[Isolation and analysis of brain-specific sequences from cDNA libraries for various segments of the human brain]

The cDNA libraries in gt10 were constructed from total poly(A)+RNA of human forebrain cortex, cerebellar cortex and medulla oblongata. We selected the clones which gave hybridization signal with brain cDNA only, or gave no signal from these libraries. Expression pattern and structure of two brain-specific clones Hfb1 from forebrain library and Hmob3 from medulla oblongata library were analyzed in detail. Hfb1 hybridized to two different transcripts (about 5 and 2 kb) from frontal cortex, but to a single (longest) from cerebellum. Hfb1 sequence includes 958 nucleotides. Comparison of Hfb1 with the Gene Bank revealed no homology with the sequences present in the Bank. At 3'-end there is poly(A) tail of 24 bases, there is the AATCAA sequence 55 nucleotides upstream which probably serves as a polyadenylation signal. However, AATCAA directs polyadenylation in vitro with very low efficiency. We found no open reading frame in the clone and this is in agreement with the data indicating that brain-specific RNAs has extremely long 3'-untranslated regions. Hmob3 was partially sequences. We compared its primary structure with the sequences from the Gene Bank and revealed no homology. Hmob3 expresses in different parts of human brain and in sceletal muscle but does not express in other tissues.