Nucleotide sequence of small polyadenylated B2 RNA

Small poly(A)-containing RNA molecules which hybridize to the ubiqui tous short r e p e t i t i v e sequence B2 and which are t ransc r ibed by RNA polymerase I I I have been i d e n t i f i e d i n the cytoplasm of mouse c e l l s. Here, we describe the s t ruc tu re of t h i s small B2 RNA. A cDNA l i b r a r y was prepared from low-mole-cular-weight cytoplasmic poly(A)+RNA i s o l a t e d from Ehr l ich ca r-cinoma c e l l s and the clones which hybridized to B2 sequence were se l ec t ed. The clones were sequenced and shown to contain B2 sequences followed by a poly(Aj t r a c t. The sequences of the cloned B2 RNAs d i f fe ren t from each other by 3-10%, being s imi-l a r i n t h i s respec t to genomic B2 copies. Thus, B2 SNA i s t ransc r ibed from many d i f fe ren t B2 sequences in the genome. The 5 '-ends of B2 RNA at l e a s t i n most molecules coincide with the beginning of B2 genomic sequence. The poly(A) segments loca ted a t the 3 '-end of small B2 RNA are the same s ize as in rnRNA mo