Fig. 6

TCR signaling pathways in primary CD4⁺ T cells contribute to the stimulation of proviral HIV-1 transcription. RasGRP1-Ras-Raf-MEK-ERK1/2 and PI3K-mTORC2-AKT-mTORC1 complement one another in stimulating the posttranscriptional synthesis of CycT1, leading to P-TEFb assembly. The exact mechanisms by which ERK and mTORC1 stimulate CycT1 translation are yet to be fully delineated. Although intracellular calcium release, the activation of PKC-θ and the JNK MAPK pathway are dispensable for the formation of P-TEFb, they are likely to mediate the recruitment of RNA polymerase II (RNAP II) to proviral HIV and thus its eventual phosphorylation by P-TEFb to stimulate processive transcription elongation