DIS3 is the catalytic subunit of the exosome, a protein complex involved in the 3’ to 5’ degradation of RNAs. DIS3 is a highly conserved exoribonuclease, also known as Rrp44. Global sequencing studies have identified DIS3 as being mutated in a range of cancers, with a considerable incidence in multiple myeloma. In this work, we have identified two proteincoding isoforms of DIS3. Both isoforms are functionally relevant and result from alternative splicing. They differ from each other in the size of their N-terminal PIN domain, which has been shown to have endoribonuclease activity and tether DIS3 to the exosome. Isoform 1 encodes a full-length PIN domain, whereas the PIN domain of isoform 2 is shorter and is missing a segment with conserved amino-acids. We have carried out biochemical activity assays on both isoforms of full-length DIS3 as well as the isolated PIN domains. We find that isoform 2, despite missing part of the PIN domain, has greater endonuclease activity compared to isoform 1. Examination of the available structural information allows us to provide a hypothesis to explain this altered behaviour. Our results also show that multiple myeloma patient cells and all cancer cell lines tested have higher levels of isoform 1 compared to isoform 2 whereas Acute Myeloid Leukemia (AML) and chronic myelomonocytic leukaemia (CMML) patient cells and samples from healthy donors have similar levels of isoforms 1 and 2. Together, our data indicate that significant changes in the ratios of the two isoforms could be symptomatic of haematological cancers.
Funding
Drug-induced selective lethality in populations of DNMT3A knockdown cells; G2782; WELLCOME TRUST; 218435/Z/19/Z
Mining the Wnt signalling-responsive surfaceome for drug targets in acute myeloid leukaemia; G3090; WELLCOME TRUST
How does SARS CoV-2 infect blood vessels?; G3146; UK RESEARCH AND INNOVATION; MR/V036750/1
In vitro modelling and therapeutic targeting of tumour cell migration in chronic lymphocytic leukaemia.; G2544; BLOODWISE; 18005
Structural Biology of DNA Damage Response and Repair Mechanisms; G2176; CANCER RESEARCH UK; C302/A24386
Modelling and targeting Acute Myeloid Leukaemia cells in the Bone Marrow protective niche; G3106; SUSSEX CANCER FUND FOR TREATMENT AND RESEARCH