Abstract

Background

The microenvironment of solid tumours is characterised by regions of low oxygen (hypoxia), which results from the abnormal tumour vasculature and high oxygen demand. Tumour hypoxia plays a pivotal role in tumour progression, and has been associated with increased tumour aggressiveness, metastasis, resistance to radiation therapy, and poor patient prognosis. The levels of hypoxia associated with radiation resistance, radiobiological hypoxia, also lead to a global repression in transcription rates and a replication stress-mediated DNA damage response. Three-stranded nucleic acid structures known as R loops have been described in conditions of replication stress and in aberrant transcription. Here, we investigated the presence and resolution of R loops in hypoxia.

Method

In vitro experiments were performed using the RKO colorectal cancer cell line with hypoxic treatments in the Bactron II anaerobic chamber (Shell labs) or H35 Hypoxystation (Don Whitley Scientific).

Results

A number of R loop associated genes, including RNase H and Pif1, were significantly repressed in hypoxic conditions. However, interestingly, the putative RNA:DNA helicase Senataxin, which was shown to be mutated in the neurodegenerative disorder ataxia with oculomotor apraxia 2 (AOA-2) and amyotrophic lateral sclerosis type 4 (ALS4), was upregulated specifically in radiobiological hypoxia. Senataxin has been associated with transcription, and has also been implicated in coordinating transcription with replication.

Conclusion

We are investigating whether Senataxin plays a role in the transcriptional response and replication stress observed in hypoxia.