Demonstration of RNA-dependent DNA polymerase activity in non-disrupted type D-retravirus particles after treatment with EDTA.

The type D-retraviruses PMF virus (PMFV) and Mason-Pfizer moneky virus (MPMV) show RNA-dependent DNA polymerase (revertase) activity after treatment of the nondisrupted virions with the chelating agent ethylenediaminetetraacetate (EDTA). In the range of 1 to 5 mM, the effect is dependent on the concentration of EDTA. As compared with Nonidet P40 disrupted particles treatment of PMFV with EDTA results in a revertase activity of about 65%. Simultaneous addition of Mg- or Ca-ions prevents the EDTA effect. Other divalent cation-binding agents (o-phenathroline, thiosemicarbazide) do not induce an EDTA-like effect. It is suggested that EDTA chelates divalent ions responsible for the structural organization of the viral membrane which, after chelation, gets permeable for the exogenous revertase template.