Separation and sequence of the 3' termini of M double-stranded RNA from killer yeast.

Four subspecies of M double-stranded RNA from a killer strain of Saccharomyces cerevisiae were isolated. Each subspecies were susceptible to heat cleavage, presumably at an internal 190 base pair A,U-rich region, generating two discrete fragments corresponding to each side of the A, U-rich region. Enzymatic and chemical RNA sequence analysis defined the 3'-terminal 175 bases for the larger fragment (M-1) and 231 bases for the smaller fragment (M-2). All four subspecies of M have identical size and 3'-terminal sequences. Potential translation initiation codons are present on the corresponding 5' termini of both fragments, and a possible 18S ribosomal RNA binding site is also present on the 5' terminus of M-1. Stem and loop structures for the 5' and 3' termini of M-1 may function as recognition sites for replication, transcription, and translation.