THE DIMERIZATION PACKAGING SEQUENCE IS DISPENSABLE FOR BOTH THE FORMATION OF HIGH-MOLECULAR-WEIGHT RNA COMPLEXES WITHIN RETROVIRAL PARTICLES AND THE SYNTHESIS OF PROVIRUSES OF NORMAL STRUCTURE

Retroviral particles contain a dimer of two genomic RNA molecules, lin ked by noncovalent intermolecular bonds. Studies by electron microscop y of viral RNA extracted from virions as well as in vitro studies have implicated a sequence, designated the dimer linkage sequence (DLS), i n the dimerization process. The DLS has been localized within a short region encompassing the Psi packaging sequence, between nucleotides 21 2 and 563 for the Moloney murine leukemia retrovirus (MoMLV) RNA. In t his report, we show that viral RNAs lacking both the DLS and Psi packa ging sequences-and even an RNA lacking the first 6,537 nucleotides of MoMLV-can assemble within retroviral particles as high-molecular-weigh t, slow-migrating, heat-sensitive complexes closely related to those o bserved for wild-type viral RNAs. Furthermore, we show that proviruses of normal structure are generated upon infection of test cells with r etroviral particles which contain the DLS/Psi-deleted viral RNAs. Thes e observations demonstrate that the DLS and Psi packaging sequences ar e not essential in cis to form a functional RNA complex for reverse tr anscription and integration.