The inhibition of transcription by
RNA polymerase III in poliovirus-infected cells was studied. Experiments utilizing two different cell lines showed that the initiation step of transcription by
RNA polymerase III was impaired by
infection of these cells with the virus. The observed inhibition of transcription was not due to shut-off of host cell
protein synthesis by poliovirus. Among four distinct components required for accurate transcription in vitro from cloned
DNA templates, activities of
RNA polymerase III and
transcription factor TFIIIA were not significantly affected by
virus infection. The activity of
transcription factor TFIIIC, the limiting component required for transcription of
RNA polymerase III genes, was severely inhibited in infected cells, whereas that of
transcription factor TFIIIB was inhibited to a lesser extent. The sequence-specific
DNA-binding of
TFIIIC to the adenovirus VA1 gene internal promoter, however, was not altered by
infection of cells with the virus. We conclude that (i) at least two
transcription factors,
TFIIIB and
TFIIIC, are inhibited by
infection of cells with poliovirus, (ii) inactivation of
TFIIIC does not involve destruction of its
DNA-binding domain, and (iii) sequence-specific
DNA binding by
TFIIIC may be necessary but is not sufficient for the formation of productive transcription complexes.