title: Discovery of novel interacting partners of PSMD9, a proteasomal chaperone: Role of an Atypical and versatile PDZ-domain motif interaction and identification of putative functional modules.
abstract: PSMD9 (Proteasome Macropain non-ATPase subunit 9), a proteasomal assembly chaperone, harbors an uncharacterized PDZ-like domain. Here we report the identification of five novel interacting partners of PSMD9 and provide the first glimpse at the structure of the PDZ-domain, including the molecular details of the interaction. We based our strategy on two propositions: (a) proteins with conserved C-termini may share common functions and (b) PDZ domains interact with C-terminal residues of proteins. Screening of C-terminal peptides followed by interactions using full-length recombinant proteins, we discovered hnRNPA1 (an RNA binding protein), S14 (a ribosomal protein), CSH1 (a growth hormone), E12 (a transcription factor) and IL6 receptor as novel PSMD9-interacting partners. Through multiple techniques and structural insights, we clearly demonstrate for the first time that human PDZ domain interacts with the predicted Short Linear Sequence Motif (SLIM) at the C-termini of the client proteins. These interactions are also recapitulated in mammalian cells. Together, these results are suggestive of the role of PSMD9 in transcriptional regulation, mRNA processing and editing, hormone and receptor activity and protein translation. Our proof-of-principle experiments endorse a novel and quick method for the identification of putative interacting partners of similar PDZ-domain proteins from the proteome and for discovering novel functions.
authors.affiliation: Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre (TMC), Kharghar, Navi Mumbai 410210, India.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Sangith
authors.affiliation: Bioinformatics Institute ASTAR, 30 Biopolis Street, #07-01 Matrix, Singapore 138671, Singapore ; Experimental Therapeutics Centre (A*STAR), 31 Biopolis Street, #03-01 Helios, Singapore 138669, Singapore.
authors.forename: Kannan
authors.initials: K
authors.lastname: Srinivasaraghavan
authors.affiliation: Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre (TMC), Kharghar, Navi Mumbai 410210, India.
authors.forename: Indrajit
authors.initials: I
authors.lastname: Sahu
authors.affiliation: Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre (TMC), Kharghar, Navi Mumbai 410210, India.
authors.forename: Ankita
authors.initials: A
authors.lastname: Desai
authors.affiliation: Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre (TMC), Kharghar, Navi Mumbai 410210, India.
authors.forename: Spandana
authors.initials: S
authors.lastname: Medipally
authors.affiliation: Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre (TMC), Kharghar, Navi Mumbai 410210, India.
authors.forename: Arun Kumar
authors.initials: AK
authors.lastname: Somavarappu
authors.affiliation: Bioinformatics Institute ASTAR, 30 Biopolis Street, #07-01 Matrix, Singapore 138671, Singapore ; School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore ; Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore.
authors.forename: Chandra
authors.initials: C
authors.lastname: Verma
authors.affiliation: Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre (TMC), Kharghar, Navi Mumbai 410210, India.
authors.forename: Prasanna
authors.initials: P
authors.lastname: Venkatraman
keywords: C-termini; ELISA, enzyme linked immunosorbent assay; GH, growth hormone; IL6 receptor, interleukin 6 receptor; PDZ; PSMD9; PSMD9, Proteasome Macropain non-ATPase subunit 9; Proteasome; hnRNPA1, heterogeneous nuclear ribonucleoprotein A1