Abstract
The signal recognition particle (SRP) is a ribonucleoprotein complex fundamental for co-translational delivery of proteins to their proper membrane localization and secretory pathways. Literature of the past two decades has suggested new roles for individual SRP components, 7SL RNA and proteins SRP9, SRP14, SRP19, SRP54, SRP68 and SRP72, outside the SRP cycle. These noncanonical functions interconnect SRP with a multitude of cellular and molecular pathways, including virus-host interactions, stress response, transcriptional regulation and modulation of apoptosis in autoimmune diseases. Uncovered novel properties of the SRP components present a new perspective for the mammalian SRP as a biological modulator of multiple cellular processes. As a consequence of these findings, SRP components have been correlated with a growing list of diseases, such as cancer progression, myopathies and bone marrow genetic diseases, suggesting a potential for development of SRP-target therapies of each individual component. For the first time, here we present the current knowledge on the SRP noncanonical functions and raise the need of a deeper understanding of the molecular interactions between SRP and accessory cellular components. We examine diseases associated with SRP components and discuss the development and feasibility of therapeutics targeting individual SRP noncanonical functions.
Highlights
The precise cellular localization of nascent proteins is an essential process required for maintaining homeostasis, cell organization and survival (Hartl et al, 2011)
SRP68 has been identified as a component of CASC3-containing exon junction ribonucleoprotein complexes (RNPs) complex (EJC) through a weak RNA-interaction (Mabin et al, 2018) and as a binding partner of the TRAnsport Protein Particle complex subunit 2 (TRAPPC2), a trafficking complex localized in perinuclear granular structures (Figure 4D) (Zappa et al, 2019)
The signal recognition particle (SRP) components are extensively involved in a large range of cellular processes other than its original role in protein translocation, underlying a dynamic plasticity of SRP RNPs in cells
Summary
The precise cellular localization of nascent proteins is an essential process required for maintaining homeostasis, cell organization and survival (Hartl et al, 2011). SRP components were first identified as integral part of the SRP machinery, they have been implicated in regulation of many cellular processes, including gene expression, viral infection, apoptosis and stress response (Table 1). Performing a dynamic choreography, SRP68/72 heterodimer is either involved in protein targeting associated with the SRP complex or involved in histone-binding activity, transcription regulation and potentially other chromatin-related functions.
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