Roles and interactions of the specialized initiation factors EIF4E2, EIF4E5, and EIF4E6 in Trypanosoma brucei: EIF4E2 maintains the abundances of S-phase mRNAs.

Trypanosoma brucei has six versions of the cap-binding translation initiation factor EIF4E. We investigated the functions of EIF4E2, EIF4E3, EIF4E5, and EIF4E6 in bloodstream forms. We confirmed the protein associations previously found in procyclic forms and detected specific copurification of some RNA-binding proteins. Bloodstream forms lacking EIF4E5 grew normally and differentiated to replication-incompetent procyclic forms. Depletion of EIF4E6 inhibited bloodstream-form trypanosome growth and translation. EIF4E2 copurified only the putative RNA-binding protein SLBP2. Bloodstream forms lacking EIF4E2 multiplied slowly, had a low maximal cell density, and expressed the stumpy-form marker PAD1 but showed no evidence for enhanced stumpy-form signaling. EIF4E2 knock-out cells differentiated readily to replication-competent procyclic forms. EIF4E2 was strongly associated with a subset of mRNAs that are maximally abundant in the S-phase, and these all had decreased abundances in EIF4E2 knock-out cells. Three EIF4E2 target mRNAs are also bound and stabilized by the Pumilio domain protein PUF9. Yeast 2-hybrid results suggested that PUF9 interacts directly with SLBP2, but PUF9 was not detected in EIF4E2 pull-downs. We speculate that the EIF4E2-SLBP2 complex might interact with its target mRNAs, perhaps via PUF9, only early during G1/S, stabilizing the mRNAs in preparation for translation later in S-phase or in early G2.

The EIF4E1-4EIP cap-binding complex of Trypanosoma brucei interacts with the terminal uridylyl transferase TUT3.

Most transcription in Trypanosoma brucei is constitutive and polycistronic. Consequently, the parasite relies on post-transcriptional mechanisms, especially affecting translation initiation and mRNA decay, to control gene expression both at steady-state and for adaptation to different environments. The parasite has six isoforms of the cap-binding protein EIF4E as well as five EIF4Gs. EIF4E1 does not bind to any EIF4G, instead being associated with a 4E-binding protein, 4EIP. 4EIP represses translation and reduces the stability of a reporter mRNA when artificially tethered to the 3'-UTR, whether or not EIF4E1 is present. 4EIP is essential during the transition from the mammalian bloodstream form to the procyclic form that lives in the Tsetse vector. In contrast, EIF4E1 is dispensable during differentiation, but is required for establishment of growing procyclic forms. In Leishmania, there is some evidence that EIF4E1 might be active in translation initiation, via direct recruitment of EIF3. However in T. brucei, EIF4E1 showed no detectable association with other translation initiation factors, even in the complete absence of 4EIP. There was some evidence for interactions with NOT complex components, but if these occur they must be weak and transient. We found that EIF4E1is less abundant in the absence of 4EIP, and RNA pull-down results suggested this might occur through co-translational complex assembly. We also report that 4EIP directly recruits the cytosolic terminal uridylyl transferase TUT3 to EIF4E1/4EIP complexes. There was, however, no evidence that TUT3 is essential for 4EIP function.

Leflunomide improves psoriasis in patients with psoriatic arthritis: an in-depth analysis of data from the TOPAS study.

BACKGROUND: Leflunomide has shown promise in the treatment of psoriasis. OBJECTIVE: To provide an in-depth analysis of the effect of leflunomide on psoriasis in patients with psoriatic arthritis (PsA). METHODS: 190 patients with plaque psoriasis (at least 3% skin involvement) and active PsA were randomized to double-blind treatment with leflunomide (100 mg/day loading dose for 3 days followed by 20 mg/day orally) or placebo for 24 weeks. RESULTS: As previously reported, leflunomide resulted in a significantly higher Psoriatic Arthritis Response Criteria response rate than placebo (58.9 vs. 29.7%; p < 0.0001). Significant differences in favor of leflunomide were also observed in the Psoriasis Area and Severity Index (PASI 50 in 30.4% of patients vs. 18.9% for placebo; p = 0.05), target lesion response (46.4 vs. 25.3%; p = 0.0048), combined skin and joint response (27.2 vs. 8.9%; p < 0.0001), Dermatology Life Quality Index (improvement of 1.9 points vs. 0.2; p = 0.0173) and certain SF-36 subdomains. Dermatological responses were observed at the earliest examination (4 weeks) and increased throughout the 24-week study. CONCLUSION: Once-daily oral leflunomide is an effective and convenient treatment for PsA and plaque psoriasis.

Efficacy and safety of leflunomide in the treatment of psoriatic arthritis and psoriasis: a multinational, double-blind, randomized, placebo-controlled clinical trial.

OBJECTIVE: Current treatment options for psoriatic arthritis (PsA) are limited. Leflunomide, an oral pyrimidine synthesis inhibitor, is highly effective in the treatment of rheumatoid arthritis, and small studies have suggested similar efficacy in PsA. We undertook this double-blind, randomized, placebo-controlled trial to evaluate the efficacy and safety of leflunomide in patients with PsA and psoriasis. METHODS: One hundred ninety patients with active PsA and psoriasis (at least 3% skin involvement) were randomized to receive leflunomide (100 mg/day loading dose for 3 days followed by 20 mg/day orally) or placebo for 24 weeks. The primary efficacy end point was the proportion of patients classified as responders by the Psoriatic Arthritis Response Criteria (PsARC). Additional efficacy (joint and skin involvement), safety, and quality-of-life assessments were performed. RESULTS: At 24 weeks, 56 of 95 leflunomide-treated patients (58.9%; 95% confidence interval [95% CI] 48.4-68.9) and 27 of 91 placebo-treated patients (29.7% [95% CI 20.6-40.2]) were classified as responders by the PsARC (P < 0.0001). Significant differences in favor of leflunomide were also observed in the proportions of patients achieving modified American College of Rheumatology 20% improvement criteria, improvement in the designated psoriasis target lesion, and mean changes from baseline in Psoriasis Area and Severity Index scores and quality-of-life assessments. Diarrhea and alanine aminotransferase increases occurred at higher rates in the leflunomide group. No cases of serious liver toxicity were observed. CONCLUSION: Leflunomide is an effective treatment for PsA and psoriasis, providing a safe and convenient alternative to current therapies.