A SHORT AUTOCOMPLEMENTARY SEQUENCE IN THE 5'-LEADER REGION IS RESPONSIBLE FOR DIMERIZATION OF MOMULV GENOMIC RNA

Previous work has shown that a region of Moloney murine leukemia virus (MoMuLV) RNA located between nucleotides 280 and 330 in the PSI regio n (nt 215-565) is implicated in the dimerization process. We show with a deletion from nucleotides 290-299 in PSI RNA transcripts and throug h an antisense oligonucleotide complementary to nucleotides 275-291 th at the 283-298 region is involved in RNA dimer formation in vitro. In an attempt to further characterize the mechanism of dimer formation, a series of short RNA transcripts was synthesized which overlapps the P SI region of MoMuLV RNA. The dimerization of these RNAs is temperature dependent. The predicted secondary structure of the 278-303 region, a s a function of temperature, reveals that this sequence is able to ado pt two conformations: (1) the U(288)AGCUA(293) sequence in a loop (2) part of the same nucleotides implicated in a stem. These results, toge ther with thermodynamic analysis, strongly suggest that (1) the loop c onformation of the UAGCUA sequence modulates the relative amount of RN A dimer and (2) a 16 bp long Watson-Crick base pairing is involved in RNA dimer formation. We propose that loop-loop recognition via the U(2 88)AGCUA(293) sequence leads to a stable structure induced by a stem-l oop opening. Furthermore, our results do not support purine quartet fo rmation as necessary for the dimerization of the 5' leader MoMuLV RNA.