Cross Talk between Cellular Regulatory Networks Mediated by Shared Proteins

Abstract

Moonlighting proteins mediate cross talk between different pathways and cellular control networks. Sometimes, they even coordinate subsequent steps in the same pathway. For this Outlook paper we asked the question, which cellular processes employ multifunctional proteins (MFPs) and what makes them so attractive to cells and organisms. After reviewing their widespread occurrence, we will focus on higher eukaryotic model systems and on few examples that are linked to ongoing work in our laboratory. We will discuss the activities of transcription factor IIH (TFIIH), and its subcomplexes containing Xpd and Cdk7, and we will cover an aminoacyl-tRNA synthetase (LysRS) and DEAD box RNA helicases. Furthermore, we will analyze how cells are able to properly regulate the different biological activities of multifunctional proteins and which advantages such proteins offer to cells and organisms. Finally we also note that the proteins we discuss are linked to tumor formation or recruited by viruses that coopt the multifunctional protein for yet another purpose.