HuR differentially regulates unique subsets of mRNAs in estrogen receptor negative and positive breast cancer. Homo sapiens

Analysis of RNA immunoprecipitation of HuR, a RNA binding protein (RBP), in breast cancer cell lines. This approach, utilizing RNA immunoprecipitation hybridized to microarray (RIP-Chip), provides global identification of putative endogenous mRNA targets of different RBPs. HuR is an RBP that binds to the AU-rich (ARE) regions of labile mRNAs, such as proto-oncogenes, facilitating their translation into protein. HuR has been shown to play a role in cancer progression and elevated levels of cytoplasmic HuR directly correlate with increased invasiveness and poor prognosis for many cancers, including those of the breast. We used HuR RIP-Chip as a comprehensive and systematic method to survey breast cancer target genes in both MCF-7 (estrogen receptor positive, ER+) and MDA-MB-231 (estrogen receptor negative, ER-) breast cancer cell lines. We identified unique subsets of HuR associated mRNAs found individually or in both cell types. Two novel HuR targets, CD-9 and CALM-2, were identified and validated by quantitative RT-PCR and biotin pulldown analysis. Our findings reveal that the differential regulation of these two cancer-related genes by HuR was contingent upon the cellular environment. Overall design: RNA immunoprecipitation of the HuR RNA binding protein by 3A2 antibody and IgG (control) from two human breast cancer cell lines, MCF-7 and MDA-MB-231 .