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The tumour suppressor CDC73 is a key regulator of RNA polymerase II transcribed microRNA (280)

Kristie-Ann Dickson 1 , Abdullah Qashgry 1 , Tharani Sabaretnam 1 , Shih-Ping Su 1 , Jaynish Shah 1 , Deborah J Marsh 1
  1. Hormones and Cancer, Functional Genomics Laboratory, Kolling Institute of Medical Research, St Leonards, NSW, Australia

Background: Loss or down-regulation of the tumour suppressor protein Cell Division Cycle 73 (CDC73) has been implicated in various cancers, these include parathyroid, renal, uterine, colorectal, lung and breast cancer. CDC73 is a component of the RNA polymerase II associated factor 1 complex (PAF-1c), which interacts with RNA polymerase II to direct transcription of messenger RNA (mRNA) and microRNA (miRNA).

Aim: To identify miRNAs likely to be involved in CDC73-mediated tumorigenesis.

Methods: Western Blot and qRT-PCR methods were used to confirm down-regulation of the CDC73 protein by small interfering RNA (siRNA) in the endometrial cancer cell line HEC-1-B, 48 and 72 h post transfection. Expression of 377 unique miRNA and a panel of controls were profiled using TaqMan low-density arrays (TLDAs) in CDC73 down-regulated cells, or cells treated with a non-silencing siRNA. TLDA data was analysed using Data Assist software (Life Technologies) and the miRNA targets predicted by interrogating multiple miRNA target databases using R and Bioconductor packages.

Results: CDC73 protein and mRNA levels were reduced by 70% and 80% respectively at 48 and 72 h post transfection with CDC73 siRNA compared to non-silencing controls. TLDA analyses yielded data for 182 miRNAs, the majority of which were down-regulated in cells treated with a CDC73 siRNA compared to treatment with non-silencing siRNA at both 48 and 72 h post transfection.

Conclusions: The expression profiles of most miRNA were reduced with down-regulation of wild-type CDC73, suggesting that the identified miRNA are driven by CDC73-associated with RNA polymerase II transcriptional events. Future studies will elucidate the function and regulation of identified miRNA as well as their target genes relative to CDC73 activity, which may provide the basis for identifying novel therapeutic and diagnostic strategies for cancer.