Natural antisense transcripts of HIF-1alpha are conserved in rodents.

A natural antisense transcript (aHIF), which sequence is strictly complementary to the 3' untranslated region (3'UTR) of HIF-1alpha mRNA, has been identified in human and shown to be overexpressed in renal carcinomas. We searched for aHIF in different rodent tissues. Two candidate expressed sequence tag (EST) were identified in silico and their PCR products (1.1 and 1.0 kb) were cloned and sequenced in mouse and rat, respectively. These transcripts were rigorously complementary to the 3'UTR of rodent HIF-1alpha mRNA and were broadly expressed in all mouse and rat tissues we tested. The conservation of aHIF in rodents underlined its potential importance in cell regulations. Therefore the responses of aHIF and HIF-1alpha transcripts were investigated in various types of hypoxic conditions. In freshly isolated rat renal tubules, aHIF RNA level was increased by acute hypoxia and low in normal supply of oxygen. In a rat strain raised in chronic hypobaric altitude hypoxia, aHIF transcript was greatly induced in the oxidative-type soleus and heart muscles of 3 month-old animals. By contrast, in the glycolytic-type extensor digitorum longus muscle aHIF transcript amount was lowered by hypoxia whereas HIF-1alpha transcript was highly expressed. In brain, where oxidative glycolysis takes place, HIF-1alpha mRNA and its antisense transcript levels were high and not significantly changed by altitude. Tumour cell lines cultured for 6 h in conditions mimicking hypoxia expressed lower amounts of HIF-1alpha mRNA. In two rat cell lines, aHIF transcript levels were greatly augmented after a 6-h incubation in these conditions, whereas in a mouse cell line, aHIF level was significantly reduced.

Rossignol F ，de Laplanche E ，Mounier R ，Bonnefont J ，Cayre A ，Godinot C ，Simonnet H ，Clottes E ... -  《GENE》

Natural antisense transcripts of hypoxia-inducible factor 1alpha are detected in different normal and tumour human tissues.

Hypoxia-inducible factor 1 is a heterodimeric transcription factor, made up of two subunits called HIF-1alpha and aryl receptor nuclear translocator, that regulates the expression of genes associated with adaptation to reduced oxygen pressure. The HIF-1alpha messenger RNA (mRNA) and protein are both up-regulated in common human cancers where this transcription factor is known to be involved in tumour progression. In renal carcinoma, a natural antisense of HIF-1alpha transcript (aHIF) that is complementary to the 3'untranslated region of HIF-1alpha mRNA has been described. Here, we provide a grown work for further characterisation of this natural antisense and we show that: (1) aHIF is widely expressed in normal foetal and adult human tissues as in tumour tissues. Foetal aHIF expression level is higher than adult one and high enough to affect the HIF-1alpha mRNA/aHIF transcripts ratio; (2) aHIF could expose AU rich elements present in the 3' untranslated region of HIF-1alpha mRNA and thus possibly increase the degradation speed of HIF-1alpha mRNA; and (3) aHIF promoter possesses several putative hypoxia response elements which could explain the overexpression of aHIF under hypoxic conditions, creating a negative loop of regulation of HIF-1alpha expression.

Rossignol F ，Vaché C ，Clottes E 《GENE》

aHIF but not HIF-1alpha transcript is a poor prognostic marker in human breast cancer.

Hypoxia-inducible factor-1alpha (HIF-1alpha) is part of a transcriptional factor that regulates genes involved in metabolic and vascular adaptation of tumours to oxygen restriction. A splicing variant lacking exon 14 (sHIF-1alpha) encodes a truncated protein that competes with the normal HIF-1alpha protein, decreasing its activity. A natural antisense transcript (aHIF) complementary to the 3'-untranslated region of HIF-1alpha mRNA was described recently. With a semiquantitative multiplex reverse transcriptase-PCR (RT-PCR) assay, we assessed transcript concentrations of HIF-1alpha, sHIF-1alpha and aHIF in 110 patients with invasive breast carcinoma. We found a strong positive association between HIF-1alpha and sHIF-1alpha, sHIF-1alpha and aHIF, and an inverse correlation between HIF-1alpha /sHIF-1alpha and aHIF. aHIF transcript expression was associated with poor disease-free survival in univariate (P = 0.0038) and multivariate (P = 0.0016) analyses in this series of high-risk primary breast carcinomas. In our series of breast cancer patients, aHIF, and not HIF-1alpha transcript, is a marker of poor prognosis.

