The RNA-Binding Protein HuR Promotes Cell Migration and Cell Invasion by Stabilizing the β-actin mRNA in a U-Rich-Element-Dependent Manner

Abstract

A high expression level of the ␤-actin protein is required for important biological mechanisms, such as maintaining cell shape, growth, and motility. Although the elevated cellular level of the ␤-actin protein is directly linked to the long half-life of its mRNA, the molecular mechanisms responsible for this effect are unknown. Here we show that the RNA-binding protein HuR stabilizes the ␤-actin mRNA by associating with a uridine-rich element within its 3 untranslated region. Using RNA interference to knock down the expression of HuR in HeLa cells, we demonstrate that HuR plays an important role in the stabilization but not in the nuclear/cytoplasmic distribution of the ␤-actin mRNA. HuR depletion in HeLa cells alters key ␤-actin-based cytoskeleton functions, such as cell adhesion, migration, and invasion, and these defects correlate with a loss of the actin stress fiber network. Together our data establish that the posttranscriptional event involving HuR-mediated ␤-actin mRNA stabilization could be a part of the regulatory mechanisms responsible for maintaining cell integrity, which is a prerequisite for avoiding transformation and tumor formation.

Apoptotic-induced cleavage shifts HuR from being a promoter of survival to an activator of caspase-mediated apoptosis

“…Transfecting these plasmids into caspase-9 À / À MEFs showed that mutating the AREs caused 480% decrease in the expression of caspase-9 mRNA (Figures 3b and c). Using these cells in an actinomycin D (ActD) pulse-chase experiment, 32 we observed that mutated caspase-9 mRNA had a reduced half-life (of B4.1 h) compared with full-length caspase-9 mRNA (B6.6 h; Figures 3d and e and Supplementary Figure 4). Although AREs are generally known to destabilize their host messages, our data clearly suggest that in the case of caspase-9 mRNA, they are in fact required for its stabilization.…”

Interleukin 1β Regulation of the System xc− Substrate-specific Subunit, xCT, in Primary Mouse Astrocytes Involves the RNA-binding Protein HuR

“…Amplimers for ␤ actin were 5Ј-GTGGGCCGCTCTAGGCACCAA-3Ј (forward) and 5Ј-TCTTTGATGTCACGCACGATTTC-3Ј (reverse). COX-2 and ␤-actin mRNAs were assessed as positive controls for HuR immunoprecipitation in vehicle and IL-1␤-treated cells because both are targets of HuR (49,50). PCR products, separated in either a 1% (␤-actin) or 2% agarose (xCT and COX-2) gel containing ethidium bromide (200 g/ml), were visualized with the LI-COR Odyssey Fc infrared imaging system.…”

“…3B). Immunoprecipitation of HuR protein also pulled down COX-2 and ␤-actin mRNAs, both of which are known targets of HuR (49,50).…”

Participation of Xenopus Elr-type Proteins in Vegetal mRNA Localization during Oogenesis

“…Hu/ELAV proteins are known to specifically target localized RNAs in other systems, although no indications for a direct function of Hu/ELAV proteins in RNA localization have been described to date. In particular, HuR was reported to bind to the 3Ј-UTR of ␤-actin mRNA, which localizes to the leading edge of migrating cells, a process that also involves the Vg1RBP homolog ZBP1 (76,77). It was demonstrated that depletion of HuR results in a reduced migratory capacity of such cells, perhaps as a consequence of reduced ␤-actin mRNA stability (76).…”

“…In particular, HuR was reported to bind to the 3Ј-UTR of ␤-actin mRNA, which localizes to the leading edge of migrating cells, a process that also involves the Vg1RBP homolog ZBP1 (76,77). It was demonstrated that depletion of HuR results in a reduced migratory capacity of such cells, perhaps as a consequence of reduced ␤-actin mRNA stability (76). In neurons, the Vg1RBP homolog IMP1, together with HuD, is found to exert a repressing effect on the translation of Tau mRNA 3Ј-UTR reporters (78).…”