Further characterization of an MSP-1-derived transcription particle (transcripton) using monoclonal and polyclonal antibodies.

A native transcription particle (transcripton) derived from Novikoff nucleoli by digestion with MSP-1 was isolated and characterized. Various monoclonal and polyclonal antibodies were used to determine their subsequent effect upon the Native transcription particle (NTP) transcription assay. The NTP was enriched in RNA polymerase 1 and some/all of its factors, including a 145 kD protein, a 345 kD protein, and topoisomerase 1 (110 kD). Using Western analysis monoclonal antibody made against the transcripton recognized a 55 kD protein, which immunolocalized to nucleolar and nuclear membrane structures. This antibody caused transcriptional inhibition of the transcripton in subsequent assays as did the antibody to the 345 kD protein. The monoclonal antibody against the 145 kD protein had no effect on transcription. When antibody to topoisomerase 1 was included in the assay, enhancement of transcription was observed.