Attenuation and modulation of mRNA secondary structure in a feedback control system regulating SV40 gene expression.

Alternative secondary structures can be predicted for the initial 94 nucleotides synthesized from the major transcription initiation site of SV40 late RNA: a transcription-termination conformation results in the production of aborted RNA and a readthrough conformation leads to the synthesis of the primary SV40 late RNA. In the cytoplasm similar alternative conformations can be predicted for the initial nucleotides at the 5' ends o both the major 16S and 19S late mRNAs. In one of these alternative conformations the AUG initiation codon of the leader protein (agnoprotein) is sequestered and not available for ribosome binding. In the alternative conformation the same AUG is accessible for ribosome binding. We suggest that these mutually exclusive conformations are fundamental elements in a transcription and translation feedback control mechanism regulating the synthesis of 16S and 19S mRNA in the nucleus and the translation of their encoded proteins in the cytoplasm.