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Updated: Aug 19, 2026

Studying RNA Interactors of Protein Kinase RNA-Activated during the Mammalian Cell Cycle
Published on: March 5, 2019
The human stress-activated protein kinase-interacting 1 gene encodes JNK-binding proteins
Wayne Schroder1, Gillian Bushell, Tom Sculley
1The Queensland Institute of Medical Research, 300 Herston Road, Brisbane 4029, Australia. wayneS@qimr.edu.au
Abstract:
The orthologous proteins of the stress-activated protein kinase-interacting 1 (Sin1) family have been implicated in several different signal transduction pathways. In this study, we have investigated the function of the full-length human Sin1 protein and a C-terminally truncated isoform, Sin1alpha, which is produced by alternative splicing. Immunoblot analysis using an anti-Sin1 polyclonal antibody showed that full-length Sin1 and several smaller isoforms are widely expressed. Sin1 was demonstrated to bind to c-Jun N-terminal kinase (JNK) in vitro and in vivo, while no interaction with p38- or ERK1/2-family MAPKs was observed. The Sin1alpha isoform could also form a complex with JNK in vivo. Despite localizing in distinct compartments within the cell, both Sin1 and Sin1alpha co-localized with JNK, suggesting that the Sin1 proteins could recruit JNK. Over-expression of full-length Sin1 inhibited the activation of JNK by UV-C in DG75 cells, as well as basal JNK-activity in HEK293 cells. These data suggest that the human Sin1 proteins may act as scaffold molecules in the regulation of signaling by JNK.
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