The variable N-terminal region of DDX5 contains structural elements and auto-inhibits its interaction with NS5B of hepatitis C virus
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Date
2012
Journal Title
Journal ISSN
Volume Title
Publisher
Portland Press
Abstract
RNA helicases of the DEAD (Asp-Glu-Ala-Asp)-box family of
proteins are involved in many aspects of RNA metabolism from
transcription to RNA decay, but most of them have also been
shown to be multifunctional. The DEAD-box helicase DDX5 of
host cells has been shown to interact with the RNA-dependent
RNA polymerase (NS5B) of HCV (hepatitis C virus). In the
present study, we report the presence of two independent NS5Bbinding
sites in DDX5, one located at the N-terminus and another
at the C-terminus. The N-terminal fragment of DDX5, which
consists of the first 305 amino acids and shall be referred as
DDX5-N, was expressed and crystallized. The crystal structure
shows that domain 1 (residues 79–303) of DDX5 contains
the typical features found in the structures of other DEADbox
helicases. DDX5-N also contains the highly variable NTR
(N-terminal region) of unknown function and the crystal structure
reveals structural elements in part of the NTR, namely residues
52–78. This region forms an extensive loop and an α-helix. From
co-immunoprecipitation experiments, the NTR of DDX5-N was
observed to auto-inhibit its interaction with NS5B. Interestingly,
the α-helix in NTR is essential for this auto-inhibition and
seems to mediate the interaction between the highly flexible
1–51 residues in NTR and the NS5B-binding site in DDX5-N.
Furthermore, NMR investigations reveal that there is a direct
interaction between DDX5 and NS5B in vitro.
Description
Keywords
Auto-inhibition, DDX5, DEAD-box family, Hepatitis C virus, NS5B, N-terminal region
Citation
Dutta, S. (2012). The variable N-terminal region of DDX5 contains structural elements and auto-inhibits its interaction with NS5B of hepatitis C virus. Biochemical Journal, 446: 37–46