Six major cone proteins of 40S hn RNP exist as three tetramers which bind pre-MRNA during transcription and package 700 nucleotide lengths of RNA into a repeating array of regular particles. It is likely that this phenomenon play and important role in preventing heteroduplex formation during transcription and that it forces the numerous transcripts of active genes into a manageable conformation. Clearly the packaging mechanism must accommodate all RNA processing events. Several lines of evidence demonstrate that the core proteins alone do not pass the necessary information to direct particle assembly at sequence specific sites in vitro, thus the reactive sites involved in splicing may not be packaged in hn RNP in the same way as the bulk of the RNA. Attempts will be made to provide a topological view of RNA and proteins in monoparticles and to determine if mechanisms exist to phase the assembly of hn RNP in a splicing consistent manner. A large number of ultrastructural and biochemical findings now argue convincingly that pre-MRNA is packaged during transcription into a repeating array of regular ribonucleoproteins particles and there is considerable evidence that splice site recognition, spliceosome assembly, larial formation, excision and legations all occur while RNA exists in a highly packaged state. Recent work by Dr. Le Stourgeon now makes possible mechanistic understanding of RNA processing.//
