Page 2 - W. RNA biology

[W. RNA biology-1]

Structural and functional analysis of cancer-associated

variants of the RNA helicase DDX3

Ryan A Flynn², Stephen N Floor³, Jennifer A Doudna³, Howard Y Chang², Yoon-Jae Cho⁴˙⁵, Sekyung Oh¹˙*

¹Department of Medical Sciences, Catholic Kwandong University, Incheon 22711, South Korea, ²Department of Dermatology,

Stanford University, Stanford, CA 94305, USA, ³Department of Molecular and Cell Biology, Universitiy of California, Berkeley,
CA 94720, USA, ⁴Department of Neurology, Stanford University, Stanford, CA 94305, USA, ⁵Department of Pediatrics, Oregon

Health and Science University, Portland, OR 97239,USA

DDX3X gene, encoding a DEAD-box family RNA helicase DDX3, is frequently mutated in many cancers. The nature

and scope of DDX3's interactions with RNA remain unclear, however. We here show DDX3 collaborates extensively
with the translation initiation machinery through direct binding to 5'UTRs of nearly all coding RNAs, specific sites
on the 18S rRNA, and multiple components of the translation initiation complex. Impairment of translation initiation

is also evident in primary medulloblastomas harboring mutations in DDX3X, further highlighting DDX3's role in this
process. Arsenite-induced stress shifts DDX3 binding from the 5'UTR into the coding region of mRNAs concomitant

with a general reduction of translation, and both the shift of DDX3 on mRNA and decreased translation are blunted
by expression of a catalytically-impaired, cancer-associated DDX3(R534H) variant. Furthermore, despite the global

repression of translation induced by arsenite, translation is preserved on select genes involved in chromatin
organization in DDX3(R534H)-expressing cells. Thus, DDX3 interacts extensively with RNA and ribosomal machinery

to help remodel the translation landscape in response to stress, while cancer-related DDX3 variants adapt this
response to selectively preserve translation.