Uukuniemi virus contains an RNA polymerase.

An RNA-dependent RNA polymerase activity has been found associated with Uukuniemi virions. The enzyme activity is expressed only after disrupting the virions with the nonionic detergent Triton X-100 and is absolutely dependent on Mn2+, whereas Mg2+ is not required, a finding that distinguishes this polymerase from those of other enveloped minus-strand RNA viruses. Within the range pH 7.2 to 8.5 no distinct optimum was found. The optimum temperature was between 37 and 40 C. The reaction was not inhibited by actinomycin D, rifampin, or DNase, whereas RNase was completely inhibitory. The partially RNase-resistant product consisted of rather small-sized RNA, which contained sequences complementary to Uukuniemi virus RNA as shown by hybridization to the template L, M, and S RNA species of Uukuniemi virus.