Hence, the profile of inappropriately processed and polyadenylated U14 forms that accumulate in rrp6Δ cells is affected by concomitant mutations of the Ccr4-Not complex.
This effect was independent from the phosphorylation of the T187 since it was not rescued by the concomitant mutation of T187 in Alanine and were confirmed using DNA transfection instead of adenoviral transduction using 3 different cell lines (Figure S1 and Figure 1B).
Confirmation of this was obtained by analysis of the sarA/alsSD double mutant UAMS-13000), which demonstrated that concomitant mutation of alsSD and sarA had no further impact on the production of acetoin (data not shown) but did reduce biofilm formation even by comparison to an alsSD mutant (p<0.001) (Fig. 4).
In contrast, concomitant mutation of sarA and nuc significantly enhanced biofilm formation by comparison to the sarA mutant.
Although mutation of sarA in RN6390 had relatively little impact of either of these phenotypes, concomitant mutation of sarA and agr in RN6390 reversed both phenotypes by comparison to the corresponding agr mutant (Fig. 6).
More importantly, concomitant mutation of nuc in a sarA mutant UAMS-14777) enhanced biofilm formation by comparison to the sarA mutant (p<0.001) (Fig. 7).
Concomitant mutation of sarA and agr resulted in increased nuclease activity in all strains even by comparison to the isogenic sarA mutant (Fig. 11).
Additionally, mutation of sigB in LAC limited biofilm formation even in flow cells, and concomitant mutation of agr reversed this effect [8].
The Ppp1r15b null phenotype is rescued by a concomitant mutation, S51A, which blocks phosphorylation of eIF2αS51, implicating the PPP1C PPP1R15B partnership to dephosphorylate eIF2α as responsible for the phenotypic presentation in this mouse model (21).
Notably, the phenotypes in Ppp1r15a/Ppp1r15b null and Ppp1r15b null mice are rescued by the introduction of a concomitant mutation in eIF2α, which prevents phosphorylation (S51A), suggesting that misregulated phosphorylation is predominantly responsible for the phenotypes observed (21).
