Presence of multimple species of polypeptides immunologically related to transcription factor TFIIIA in adultXenopus tissues

Transcription of 5S RNA gene in Xenopus oocytes requires a 38 kDa transcription factor TFIIIA, which interacts with the 50 bp internal control region of the gene. We looked for TFIIIA-like polypeptides in the extracts of adult Xenopus tissues on the basis of their antigenic cross-reactivity to anti-TFIIIA antibody. Several species of polypeptides ranging from 30 to 50 kDa were found in kidney, stomach, liver and testis. Although these polypeptides reacted specifically to anti-TFIIIA antibody, proteolytic peptide mapping of three representative ones did not reveal any mutual similarities. They also seemed to be distinct from TFIIIA. Possible functions of these proteins are discussed.