Tumor suppressor programmed cell death protein 4 (PDCD4) inhibits the translation initiation factor eIF4A, an RNA helicase that catalyzes the unwinding of secondary structure at the 5 -untranslated region of mRNAs and controls the initiation of translation. Here, we determined the crystal structure of the human eIF4A and PDCD4 complex. The structure reveals that one molecule of PDCD4 binds to the two eIF4A molecules through the two different binding modes. While the two MA3 domains of PDCD4 bind to one eIF4A molecule, the C-terminal MA3 domain alone of the same PDCD4 also interacts with another eIF4A molecule. The eIF4A-PDCD4 complex structure suggests that the MA3 domain(s) of PDCD4 binds perpendicular to the interface of the two domains of eIF4A, preventing the domain closure of eIF4A and blocking the binding of RNA to eIF4A, both of which are required events in the function of eIF4A helicase. The structure, together with biochemical analyses, reveals insights into the inhibition mechanism of eIF4A by PDCD4 and provides a framework for designing chemicals that target eIF4A.translation inhibition ͉ tumor suppressor ͉ RNA helicase ͉ domain closure ͉ MA3 domain P rogrammed cell death protein 4 (PDCD4) is a translation inhibitor that suppresses neoplastic transformation in cultured cells and transgenic mice (1-3). Loss or reduced expression of PDCD4 has been implicated in the development and progression of a variety of aggressive human cancers (4-6). PDCD4 is regulated by the S6K1 kinase and the SCF ␤TRCP ubiquitin ligase in response to the activation of the mTOR pathway by mitogens, and the controlled degradation of PDCD4 is essential for efficient protein synthesis and consequently for cell growth and proliferation (7).PDCD4 is believed to perform its tumor suppressor function primarily through interaction with eIF4A and eIF4G, which are components of mRNA-binding complex eIF4F (8). eIF4A is a DEAD-box RNA helicase, with two domains, that unwinds the secondary structures in 5Ј-untranslated region (UTR) and cap of mRNA and thereby facilitates ribosome scanning (8). eIF4G is an adaptor protein that coordinates assembly of translation factors and the small ribosomal subunit (8). PDCD4 is believed to inhibit cap-dependent translation by directly inhibiting the helicase activity of eIF4A or by competing with eIF4G for binding to eIF4A and preventing assembly into a eukaryotic initiation complex, eIF4F, or both (1, 9, 10).PDCD4 is formed with the two MA3 domains at its middle (mMA3) and C-terminal regions (cMA3) (9, 11-13). Mutational and NMR binding analysis have shown that PDCD4 uses both MA3 domains to interact with eIF4A and prevents translation (9, 10). However, other studies have demonstrated that the cMA3 domain alone is sufficient for the inhibition of RNA helicase and translation (12). The interactions between eIF4A and PDCD4 have been analyzed in several mutational and NMR mapping studies (1, 9, 10). Nevertheless, it is unclear from these studies how PDCD4 inhibits eIF4A at the molecular level. To elucidate ...

A p.V37I variant of GJB2 has been reported from subjects with moderate or slight hearing loss especially in East Asian populations. This study aimed to estimate the prevalence of the p.V37I variant among such subjects and prove, epidemiologically, its pathogenic potential to cause mild hearing loss. A total of 380 subjects from 201 families with hearing loss were enrolled. From them, 103 families were selected who had autosomal recessive inheritance or sporadic occurrence of hearing loss and who were younger than 15 years old. GJB2 sequencing was carried out for the probands of all 103 families. The prevalence of the p.V37I variant was compared between the subtle, mild or moderate hearing loss (group I) and the severe or profound hearing loss (group II) groups. Where possible, a targeted next generation sequencing of 82 deafness genes was performed from the p.V37I carrier to exclude the existence of other pathogenic genes. Five (4.8%) of 103 probands were found to carry p.V37I. The carrier frequency of p.V37I among group I (18.2%) was significantly higher than that of group II (1.2%) or the reported Korean normal hearing control group (1.0%). Detection of the p.V37I variant of GJB2 in 18.2% of Koreans with mild hearing loss strongly suggests its contribution to the pathogenesis of milder hearing loss, which might justify sequencing of GJB2 from these subjects in the Korean population.

Characterizing the molecular immune subtype and micro-environment of lung cancer is necessary to understand immunogenic interactions between infiltrating immune and stromal cells, and how tumor cells overcome immune checkpoint blockades. This study seeks to identify computational methodologies for subtyping gene expression-based tumor-immune micro-environment interactions, which differentiate non-small cell lung cancer (NSCLC) into immune-defective and immune-competent subtypes. Here, 101 lung squamous cell carcinomas (LUSCs) and 87 lung adenocarcinomas (LUADs) tumor samples have been analyzed. Several micro-environmental factors differentially induce LUAD or LUSC immune subtypes, as well as immune checkpoint expression. In particular, tumor-associated macrophages (TAMs) are key immune cells play a vital role in inflammation and cancer micro-environments of LUSCs; whereas, regulatory B cells are immunosuppressive and tumorigenic in LUADs. Additionally, cytolytic activity upon CD8+ T cell activation is decreased by the abundance of B cells and macrophages in immune-competent subtypes. Therefore, identifying immune subtypes in lung cancer and their impact on tumor micro-environment will lead to clinical tools for assessing LUADs and LUSCs in patients, as well as maximize the efficacy of immune checkpoint inhibitors.