′ terminal 42 nucleotides of the Murine hepatitis virus (MHV) RNA along with three additional proteins of 70, 58 and 40 kDa to form a stable RNA-protein complex. Supershift and western blot assays have identified these three proteins as mitochondrial HSP70 (mtHSP70), HSP60, and HSP40. A series of co-immunoprecipitation assays have established that these four MHV RNA binding proteins are associated, even in the absence of MHV RNA. However, the presence of a synthetic RNA containing the sequence bound by these four proteins does increase the amount of co-precipitated protein, in particular the amount of HSP60 which is brought down with antibodies directed against HSP40 and mtHSP70. We have provided evidence for the interaction of these four proteins with the 3′ end region of MHV RNA in infected cells by a series of immunoprecipitation RT-PCR assays. We believe it is likely that MHV RNA interacts with m-aconitase prior to its import into mitochondria in cooperation with extra-mitochondrial mtHSP70, HSP60, and HSP40.