INVESTIGATING THE ROLE OF DEAD-BOX HELICASE DDX3 MUTATIONS IN MEDULLOBLASTOMA

Abstract

DEAD-box proteins are a highly conserved family of proteins known to function as RNA helicases and ribonucleoprotein remodeling enzymes. These proteins are involved in cellular functions such as pre-mRNA processing, translation, and mRNA decay, which are vital for successful gene expression. DEAD-box proteins have increasingly been linked to disease, including sequencing studies that identified frequent mutations in the DEAD-box protein DDX3 in patients with medulloblastoma. This study examined the role that these mutations play in the development of medulloblastoma using the model organism Saccharomyces cerevisiae. Specific conserved medulloblastoma point mutations were introduced into DED1, the yeast ortholog of DDX3, using site-directed mutagenesis, and the resulting strains were compared to the wild type in growth assays at permissive and restrictive temperatures. Strains that showed phenotypic defects were analyzed further through the use of a variety of in vivo studies designed to investigate the efficiency of translation in the mutant cells. The data has shown that despite growth defects, the mutant cells can be devoid of general translation defects. We propose that these ded1 medulloblastoma mutations can directly affect translation initiation and repression or other cellular processes.