Arias et al. BMC Genomics 2011, 12:390 http://www.biomedcentral.com/1471-2164/12/390 Page 6 of 17 Figure 3 Interaction network among gene products whose disruption causes Slt2 activation. Physical and functional interactions were identified computationally using the STRING web resource (8.3 version). Gene products are represented as nodes, shown as filled circles colored according to their functional classification (see Table 1). Interactions are represented as node-connecting edges, shown as lines. Stronger associations are represented by thicker lines. Genes/Proteins with no reported interaction are not shown. In S. cerevisiae, mannosyltransferases are highly redun- dant, being included in different protein families [7,50]. The identification of the abovementioned proteins is indicative of their specific importance in cell wall homeostasis. Within the group of mutants involved in cellular sig- naling, we have identified several well-known negative regulators of Slt2 activity, such as the Rho1 GTPase acti- vators Sac7 and Bem2, and protein phosphatases Sit4 and Msg5, which negatively regulate the pathway acting on Pkc1p and Slt2p, respectively [51,52]. We also identified Rom2 in spite of being an activator (Rho1 GEF) of the CWI pathway and the protein kinase Ypk1, a regulator linking sphingolipid signaling and CWI pathway [53]. The effect on Slt2 activation in a rom2Δ strain has previously been described [54]. These authors hypothe- sized that rom2Δ mutants have a defective cell wall due to a decreased activity of the CWI pathway, and this alteration may triggers Slt2 activation through Rom2- independent mechanisms. The singling out of these mutants further validates our screening for discovering novel potential regulators of the CWI pathway. This is the case of Nbp2, Ksp1, Fpk1, Mog1 and Skn7. Nbp2 acts as a negative regulator of the HOG pathway by recruiting Ptc1 phosphatase to Hog1 [55], and has been involved in cortical ER inheritance via Slt2 [56], the protein kinase Ksp1 has recently been linked to filamentous growth in haploid yeast cells [57], and Fpk1 (flippase kinase 1) regu- lates phospholipid membrane translocation [58]. Skn7 is a multifunctional transcription factor, as reflected by its