HIV-1 gp120 induces the activation of both c-fos and c-jun immediate-earlygenes in HEL megakaryocytic cells

We have previously demonstrated that the addition in culture of recombinant HIV-1 IIIB envelope gp120 affects the survival/growth of pluripotent haemo poietic progenitors, and, in particular, of those committed towards the meg akaryocytic lineage, To characterize some of the molecular mechanisms invol ved in this phenomenon, we investigated the expression of members of the ac tivating protein-1 (AP-1) complex in the HEL megakaryoblastic cell line. Fo llowing the treatment of HEL cells with recombinant IIIB envelope gp120, we noticed: (i) increased levels of endogenous c-fos and c-jun mRNA and prote ins, (ii) activation of both c-fos and c-jun promoters, and (iii) a very ra pid stimulation of a MAPK/ERK pathway.