A Role for Mixed Lineage Kinases in Regulating Transcription Factor CCAAT/Enhancer-binding Protein-β-dependent Gene Expression in Response to Interferon-γ

Sanjit K Roy,Peter F Johnson,Sekhar P.M Reddy,Leonidas C Platanias,Jon D Shuman,Paul S Shapiro,Dhananjaya V Kalvakolanu

doi:10.1074/jbc.m413661200

Abstract

Transcription factor CCAAT/enhancer-binding protein-beta (C/EBP-beta) regulates a variety of cellular functions in response to exogenous stimuli. We have reported earlier that C/EBP-beta induces gene transcription through a novel interferon (IFN)-response element called gamma-IFN-activated transcriptional element. We show here that IFN-gamma-induced, C/EBP-beta/gamma-IFN-activated transcriptional element-dependent gene expression is regulated by mixed lineage kinases (MLKs), members of the mitogen-activated protein kinase kinase kinase family. MLK3 appears to activate C/EBP-beta in response to IFN-gamma by a mechanism involving decreased phosphorylation of a specific phosphoacceptor residue, Ser(64), within the transactivation domain. Decreased phosphorylation of Ser(64) was independent of IFN-gamma-stimulated ERK1/2 activation and did not require the ERK phosphorylation site Thr(189) located in regulatory domain 2 of C/EBP-beta. Together these studies provide the first evidence that MLK3 is involved in IFN-gamma signaling and identify a novel mechanism of transcriptional activation by IFN-gamma.

Highlights

Transcription factor CCAAT/enhancer-binding protein-␤ (C/EBP-␤) regulates a variety of cellular functions in response to exogenous stimuli
We show here that IFN-␥-induced, C/EBP-␤/␥-IFN-activated transcriptional element-dependent gene expression is regulated by mixed lineage kinases (MLKs), members of the mitogenactivated protein kinase kinase kinase family
CEP did not significantly inhibit epidermal growth factorinduced expression through an activator protein 1-responsive element (Fig. 1D). Together these results suggest that MLK activity is critical for IFN-␥-dependent induction of IRF9

Summary

Introduction

Transcription factor CCAAT/enhancer-binding protein-␤ (C/EBP-␤) regulates a variety of cellular functions in response to exogenous stimuli. We show here that IFN-␥-induced, C/EBP-␤/␥-IFN-activated transcriptional element-dependent gene expression is regulated by mixed lineage kinases (MLKs), members of the mitogenactivated protein kinase kinase kinase family. Decreased phosphorylation of Ser was independent of IFN-␥-stimulated ERK1/2 activation and did not require the ERK phosphorylation site Thr189 located in regulatory domain 2 of C/EBP-␤ Together these studies provide the first evidence that MLK3 is involved in IFN-␥ signaling and identify a novel mechanism of transcriptional activation by IFN-␥. Our recent studies have shown that mitogen-activated protein kinases (MAPKs) play a critical role in regulating C/EBP-␤- and GATE-dependent gene expression. This occurs at least in part by phosphorylation of C/EBP␤ on Thr189 by ERK1/2 (20, 21). Our studies identified a novel IFN-␥ effector pathway involving MLKs and C/EBP␤

Methods

Results

Conclusion