PRIMARY STRUCTURE, NEURAL-SPECIFIC EXPRESSION, AND DENDRITIC LOCATIONOF HUMAN BC200 RNA

Primate BC200 RNA is a 200-nucleotide-long, nontranslatable RNA that i s prevalently expressed in the nervous system. We have determined the primary structure of human BC200 RNA, using cDNA cloning and PCR techn iques. BC200 RNA can be subdivided into three structural domains. The 5' region is homologous to Alu repetitive elements that are found in h igh copy numbers in primate genomes. The central part of BC200 RNA is characterized by a high percentage of A-residues, with a few intersper sed other nucleotides. The 3' sequence is unique to BC200 RNA and show s no apparent similarity with known human DNA sequences. Sequence simi larity with rodent BC1 RNA is limited to several short elements, and B C1/BC200 sequence comparisons indicate that the two genes have evolved via separate phylogenetic routes. Probes directed against the 3' uniq ue part of BC200 RNA detected a single band corresponding to approxima tely 200 nucleotides on RNA blots. This band was identified only with RNA isolated from human brain, not with RNA from non-neural organs suc h as lung or kidney. In situ hybridization to selected areas of the hu man nervous system showed that BC200 RNA is expressed by a subpopulati on of neurons that is analogous to the BC1 RNA-expressing subset of ne urons in the corresponding areas of the rat nervous system. Moreover, like rat BC1 RNA, human BC200 RNA was localized to dendrite-rich neuro pil areas, for example, in the inner plexiform layer of the retina. Th ese results indicate that BC1 RNA and BC200 RNA, although of different evolutionary pedigree, may play analogous functional roles, in rodent s and primates, respectively, in somatodendritic domains of nerve cell s.