Characterization of the dimerization state and splicing of viral RNA. (A) Dimerization analysis of virion RNA. Virion RNAs of different proviral constructs were separated on a native agarose gel and characterized by Northern analysis. Dimer and monomer are indicated on the right side of the blot. Results are representative of two sets of experiments. (B) Compensatory mutations in gag did not affect RNA dimerization. Amounts of dimeric and monomeric RNA were quantified by densitometry, and the percentages of dimers for each construct present in the virion calculated. Means and SD of two independent experiments are shown. (C) Deletion of SL1 did not affect the splicing of HIV-1 RNAs. 293T cells were transfected with the HIV-1 constructs. Total RNA was isolated 48 hrs post-transfection and reverse-transcribed. The 4-kb singly spliced HIV-1 RNAs were amplified from cDNA and separated on an agarose gel. The SL1 deletion resulted in a population of smaller mRNAs than those observed for the wild-type HIV-1. Sequence analysis verified the identity of the products and showed that the deletion mutants had the same splicing patterns as the wild-type virus.