Polytranscripts of Sendai virus do not contain intervening polyadenylate sequences

Discrete high-molecular-weight RNA species with the properties of polytranscripts were observed in poly(A)-rich RNA extracted from Sendai virus-infected cells. These RNA species were virus specific, being synthesized in the presence of actinomycin D, but not seen in uninfected cells. They were not genome or antigenome fragments, since they were not encapsidated, as shown by their destruction when ribonuclease was added to cell homogenates and by their absence from the RNA fractions that did not bind to oligo(dT)-cellulose. Two lines of evidence indicated that the gene-specific regions of these polytranscripts were not linked by poly(A) sequences, but were faithful copies of virus genomic RNA sequences at gene boundaries. First, a small cDNA clone obtained by reverse transcription of poly(A)-rich RNA species from infected cells contained 90 bases from the 5' terminus of the gene for the P protein and about 600 bases from the 3' end of the downstream gene, which specifies the M protein, the entire cloned sequence being an accurate complement of the genomic RNA. Second, dideoxynucleotide sequencing of poly(A)-rich RNA species primed by virus gene-specific oligodeoxynucleotides revealed read-through products of transcription containing no detectable poly(A). If Sendai virus polytranscripts are intermediates in the production of monocistronic viral mRNAs by a cleavage process, and poly(A) sequences do not link the mRNAs, polyadenylation would have to follow the cleavage step; it seems more likely that these polytranscipts are aberrant transcription products generated by occasional termination failure in a stop-start mechanism of transcription.