Polyadenylic Acid‐containing Rna From Rat Brain Synaptosomes

Abstract

Abstract— Synaptosomal RNA of rat brain was labelled in vivo by intracranial injection of tritiated uridine. The change in the specific activity of this material with time was similar to that of polysomal RNA. The percent of the radioactive synaptosomal RNA which bound to oligo(dT)‐cellulose columns decreased with time after intracranial labelling. The percent of the total synaptosomal RNA which bound to oligo(dT)‐cellulose was greater than that of polysomes. The length of the polyadenylate (poly(A)) sequence of synaptosomal RNA was approximately one‐half that of polysomal RNA, and about the same as that from mitochondria. Investigation of synaptosomal RNA using sucrose gradients and polyacrylamide gel electrophoresis indicated that there were several distinct species present, and that they were similar to those from the mitochondria. The poly(A)‐containing RNA isolated from synaptosomes stimulated the incorporation of radioactive leucine into TCA‐precipitable material in a cell‐free protein synthesis system. Isolation of RNA from subsynaptosomal components indicated that most, if not all, of the synaptosomal messenger activity was localized in the synaptic mitochondria.

Studies on Polyadenylic Acid‐Containing RNA from Developing Nervous System of the Chicken the

“…The in vitro studies carried out with both brain and sciatic nerve indicate that tissues of younger animals appear to synthesize RNA possessing a greater proportion of poly(A)+ sequences than did RNA synthesized in tissues of post-hatching chicks ( Table 3). These results are similar to those obtained for rat and mouse brain in vitro and in vivo (DeLarco and Guroff, 1972;Banks and Johnson, 1973;DeLarco et al, 1975;Berthold and Lim, 1976~). However, in vivo results carried out with brain tissue in the present investigation indicate a different trend ( Table 4).…”

Local Gene Expression in Axons and Nerve Endings: The Glia-Neuron Unit

“…Synthesis of synaptosomal RNA was examined in young rats after the intracranial injection of [ 3 H]uridine and [ 3 H]adenosine (69). At the earliest time examined (1 h), the specific activity of synaptosomal RNA was approximately half that of mitochondrial RNA and one-fourth that of polysomal RNA.…”

“…In early studies (14), cell body mitochondria and intrasynaptosomal mitochondria from rat brain were shown to contain similar concentrations of DNA (6.3 g/mg protein) and RNA (12-13 g/mg protein), but higher concentrations of RNA were present in synaptosomal membrane fractions (up to 21 g/mg protein). In later studies, extramitochondrial synaptosomal RNA was identified as rRNAs and 4S RNA that were consistently attributed to contaminating elements (59,69,89,211). Nonetheless, in addition to mitochondrial RNAs and typical cytoplasmic rRNA (18S, 28S) and small RNA (4S, 5S), the synaptosomal fraction of adult rat brain contained two RNA components that were absent in mitochondrial and microsomal fractions (59, 60).…”

“…It is of interest that in experiments on young rats, brain synaptosomes and mitochondria were reported to contain a much higher proportion of poly (A) ϩ RNA than polysomes (ϳ18% compared with 7%), and to display a similar capacity to direct protein synthesis in a cell-free translation system (69). Synaptosomal membranes and synaptosomal mitochondria had a similar content of poly (A) ϩ RNA (15.5 and 13.5%, respectively), but the capacity to direct protein synthesis in a cell-free system was much lower for the RNA prepared from synaptosomal membranes.…”

“…The major component of synaptosomal poly(A) corresponded to 84 nt, while that of the polysomal fraction was twice as large (169 nt). [Modified from DeLarco et al (69).] same token, glial cells were once named "trophocytes."…”