Atypical ubiquitin ligase RNF31: the nuclear factor modulator in breast cancer progression

Breast cancer causes the No. 1 women cancer prevalence and the No. 2 women cancer mortality worldwide. Nuclear receptor/transcriptional factor signaling is aberrant and plays important roles in breast cancer pathogenesis and evolution, such as estrogen receptor alpha (ER alpha/ESR1), tumor protein p53 (p53/TP53) and Nuclear factor kappa B (NF kappa B). About 60-70 % of breast tumors are ER alpha positive, while approximate 70 % of breast tumors are P53 wild type. Recent studies indicate that nuclear receptors/transcriptional factors could be tightly controlled through protein post-translational modification. The nuclear receptors/transcriptional factors could endure several types of modifications, including phosphorylation, acetylation and ubiquitination. Compared with the other two types of modifications, ubiquitination was mostly linked to protein degradation process, while few researches focused on the functional changes of the target proteins. Until recent years, ubiquitination process is no longer regarded as merely a protein degradation process, but aslo treated as one kind of modification signal. As an atypical E3 ubiquitin ligase, RNF31 was previously found to facilitate NF kappa B signaling transduction through linear ubiquitination on IKK gamma (I kappa B kinase gamma). Our previous studies showed important regulatory functions of RNF31 in controlling important oncogenic pathways in breast cancer, such as ER alpha and p53. This review highlights recent discoveries on RNF31 functions in nuclear factor modifications, breast cancer progression and possible therapeutic inhibitors targeting RNF31.