A comparison of poly (A)-associated RNA from synaptosomes and cytoplasmic subcellular fractions of rat brain.

Oligo(dT)-cellulose binding poly(A)-RNA from rat brain microsomes, mitochondria and synaptosomes was isolated and analysed. Synaptosomes and mitochondria appeared to contain a higher proportion of such RNA than microsomes. Poly(A)-RNA from the three fractions was then electrophoretically fractionated in two different gel systems. Mitochondrial and microsomal poly(A)-RNA presented different fractionation patterns. Synaptosomal poly(A)-RNA also presented a characteristic patterns of its own which could not be entirely explained as a mixture of the previous two. Its main feature was the presence of a prominent band with an SE value of around 7. Such species, absent in microsomes, was present as well in mitochondria but in smaller concentration. On the basis of the present evidence and of previous results, it appears that such 7 SE species, although a mitochondrial messenger RNA in origin, becomes accumulated in vivo into synaptic membranes.