WILD-TYPE AND MUTANT HIV TYPE-1 NUCLEOCAPSID PROTEINS INCREASE THE PROPORTION OF LONG CDNA TRANSCRIPTS BY VIRAL REVERSE-TRANSCRIPTASE

HIV-1 nucleocapsid, p7, contains two retroviral zinc fingers, which ar e both necessary for efficient packaging of geriomic RNA and infectivi ty. The nucleocapsid protein is bound tightly to genomic RNA in the ma ture virion, In this study, the effect of p7 on polymerization of nasc ent cDNA by viral reverse transcriptase (RT) was examined, An 874-base RNA of HIV-1 was synthesized and used as a template in RT assays with varying concentrations of intact p7, mutants of p7 that have transpos ed or repeated zinc fingers, and several different peptides that repre sent various structural regions of p7, Results indicate that at greate r than or equal to 50% saturation of p7-binding sites, with p7, there is up to a 90% reduction in total cDNA synthesis, as measured by nucle otide incorporation, However, the cDNA products that are made are almo st exclusively full length, Three zinc finger mutants exhibited effect s similar to those of wild-type p7, N-terminal and C-terminal halves o f p7 inhibited total nucleotide incorporation, but also inhibited synt hesis of long cDNA products by RT, In the absence of p7 an array of sh ort transcripts (<200 bases) was produced by RT, These studies show th at full-length p7 is necessary to increase the proportion of long cDNA transcripts produced by RT, The relative position of the two zinc fin gers is not critical for this effect.