Biphasic switch of suppression and recovery during single-step replication.
(A) Workflow of HPG pulse-labeling for the earliest analysis of translation during single-step replication. (B) Cells were synchronously infected (MOI 10) with HSV-1[KOS] and analysed for newly synthesised proteins and steady state accumulated ICP4 (red) at either 1 hr p.i. or 4 hr p.i. Cell classes with respect to protein synthesis levels are labeled A, B, or C as discussed in the text. NPD formation (arrowheads) and increased ICP4 levels are shown in a class C cell. Translation levels were colour coded with yellow representing cells reduced to 30% or below the maximum observed and pink representing cells above this level. (C) Vero cells were mock-infected or infected as above with the indicated strains of HSV and labeled either at 1 hr p.i. or 4 hr p.i. for 30 min. Cells were analysed as described for S1 Fig with newly synthesised protein profiles in the left hand panel and total protein profile of the identical gel in the right hand panel. (D) Simulation of an early oscillation in protein synthesis (though simulation applies to any output), with time after infection. The Y-axis represents levels of protein synthesis (% of uninfected) and the x-axis represents time (min). The model shows a hypothetical outcome where protein synthesis declines to zero and returns to a definable percentage of starting level (90% in this example), within a cycle time that can be also be set (30 min in the left hand panel). Thereafter protein synthesis declines at an exponential rate with a t1/2 that can also be set. However infection in a population is not instantaneous and it takes a finite amount of time for all cells to become infected. This is represented by an “asynchrony rate”, assumed to be linear for simplicity, and can also be varied in the simulation. Here all cells will be infected by 45 min at a rate of 5% of the population, every 2.25 min. (In principle, there could be a single curve for every cell in a population e.g. 106 curves, but this is impractical for demonstration purposes). Each black curve therefore represents 5% of the population, there are 20 such curves and the oscillating cycle is initiated in all cells by 45 min. The outcome for each curve (i.e. each 5%) is shown, together with the total output, at any one time, averaged across the population (red line). Even where the output could be sample instantaneously, the averaged output declines by only a modest amount, and would not reflect the reality of a decline to zero in each cell. In the example in the right hand panel, the cycle time has been lengthened to 40 min with other parameters the same. Even here, the total, maximal decline is still less than two fold.