Cayre A ，Rossignol F ，Clottes E ，Penault-Llorca F ... -  《-》

cDNA cloning, gene organization and variant specific expression of HIF-1 alpha in high altitude yak (Bos grunniens).

Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric basic-helix-loop-helix-PER-ARNT-SIM (bHLH-PAS) transcription factor consisting of HIF-1alpha and HIF-1beta subunits. HIF-1alpha is the oxygen-regulated subunit of HIF-1, which regulates the transcription of genes involved in oxygen homeostasis in response to hypoxia. Yak (Bos grunniens), a mammal native to high altitude (HA) region ( approximately 3500-5500 m), has successfully adapted over many generations to the chronic hypoxia of HA. In the present work, cDNA encoding HIF-1alpha has been cloned from the blood of yak. Tissue specific expression of the mRNA was analyzed in blood, heart, lung, liver and kidney by RT-PCR with primers from three different regions of cDNA. The HIF-1alpha expression was liver and blood specific. The HIF-1alpha mRNA contains 823 bp long 3'UTR that is AU-rich and contains ten AUUUA pentamers and two overlapping copies of the nonamer UUAUUUAUUUAUU. Three potential microRNAs, hsa-miR-107/mmu-miR-107/rno-miR-107, hsa-miR-18b and hsa-miR-135a/mmu-miR-135a/rno-miR-135a, targeting 3'UTR of yak HIF-1alpha, were identified by using target prediction software. The CDS encodes for 823 residues of amino acids and showed 99%, 95%, 92%, 90% and 90% similarity to domestic cattle, human, plateau pika, mouse and rat HIF-1alpha, respectively. HIF-1alpha cDNA, cloned and sequenced in the present work has revealed the evolutionary conservation through multiple sequence alignment. Liver and blood specific stability of HIF-1alpha mRNA appears miR-107 regulated.

Dolt KS ，Mishra MK ，Karar J ，Baig MA ，Ahmed Z ，Pasha MA ... -  《GENE》

APeg3, a novel paternally expressed gene 3 antisense RNA transcript specifically expressed in vasopressinergic magnocellular neurons in the rat supraoptic nucleus.

Vasopressin (VP) and oxytocin (OT) play critical roles in the regulation of salt and water balance, lactation, and various behaviors and are expressed at very high levels in specific magnocellular neurons (MCNs) in the hypothalamo-neurohypophysial system (HNS). In addition to the cell-specific expression of the VP and OT genes in these cells, there are other transcripts that are preferentially expressed in the VP or OT MCNs. One such gene, paternally expressed gene 3 (Peg3), is an imprinted gene expressed exclusively from the paternal allele that encodes a Kruppel-type zinc finger-containing protein involved in maternal behavior and is abundantly expressed in the VP-MCNs. We report here the robust expression in the VP-MCNs of an RNA, which we designate APeg3 that is transcribed in the antisense direction to the 3' untranslated region of the Peg3 gene. The APeg3 mRNA is about 1 kb in size, and the full-length sequence of APeg3, as determined by 5' and 3' RACE, contains an open reading frame that predicts a protein of 93 amino acids and is predominantly expressed in VP-MCNs. Both Peg3 and APeg3 gene expression in the VP-MCNs increase during systemic hyperosmolality in vivo, demonstrating that both of these genes are osmoregulated.

Glasgow E ，Ryu SL ，Yamashita M ，Zhang BJ ，Mutsuga N ，Gainer H ... -  《-》