The p68 protein, an archetypical member of the DEAD box family of RNA helicases, exhibits both ATPase and RNA helicase dependent/independent activities. To date the p68 protein has been implicated in most parts of RNA metabolism including ribosome biogenesis, transcription, RNA decay, miRNA processing and pre-mRNA processing. Alterations in both expression and functional activity of p68 have been linked to carcinogenesis, with p68 exhibiting both tumour suppressive and oncogenic properties, highlighting the extremely contextual nature of p68. Recently, p68 has been shown to be required for transcriptional co-activation of the p53 tumour suppressor, permitting the recruitment of p53 to selective p53-responsive promoters. In addition, p68 was shown to be required for p21 induction through both the recruitment of p53 and RNA pol II to the p21 promoter in response to DNA damage: Specifically, p68 was shown to be essential for the p53 dependent induction of the p21 mediated G1/S cell cycle arrest under DNA damage conditions. Here I show the pre-mRNA processing function of p68 is also required to facilitate splicing of the p21 pre-RNA under basal and DNA damage conditions, an effect found to be p53-independent. Importantly, the p68 protein is not the only product of the DDX5 gene. DDX5 also gives rise to a long non-coding RNA species identified through retention of intron 11. Here I also present, through siRNA knockdown studies and analysis of the expression of the DDX5 lncRNA, p68 and p21 proteins in breast cancer tissue, that these gene products may differentially regulate p21 levels and that the DDX5 gene may exhibit multiple mechanisms to control p21 expression. In addition, through Pulse SILAC proteomics and western blot validation I have identified a number of potential targets of the DDX5 lncRNA and miRNA species encoded within intron 11.
|Date of Award||2015|
|Supervisor||Frances Fuller-Pace (Supervisor)|