Activation of Host Translational Control Pathways by a Viral Developmental Switch
Figure 5
Phosphorylated eIF4E accumulates following KSHV lytic reactivation.
A. KSHV reactivation stimulates eIF4E phosphorylation. TREx BCBL1 or TREx BCBL1-RTA cells either untreated (−) or treated (+) with TPA+DOX were collected at the indicated times post-induction. Cytosolic lysates were fractionated by IEF and analyzed by immunoblotting using anti-eIF4E. The arrowheads indicate the different mobilities of the phospho- vs unphosphorylated eIF4E forms [respectively denoted as 4E–P and 4E]. B. Activation of the eIF4G-bound kinase Mnk1 by ERK and p38 in response to diverse stimuli. Active Mnk1 phosphorylates eIF4E when both kinase (Mnk1) and substrate (eIF4E) are bound to eIF4G. C. KSHV lytic reactivation activates ERK. TREx BCBL1 or TREx BCBL1-RTA cells were treated with TPA, DOX or TPA+DOX for 48 h. Total protein was subsequently isolated, fractionated by SDS-PAGE and analyzed by immunoblotting using antibodies specific for RTA or ERK [phospho (denoted as ERK P) vs. total ERK]. RhoGDI: loading control. D. p38 is activated in latently-infected cells, and remains active upon KSHV lytic reactivation. Same as in B, except the antisera was specific for phospho- (denoted as p38 P) or total p38.