Oxygen-regulated expression of the RNA-binding proteins RBM3 and CIRP by a HIF-1-independent mechanism

Abstract

The transcriptional regulation of several dozen genes in response to low oxygen tension is mediated by hypoxia-inducible factor 1 (HIF-1), a heterodimeric protein composed of two subunits, HIF-1α and HIF-1β. In the HIF-1α-deficient human leukemic cell line, Z-33, exposed to mild (8% O2) or severe (1% O2) hypoxia, we found significant upregulation of two related heterogenous nuclear ribonucleoproteins, RNA-binding motif protein 3 (RBM3) and cold inducible RNA-binding protein (CIRP), which are highly conserved cold stress proteins with RNA-binding properties. Hypoxia also induced upregulation of RBM3 and CIRP in the murine HIF-1β-deficient cell line, Hepa-1 c4. In various HIF-1 competent cells, RBM3 and CIRP were induced by moderate hypothermia (32°C) but hypothermia was ineffective in increasing HIF-1α or vascular endothelial growth factor (VEGF), a known HIF-1 target. In contrast, iron chelators induced VEGF but not RBM3 or CIRP. The RBM3 and CIRP mRNA increase after hypoxia was inhibited by actinomycin-D, and in vitro nuclear run-on assays demonstrated specific increases in RBM3 and CIRP mRNA after hypoxia, which suggests that regulation takes place at the level of gene transcription. Hypoxia-induced RBM3 or CIRP transcription was inhibited by the respiratory chain inhibitors NaN3 and cyanide in a dose-dependent fashion. However, cells depleted of mitochondria were still able to upregulate RBM3 and CIRP in response to hypoxia. Thus, RBM3 and CIRP are adaptatively expressed in response to hypoxia by a mechanism that involves neither HIF-1 nor mitochondria.

Proliferation control strategies to improve productivity and survival during CHO based production culture

“…Decreased levels of microRNAs were also reported in mouse N2a neuroblastoma cells expressing an RBM3-c-Myc fusion protein, indicating that RBM3 can interact with the miRNA fraction and hence regulate global levels of protein synthesis (Dresios et al 2005). RBM3 like CIRP can be regulated by changes in oxygen levels which further indicates a link between the low-temperature and oxygen-response pathways (Wellmann et al 2004).…”

The RNA-binding protein RBM3 is involved in hypothermia induced neuroprotection

“…For quantitation, cDNA was amplified by use of SYBR GreenER qPCR SuperMix Universal (Invitrogen) and real-time PCR was carried out an a Rotor-Gene 6000 (Corbett Life Science, Sydney, Australia) as previously described (Wellmann et al, 2008). Primers for detection of the following mouse mRNA molecules have been published previously, RBM3 and reference gene RPL13A (Wellmann et al, 2004), DCX and p35 (Ge et al, 2006). For detection of rat RBM3 mRNA the mouse RBM3 primers could be used due to 100% homology and the primers for the rat reference gene RPL13A have been published previously (Wellmann et al, 2008).…”

Cloning and expression of cold-inducible RNA binding protein in domestic yak (Bos grunniens)

“…Then previous investigations showed that the level of CIRP mRNA in mice testis was the highest than other various tissues [16], but our data showed CIRP level in yak hearts was the highest. Wellmann et al [13] showed hypoxic transduction pathways shared common components with cold-stress transduction pathways, and expression of CIRP was stimulated under hypoxic conditions by a hypoxia inducible transcription factor (HIF)-1 independent mechanism. Moreover, we propose the highest levels of CIRP in yak heart might be able to make yaks respond and adapt quickly to hypoxia through a myriad of mechanisms.…”