Novel mechanisms controlling the cellular stress response

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A protective stress response (SR) is generated in all cells following exposure to physiological stressors such as elevated temperatures, ischaemia, osmotic shock and many other stressors. The response is characterized by the suppression of normal cellular transcription and translation and the synthesis of heat shock proteins (HSPs) that protect cells from damage largely by preventing the abnormal folding and aggregation of proteins and by mediating anti-apoptotic effects. The SR in mammals is under the control of heat shock transcription factors (HSFs) and following a stress they mediate: (i) the transcription of protective heat shock protein; (ii) drive the expression of the long non-coding RNAs Sat III encoded on non-mapped peri-centromeric regions of human chromosomes. Under stress conditions Sat III transcripts of varying length are transcribed and form scaffolds for specific transcription factors and RNA binding proteins and these sites of accumulation are termed nuclear stress bodies (nSBs) and are involved in mediating the cessation of transcription and control of splicing. The stress response of non-dividing neurones has been reported to be cell-type specific and the kinetics and level of expression of HSPs vary according to the type of stress. Importantly, altered HSF1 function is associated with ageing, cancer and many neurodegenerative diseases and suggests an altered HSR may contribute to disease aetiology. We have found previously undocumented important roles for the scaffold attachment factor B (SAFB) family of RBPs in coordinating the stress response in neuronal and non-neuronal populations of cells. SAFB1 and SAFB2 are ubiquitously expressed and found at very highly levels in the human brain. We have previously shown they coordinate the expression of coding and non-coding genes and that they are involved in alternative spicing. We have further novel findings showing that SAFB1 regulates the transcription/ stability of Sat III RNA and its paralogue SAFB2 translocated to Sat III/nSBs with the same kinetics as HSF1. In addition, both SAFB1 and SAFB2 are arginine methylated in domains known to mediate both protein-RNA and protein-protein interactions. RNA binding proteins (such as SAFB1/2) involved in regulating the stress response and found in stress bodies have also been shown to implicated in the ageing process and in the aetiology of human neurodegenerative disease.We propose that SAFB1 and SAFB2 are key components governing the cellular response to stress, and that their functions in protein complexes may be regulated by post-translational arginine methylation. Specifically, we hypothesise they are required for Sat III transcription and the recruitment of RBPs to nSBs which in turn Sat govern the cellular stress response. The specific research objectives are: 1. Identify the roles SAFB1 and SAFB2 play in regulating Sat III transcription and nSB formation. 2. Define the role arginine methylation plays in governing the functions of SAFB1 and SAFB2. 3. Identify novel SAFB1 and SAFB2 interaction partners that function under stress and non-stress conditions. 4. Characterise the role SAFB proteins play in regulating Sat III lncRNA transcription and the formation of nSBs in human neurones.The outcome of this study will be to elucidate the mechanisms by which SAFB (and other RNA binding proteins) regulate Sat III transcription and nSB formation and thereby the cellular stress response. Hence novel insights will made into the processes that underpin the neuronal and non-neuronal cell response to environmental stress, govern ageing, cancer and underpin a number of human neurodegenerative disease conditions.