To identify novel antiapoptotic proteins encoded by DNA viruses, we searched viral genomes for proteins that might interfere with Fas and TNFR1 apoptotic signaling pathways. We report here that equine herpesvirus type 2 E8 protein and molluscum contagiosum virus MC159 protein both show sequence similarity to the death effector domains (DEDs) of the Fas͞TNFR1 signaling components FADD and caspase-8. Yeast two-hybrid analysis revealed that E8 protein interacted with the caspase-8 prodomain whereas MC159 protein interacted with FADD. Furthermore, expression of either E8 protein or MC159 protein protected cells from Fasand TNFR1-induced apoptosis indicating that certain herpesviruses and poxviruses use DED-mediated interactions to interfere with apoptotic signaling pathways. These findings identify a novel control point exploited by viruses to regulate Fas-and TNFR1-mediated apoptosis.

Chemogenetic characterization through in vitro evolution combined with whole-genome analysis can identify antimalarial drug targets and drug-resistance genes. We performed a genome analysis of 262 Plasmodium falciparum parasites resistant to 37 diverse compounds. We found 159 gene amplifications and 148 nonsynonymous changes in 83 genes associated with drug-resistance acquisition, where gene amplifications contributed to one-third of resistance acquisition events. Beyond confirming previously identified multidrug-resistance mechanisms, we discovered hitherto unrecognized drug target–inhibitor pairs, including thymidylate synthase and a benzoquinazolinone, farnesyltransferase and a pyrimidinedione, and a dipeptidylpeptidase and an arylurea. This exploration of the P. falciparum resistome and druggable genome will likely guide drug discovery and structural biology efforts, while also advancing our understanding of resistance mechanisms available to the malaria parasite.

We identified and cloned a novel human protein that contains FADD/Mort1 death effector domain homology regions, designated FLAME-1. FLAME-1, although most similar in structure to Mch4 and Mch5, does not possess caspase activity but can interact specifically with FADD, Mch4, and Mch5. Interestingly, FLAME-1 is recruited to the Fas receptor complex and can abrogate Fas/TNFR-induced apoptosis upon expression in FasL/ tumor necrosis factor-sensitive MCF-7 cells, possibly by acting as a dominant-negative inhibitor. These findings identify a novel endogenous control point that regulates Fas/TNFR1-mediated apoptosis.Several members of the caspase family of proteases (1) have been implicated as key regulators of programmed cell death or apoptosis (2, 3). The proapoptotic caspases can be divided into two groups: those with a large prodomain such as ICH-1 (caspase-2), Mch4 (caspase-10), Mch5/MACH/FLICE (caspase-8) and Mch6/ICE-Lap-6 (caspase-9) and those with a small prodomain such as CPP32/YAMA/Apopain (caspase-3), Mch2 (caspase-6), and Mch3/ICE-Lap-3 (caspase-7). Caspases with large prodomains are probably the most upstream caspases (4, 5). They are recruited by several death-signaling receptors that belong to the TNFR family (6) through interactions of their prodomain with the receptor-interacting adaptor molecules FADD/Mort1 (7, 8) or CRADD/RAIDD (5, 9). For example, the prodomains of Mch4 and Mch5 contain two tandem regions that show significant homology with the N-terminal death effector domain (DED) 1 of FADD (10 -12). Engagement of Fas/TNFR1 results in recruitment of FADD to the receptor complex (13), which presumably triggers activation of the caspase apoptotic pathway through interaction of its DED with the corresponding motifs in the prodomain of Mch5 and probably Mch4. CRADD presumably functions like FADD by recruiting ICH-1 to the Fas/TNFR1 complex, through interaction of its N-terminal domain with the corresponding motif in the prodomain of ICH-1 (5, 9). Thus, the prodomains of caspases function to physically link the death receptors to the downstream caspase activation pathway.In our efforts to characterize novel apoptotic/anti-apoptotic molecules that contain FADD-DED homology regions, we have identified a human molecule designated FLAME-1 (FADD-like antiapoptotic molecule) that is structurally related to Mch4 and Mch5. We show that FLAME-1 is recruited to the Fas signaling pathway through interaction with FADD. Interestingly, FLAME-1 can block Fas/TNFR1-induced apoptosis but not UV-induced apoptosis.

A STE20/p65pak homolog was isolated from fission yeast by PCR. The pak1+ gene encodes a 72 kDa protein containing a putative p21‐binding domain near its amino‐terminus and a serine/threonine kinase domain near its carboxyl‐terminus. The Pak1 protein autophosphorylates on serine residues and preferentially binds to activated Cdc42p both in vitro and in vivo. This binding is mediated through the p21 binding domain on Pak1p and the effector domain on Cdc42p. Overexpression of an inactive mutant form of pak1 gives rise to cells with markedly abnormal shape with mislocalized actin staining. Pak1 overexpression does not, however, suppress lethality associated with cdc42‐null cells or the morphologic defeat caused by overexpression of mutant cdc42 alleles. Gene disruption of pak1+ establishes that, like cdc42+, pak1+ function is required for cell viability. In budding yeast, pak1+ expression restores mating function to STE20‐null cells and, in fission yeast, overexpression of an inactive form of Pak inhibits mating. These results indicate that the Pak1 protein is likely to be an effector for Cdc42p or a related GTPase, and suggest that Pak1p is involved in the maintenance of cell polarity and in mating.