RNA recognition motif 1 (RRM1) found in vertebrate Hu-antigen R (HuR)
This subgroup corresponds to the RRM1 of HuR, also termed ELAV-like protein 1 (ELAV-1), a ubiquitously expressed Hu family member. It has a variety of biological functions mostly related to the regulation of cellular response to DNA damage and other types of stress. HuR has an anti-apoptotic function during early cell stress response; it binds to mRNAs and enhances the expression of several anti-apoptotic proteins, such as p21waf1, p53, and prothymosin alpha. Meanwhile, HuR also has pro-apoptotic function by promoting apoptosis when cell death is unavoidable. Furthermore, HuR may be important in muscle differentiation, adipogenesis, suppression of inflammatory response and modulation of gene expression in response to chronic ethanol exposure and amino acid starvation. Like other Hu proteins, HuR contains three RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains). RRM1 and RRM2 may cooperate in binding to an AU-rich RNA element (ARE). RRM3 may help to maintain the stability of the RNA-protein complex, and might also bind to poly(A) tails or be involved in protein-protein interactions.