RNA-Binding Protein ZFP36L1 Suppresses Hypoxia and Cell-Cycle Signaling

ZFP36L1 is a tandem zinc-finger RNA-binding protein that recognizes conserved adenylate-uridylate-rich elements (ARE) located in 3'untranslated regions (UTR) to mediate mRNA decay. We hypothesized that ZFP36L1 is a negative regulator of a posttranscriptional hub involved in mRNA half-life regulation of cancer-related transcripts. Analysis of in silico data revealed that ZFP36L1 was significantly mutated, epigenetically silenced, and downregulated in a variety of cancers. Forced expression of ZFP36L1 in cancer cells markedly reduced cell proliferation in vitro and in vivo, whereas silencing of ZFP36L1 enhanced tumor cell growth. To identify direct downstream targets of ZFP36L1, systematic screening using RNA pull-down of wild-type and mutant ZFP36L1 as well as whole transcriptome sequencing of bladder cancer cells {plus minus} tet-on ZFP36L1 was performed. A network of 1,410 genes was identified as potential direct targets of ZFP36L1. These targets included a number of key oncogenic transcripts such as HIF1A, CCND1, and E2F1. ZFP36L1 specifically bound to the 3'UTRs of these targets for mRNA degradation, thus suppressing their expression. Dual luciferase reporter assays and RNA electrophoretic mobility shift assays showed that wild-type, but not zinc-finger mutant ZFP36L1, bound to HIF1A 3'UTR and mediated HIF1A mRNA degradation, leading to reduced expression of HIF1A and its downstream targets. Collectively, our findings reveal an indispensable role of ZFP36L1 as a posttranscriptional safeguard against aberrant hypoxic signaling and abnormal cell-cycle progression. SIGNIFICANCE: RNA-binding protein ZFP36L1 functions as a tumor suppressor by regulating the mRNA stability of a number of mRNAs involved in hypoxia and cell-cycle signaling.

Penetrating foreign body in the masticator space with injury to the internal maxillary artery: a surgical challenge

INTRODUCTION Foreign bodies (FBs) in the masticator space (MS) are a unique problem because of the difficulty of accessing this deep compartment within the head and neck. In addition, MS contents include critical structures such as the internal maxillary artery (IMA) and mandibular nerve. CASE HISTORY A 39-year-old tradesman was involved in a construction accident whereby a metallic projectile from a machinery drill penetrated his left cheek. Computed tomography revealed a metallic object of dimension 1.9 ×1.2 cm within the MS, with concomitant fracture of left maxillary anterior and lateral walls. Surgery was indicated in view of constant pain and swelling. The FB was removed through the cheek laceration with the aid of an X-ray image intensifier. Persistent significant bleeding was observed within the wound cavity after FB removal that could not be arrested despite attempts at haemostasis with adrenaline packing and oxidised cellulose polymers. Urgent selective left external carotid angiography showed breach of a distal branch of the left internal maxillary artery with contrast extravasation. Embolisation of this branch was undertaken successfully with a liquid agent. CONCLUSIONS This is the first time a FB within the MS with injury to the internal maxillary artery has been described.

Molecular cloning of a cardiotoxin structural gene from Malayan spitting cobra (Naja naja sputatrix)

The structural gene and cDNA encoding cardiotoxin in Naja naja sputatrix have been cloned and characterized with a view to study the gene protein relationships and also to produce pure protein in large amounts. Using the polymerase chain reaction on the total RNA isolated from the venom glands, the structural gene (180 bp) has been synthesized and expressed in Escherichia coli to produce a fusion protein with beta-galactosidase. Immunoblotting using polyclonal antibodies raised against the total venom in rabbits demonstrated the presence of cross-reacting proteins in plaques produced by recombinant lambda gt11 phages.