The biology of the RNA binding protein guanine-rich sequence binding factor 1.

The mechanisms that drive the expression of a gene into its final protein product can be sub-divided into three levels: transcriptional, post-transcriptional and post-translational events. To facilitate the development and maintenance of a multi-cellular organism precise regulatory circuits are needed to ensure the survival of the organism and its ability to respond to changes in its environment. The key element of post-transcriptional regulation is RNA. Within the cell RNA exists in the form of ribonucleoproteins (RNPs), which are characterised by the underlying RNA and the proteins that are associated to it. The eukaryotic cell contains a vast plethora of RNA-binding proteins (RBPs) that control the complex fate of cellular RNAs. One of such RBPs is Guanine-rich sequence binding factor 1 (Grsf1). Grsf1 belongs to a group of heterogeneous nuclear RNPs that are characterised by the presence of an RNA binding domain designated RNA recognition motif (RRM). Grsf1 is present in most eukaryotic cells and is located in the nucleus as well as in the cytoplasm. Thus, its activity has been related to nuclear processes (RNA splicing) as well as cytoplasmic events (translation initiation). However, its full functional significance is not yet understood. Grsf1 has been implicated in the influenza viral life cycle, embryonic brain development and the regulation of apoptosis. Moreover, Grsf1 is a functional component of several cellular signalling pathways as well as of the regulation of the cellular redox homeostasis. This review summarises the present knowledge of Grsf1 biology to bring the scattered reports of Grsf1 function into a proper context.